Adding an Edit Route for Access Codes in Open Event Frontend

This blog post will illustrate how to add edit route to access code to allow organizers editing an access code. Editing access codes deals with the following API on Open Event Server.

PATCH          /v1/access-codes/{id}

First of all we need to add a route to allow editing of access codes. Our route will be /events/{event_id}/tickets/access-codes/edit/{access_code_id}. To generate a new route we need to run the command

ember g route events/view/tickets/access-codes/edit

This will generate new routes files and templates. Also this will add this route in router.js. In router.js we need to specify what we are passing as a parameter to route. For this we specify access_code_id to let ember know that this parameter will be passed with the URL. This is done so as to know which access code to update. Our route should look something like this /events/{event_id}/tickets/access-codes/edit/{access_code_id}. Final router.js file for access-codes part is given below:

//  app/router.js
 
this.route('access-codes', function() {
   this.route('list', { path: '/:access_status' });
   this.route('create');
   this.route('edit', { path: '/edit/:access_code_id' });
});

 

Next we need to pass model (data) to our edit route template. In our model we will be looking for a particular access code with an id and event tickets. After we get our event tickets, we then look for the event tickets which are already present in that access code. This is done so as to check the tickets in the template which are already present in that access code. So for this in afterModel hook we loop over all event tickets and whichever ticket is included in the access code tickets array we mark its isChecked property as true. This helps us to mark those tickets as checked in multiple select checkboxes of template.

// app/routes/events/view/tickets/access-codes/edit.js

model(params) {
   return RSVP.hash({
     accessCode : this.store.findRecord('access-code', params.access_code_id, {}),
     tickets    : this.modelFor('events.view').query('tickets', {})
   });
 },

 async afterModel(model) {
   let tickets = await model.accessCode.tickets;
   let allTickets = model.tickets;
   allTickets.forEach(ticket => {
     if (tickets.includes(ticket)) {
       ticket.set('isChecked', true);
     } else {
       ticket.set('isChecked', false);
     }
   });

 

The information about multiple select checkboxes in frontend has been discussed in this blog post. Now after we are done setting our edit route we need to redirect user to edit page when he/she clicks on the edit button in access code list. For this we define the necessary actions in template which will be triggered when user clicks on the icon. Code for the edit icon in access code list is given below.

// templates/components/ui-table/cell/events/view/tickets/access-codes/cell-actions.hbs

class="ui vertical compact basic buttons"> {{#ui-popup content=(t 'Edit') click=(action editAccessCode record.id) class='ui icon button' position='left center'}} class="edit icon"> {{/ui-popup}}

 

The editAccessCode action looks something like this.

// controller/events/view/tickets/access-codes/edit.js

editAccessCode(id) {
     this.transitionToRoute('events.view.tickets.access-codes.edit', id);
}

 

After clicking on the edit icon user is redirected to edit route where he/she can edit access code choosen. We use the same component that we chose for creating access code. To know more about create access code template component refer to this blog. Finally when saving the edited access code we call save action. This action is defined in the controllers. The action looks something like this.

// controllers/events/view/tickets/access-codes/edit.js

export default Controller.extend({
 actions: {
   save(accessCode) {
     accessCode.save()
       .then(() => {
         this.get('notify').success(this.get('l10n').t('Access code has been successfully updated.'));
         this.transitionToRoute('events.view.tickets.access-codes');
       })
       .catch(() => {
         this.get('notify').error(this.get('l10n').t('An unexpected error has occured. Discount code cannot be created.'));
       });
   }
 }
});

 

After the access code is saved. We redirect user back to access code list.

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Modifying Tickets API in Open Event Server to Return Hidden Tickets Only for Organizers and Admins

This blog article will illustrate how we can modify the permissions settings for an API to enable different kind of responses to users with different level of permissions. In this article we will discuss these changes with respect to Tickets API.

Initially we had a query where we were returning only those tickets who were set to be visible by the admin. Query for this was:

class TicketList(ResourceList):
   """
   List Tickets based on different params
   """
   def before_get(self, args, view_kwargs):
       """
       before get method to get the resource id for assigning schema
       :param args:
       :param view_kwargs:
       :return:
       """
       if view_kwargs.get('ticket_tag_id') or view_kwargs.get('access_code_id') or         view_kwargs.get('order_identifier'):
           self.schema = TicketSchemaPublic

   def query(self, view_kwargs):
       """
       query method for resource list
       :param view_kwargs:
       :return:
       """


       query_ = self.session.query(Ticket).filter_by(is_hidden=False)

 

Problem with this query was that this returned same response irrespective of who is logged in. Hence even the organizers were not able to modify hidden tickets because they were not returned by server.

Solution to this problem was to provide hidden tickets only to those who are organizer or are admin/super admins. For this we used the JWT token that was being sent from frontend in request headers for each authenticated request that was being made from frontend.

We modified the code to something like this:

class TicketList(ResourceList):
   """
   List Tickets based on different params
   """
   def before_get(self, args, view_kwargs):
       """
       before get method to get the resource id for assigning schema
       :param args:
       :param view_kwargs:
       :return:
       """
       if view_kwargs.get('ticket_tag_id') or view_kwargs.get('access_code_id') or view_kwargs.get('order_identifier'):
           self.schema = TicketSchemaPublic

   def query(self, view_kwargs):
       """
       query method for resource list
       :param view_kwargs:
       :return:
       """

       if 'Authorization' in request.headers:
           _jwt_required(current_app.config['JWT_DEFAULT_REALM'])
           if current_user.is_super_admin or current_user.is_admin:
               query_ = self.session.query(Ticket)
           elif view_kwargs.get('event_id') and has_access('is_organizer', event_id=view_kwargs['event_id']):
               query_ = self.session.query(Ticket)
           else:
               query_ = self.session.query(Ticket).filter_by(is_hidden=False)
       else:
           query_ = self.session.query(Ticket).filter_by(is_hidden=False)

 

Here we added some conditions which were used to check permission level of logged in user. After picking JWT token from request headers we check if the user was admin or super_admin, then we return all the tickets without any condition. Then we also check if the logged in user was organizer of event then also we send all the tickets without any conditions.

However if request comes from unauthenticated users (without valid token) or users with normal privileges, then we returned tickets whose isHidden property was set to False. The functions such as is_organizer and is_super_admin acted as helpers as they were imported from other helper files where they were defined.

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How We Implement Custom Forms for Sessions and Speaker Form in Open Event Frontend

In this blog we will see the implementation of custom form for session and speakers form. Since every event organiser requires different fields required to be filled by speakers for their sessions, for ex. Some event organiser may need GitHub profile whereas other may need LinkedIn profile so, we implemented custom form for session and speaker form in Open Event Frontend so that every organiser can choose fields he/she requires to be filled by his speakers who are filling their proposal. Custom form allows following features:

  1. Allows organiser to choose whether he wants a particular field or not.
  2. Organiser can make a field compulsory, so that no speaker can submit his proposal without filling that field.

So, to get started we define our getCustomForm() method in mixins and it looks something like this:

import Mixin from '@ember/object/mixin';
import MutableArray from '@ember/array/mutable';

export default Mixin.create(MutableArray, {

 getCustomForm(parent) {
   return [
     this.store.createRecord('custom-form', {
       fieldIdentifier : 'title',
       form            : 'session',
       type            : 'text',
       isRequired      : true,
       isIncluded      : true,
       isFixed         : true,
       event           : parent
     }),
     this.store.createRecord('custom-form', {
       fieldIdentifier : 'subtitle',
       form            : 'session',
       type            : 'text',
       isRequired      : false,
       isIncluded      : false,
       event           : parent
     }),
     this.store.createRecord('custom-form', {
       fieldIdentifier : 'shortAbstract',
       form            : 'session',
       type            : 'text',
       isRequired      : false,
       isIncluded      : true,
       event           : parent
     }),

...

 

Here we define all the possible fields with their properties. Every field has different properties that enables us to identify whether to choose or reject them. So to enable this these fields to be chosen by organiser we need to feed them into model.

In our session-speakers-step.js in components we assign these fields to our model thorugh this:

didInsertElement() {
   if (this.get('data.event.customForms')&&!his.get('data.event.customForms.length')) {
     this.set('data.event.customForms', this.getCustomForm(this.get('data.event')));
   }
}

 

This hook gets called when our component is rendered and custom form fields gets assigned to data.event.customForms in our model.

In our handlebars template we create sliders to enable organiser to choose whether he wants to enable a field or not.

In our template logic we write a loop that renders these sliders for each fields and manipulate them as organiser slides any slider for a field. Let’s take a look at the template code block:

       <tbody>
           {{#each customForm.session as |field|}}
             <tr class="{{if field.isIncluded 'positive'}}">
               <td class="{{if device.isMobile 'center' 'right'}} aligned">
                 <label class="{{if field.isFixed 'required'}}">
                   {{field.name}}
                 </label>
               </td>
               <td class="center aligned">
                 {{ui-checkbox class='slider'
                               checked=field.isIncluded
                               disabled=field.isFixed
                               onChange=(action (mut field.isIncluded))
                               label=(if device.isMobile (t 'Include'))}}
               </td>
               <td class="center aligned">
                 {{ui-checkbox class='slider'
                               checked=field.isRequired
                               disabled=field.isFixed
                               onChange=(action (mut field.isRequired))
                               label=(if device.isMobile (t 'Require'))}}
               </td>
             </tr>
           {{/each}}
         </tbody>

 

Every slider has a action attached to it that manipulates a property of the custom for and on proceeding it saves the custom form model to server.

Later on when rendering for for speaker we fetch details from server about which fields are required or not.

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How RSVP Handles Promises in Open Event Frontend

This blog post illustrates how to manage multiple promises simultaneously using a library known as RSVP in Open Event frontend.

What are Promises?

Promises are used to manage synchronous calls in javascript. Promises represent a value/object that may not be available yet but will become available in near future. To quote from MDN web docs:

The Promise object represents the eventual completion (or failure) of an asynchronous operation, and its resulting value.

What about RSVP?

Rsvp is a lightweight library used to organize asynchronous code. Rsvp provides several ways to handle promises and their responses. A very simple promise implementation using rsvp looks something like this.

var RSVP = require('rsvp');

var promise = new RSVP.Promise(function(resolve, reject) {
  // succeed
  resolve(value);
  // or reject
  reject(error);
});

promise.then(function(value) {
  // success
}).catch(function(error) {
  // failure
});

 

It’s simple, right? So, what it is doing is after it defines a promise it assumes two possible states of a promise which are resolve or reject and after promise has completed it executes the respective function.

Use in Open Event Frontend?

Almost all calls to open event server APIs are done asynchronously. One of the most significant use of rsvp comes when handling multiple promises in frontend and we want all of them to be evaluated at together. Unlike normal promises where each promises resolved or rejected individually, rsvp provides a promise.all() method which accepts array of promises and evaluates all at once. It then calls resolve or reject based on the status of all promises. A typical example where we use promise.all() is given here.

import Controller from '@ember/controller';
import RSVP from 'rsvp';
import EventWizardMixin from 'open-event-frontend/mixins/event-wizard';

export default Controller.extend(EventWizardMixin, {
 actions: {
   save() {
     this.set('isLoading', true);
     this.get('model.data.event').save()
       .then(data => {
         let promises = [];
         promises.push(this.get('model.data.event.tickets').toArray().map(ticket => ticket.save()));
         promises.push(this.get('model.data.event.socialLinks').toArray().map(link => link.save()));
         if (this.get('model.data.event.copyright.licence')) {
           let copyright = this.setRelationship(this.get('model.data.event.copyright.content'), data);
           promises.push(copyright.save());
         }
         if (this.get('model.data.event.tax.name')) {
           let tax = this.setRelationship(this.get('model.data.event.tax.content'), data);
           if (this.get('model.event.isTaxEnabled')) {
             promises.push(tax.save());
           } else {
             promises.push(tax.destroyRecord());
           }
         }
         RSVP.Promise.all(promises)
           .then(() => {
             this.set('isLoading', false);
             this.get('notify').success(this.get('l10n').t('Your event has been saved'));
             this.transitionToRoute('events.view.index', data.id);
           }, function() {
             this.get('notify').error(this.get('l10n').t('Oops something went wrong. Please try again'));
           });
       })
       .catch(() => {
         this.set('isLoading', false);
         this.get('notify').error(this.get('l10n').t('Oops something went wrong. Please try again'));
       });
   },
}

 

Here we made array of promises and then pushed each of the promises to it. Then at the end used this array of promises in RSVP.promise.all() which then evaluated it based on success or failure of the promises.

Resources:
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Loading Default System Image of Event Topic on Open Event Server

In this blog, we will talk about how to add feature of loading system image of event topic from server to display it on Open Event Server. The focus is on adding a helper function to create system image and loading that local image onto server.

Helper function

In this feature, we are providing feature of addition of loading default system image if user doesn’t provides that.

  1. First we get a suitable filename for a image file using get_file_name() function.
  2. After getting filename, we check if the url provided by user is a valid url or not.
  3. If the url is invalid then we use the default system image as the image of that particular event topic.
  4. After getting the local image then we read that image, if the given image file or the default image is not readable or gives IOError then we send a message to the user that Image url is invalid.
  5. After successful reading of image we upload the image to event_topic directory in static directory of the project.
  6. After uploading of this image we get a local URL which shows where is the image is stored. This path is stored into database and finally we can display this image.

Resources

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Adding Custom System Roles API on Open Event Server

In this blog, we will talk about how to add API for accessing the Custom System Roles on Open Event Server. The focus is on Schema creation and it’s API creation.

Schema Creation

For the CustomSystemRoleSchema, we’ll make our Schema as follows

Now, let’s try to understand this Schema.

In this feature, we are providing Admin the rights to get and create more system roles.

  1. First of all, we are provide the two fields in this Schema, which are id and name.
  2. The very first attribute id should be of type string as it would have the identity which will auto increment when a new system role is created. Here dump_only means that this value can’t be changed after the record is created.
  3. Next attribute name should be of string type and it will contain the name of new custom system role. This attribute is required in a custom_system_roles table.

API Creation

For the Custom System Roles, we’ll make our API as follows

Now, let’s try to understand this Schema.

In this API, we are providing Admin the rights to set Custom System roles.

  1. CustomSystemRoleList inherits ResourceList which will give us list of all the custom system roles in the whole system.
  2. CustomSystemRoleList has a decorators attribute which gives the permission of POST request to only admins of the system.
  3. CustomSystemRoleDetail inherits ResourceDetail which will give the details of a CustomSystemRole object by id.
  4. CustomSystemRoleDetail has a decorators attribute which gives the permission of PATCH and DELETE requests to only admins of the system.

So, we saw how Custom System Role Schema and API is created to allow users to get it’s values and Admin users to update and delete it’s record.

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Adding Panel Permissions API in Open Event Server

In this blog, we will talk about how to add API for accessing the Panel Permissions on Open Event Server. The focus is on Schema creation and it’s API creation.

Schema Creation

For the PanelPermissionSchema, we’ll make our Schema as follows

Now, let’s try to understand this Schema.

In this feature, we are providing Admin the rights to create and assign panel permission to any of the custom system role.

  1. First of all, we are provide the four fields in this Schema, which are id, panel_name, role_id and can_access.
  2. The very first attribute id should be of type string as it would have the identity which will auto increment when a new system role is created. Here dump_only means that this value can’t be changed after the record is created.
  3. Next attribute panel_name should be of string type and it will contain the name of panel. This attribute is required in a panel_permissions table so set as allow_none=False.
  4. Next attribute role_id should be of integer type as it will tell us that to which role current panel is concerning.
  5. Next attribute can_access should be of boolean type as it will tell us whether a role of id=role_id has access to this panel or not.
  6. There is also a relationship named role which will give us the details of the custom system role with id=role_id.

API Creation

For the Panel Permissions, we’ll make our API as follows

Now, let’s try to understand this Schema.

In this API, we are providing Admin the rights to set panel permissions for a custom system role.

  1. PanelPermissionList inherits ResourceList which will give us list of all the custom system roles in the whole system.
  2. PanelPermissionList has a decorators attribute which gives the permission of both GET and POST requests to only admins of the system.
  3. The POST request of PanelPermissionList API requires the relationship of role.
  4. PanelPermissionDetail inherits ResourceDetail which will give the details of a Panel Permission object by id.
  5. PanelPermissionDetail has a decorators attribute which gives the permission of GET, PATCH and DELETE requests to only admins of the system.

So, we saw how Panel Permissions Schema and API is created to allow Admin users to get, update and delete it’s record.

Resources

 

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Adding device names’ support for check-ins to Open Event Server

The Open Event Server provides backend support to Open Event Organizer Android App which is used to check-in attendees in an event. When checking in attendees, it is important for any event organizer to keep track of the device that was used to check someone in. For this, we provide an option in the Organizer App settings to set the device name. But this device name should have support in the server as well.

The problem is to be able to add device name data corresponding to each check-in time. Currently attendees model has an attribute called `checkin-times`, which is a csv of time strings. For each value in the csv, there has to be a corresponding device name value. This could be achieved by providing a similar csv key-value pair for “device-name-checkin”.

The constraints that we need to check for while handling device names are as follows:

  • If there’s `device_name_checkin` in the request, there must be `is_checked_in` and `checkin_times` in the data as well.
  • Number of items in checkin_times csv in data should be equal to the length of the device_name_checkin csv.
  • If there’s checkin_times in data, and device-name-checkin is absent, it must be set to `-` indicating no set device name.
if ‘device_name_checkin’ in data and data[‘device_name_checkin’] is not None:
  if ‘is_checked_in’ not in data or not data[‘is_checked_in’]:
       raise UnprocessableEntity(
           {‘pointer’: ‘/data/attributes/device_name_checkin’},
           “Attendee needs to be checked in first”
       )
  elif ‘checkin_times’ not in data or data[‘checkin_times’] is None:
      raise UnprocessableEntity(
          {‘pointer’: ‘/data/attributes/device_name_checkin’},
           “Check in Times missing”
      )
  elif len(data[‘checkin_times’].split(“,”)) != len(data[‘device_name_checkin’].split(“,”)):
     raise UnprocessableEntity(
           {‘pointer’: ‘/data/attributes/device_name_checkin’},
           “Check in Times missing for the corresponding device name”
         )
 if ‘checkin_times’ in data:
   if ‘device_name_checkin’ not in data or data[‘device_name_checkin’] is None:
       data[‘device_name_checkin’] = ‘-‘

The case is a little different for a PATCH request since we need to check for the number of items differently like this:

if ‘device_name_checkin’ in data and data[‘device_name_checkin’] is not None:
            if obj.device_name_checkin is not None:
               data[‘device_name_checkin’] = ‘{},{}’.format(obj.device_name_checkin, data[‘device_name_checkin’])                                                   
            if len(data[‘checkin_times’].split(“,”)) != len(data[‘device_name_checkin’].split(“,”)):
               raise UnprocessableEntity(
                   {‘pointer’: ‘/data/attributes/device_name_checkin’},
                   “Check in Time missing for the corresponding device name”)

Since we expect only the latest value to be present in a PATCH request, we first add it to the object by formatting using:

'{},{}'.format(obj.device_name_checkin, data['device_name_checkin'])

and then compare the length of the obtained CSVs for check in times and device names, so that corresponding to each check in time, we have either a device name or the default fill in value ‘-’.

That’s all. Read the full code here.

Requests and Responses:

Resources

  1. SQLAlchemy Docs
    https://docs.sqlalchemy.org/en/latest/
  2. Alembic Docs
    http://alembic.zzzcomputing.com/en/latest/
  3. Flask REST JSON API Classical CRUD operation
    https://flask-rest-jsonapi.readthedocs.io/en/latest/quickstart.html#classical-crud-operations
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Adding Events’ Payment Preferences to Eventyay Organizer Android App

The Open Event Organizer Android App allows creating events from the app itself. But organizers had to enter the payment information every time. To solve this problem, the PR#1058 was opened which saves the Organizers’ payment preferences in Event Settings.

The Open Event project offers 5 types of payment options:

Online:
1. Paypal
2. Stripe

Offline:
3. Cash payment
4. Bank Transfer
5. Cheques

Each of the above need the payment specific details to be saved. And stuffing all of them into a single Event Settings screen isn’t a good option. Therefore the following navigation was desired:

Event Settings -> Payment Preferences -> All options with their preferences

Android Developer guide references a simple method to achieve the above, which is by using nested preference screens. But unfortunately, there’s a bug in the support library and it cannot be implemented with  PreferenceFragmentCompat

So we had to apply a hack to the UI. We set an OnPreferenceClickListener as follows:

public class EventSettingsFragment extends PreferenceFragmentCompat {
   …
   @Override
   public void onCreatePreferencesFix(@Nullable Bundle bundle, String rootKey) {
       …

       findPreference(“payment_preferences”).setOnPreferenceClickListener(preference -> {
           FragmentTransaction transaction = getFragmentManager().beginTransaction();
           transaction
               .replace(R.id.fragment_container, PaymentPrefsFragment.newInstance())
               .addToBackStack(null)
               .commit();
           return true;
       });
   }
   …
}

Once the preference item “Payment Preferences” is clicked, we initiate a fragment transaction opening the Payment Preferences screen, and add it to the fragment back stack.

For each payment option, we have two things to consider:

  1. Is that payment option supported by the organizer?
  2. If yes, we need to store the necessary details in order to direct the payment to the organizer.

We are also keeping track of whether the organizer wants to keep using the same payment preferences for future events as well. This way we save the organizer’s effort of entering payment details for each new event.

<?xml version=“1.0” encoding=“utf-8”?>
<PreferenceScreen xmlns:android=“http://schemas.android.com/apk/res/android”>

   <CheckBoxPreference
       android:key=“use_payment_prefs”
       android:title=“@string/use_payment_prefs”
       android:summaryOn=“@string/using_payment_preferences”
       android:summaryOff=“@string/not_using_payment_preferences”
       android:defaultValue=“false” />

   <PreferenceCategory
       android:title=“Bank Transfer”>
       <CheckBoxPreference
           android:key=“accept_bank_transfers”
           android:title=“@string/accept_payment_by_bank_transfer”
           android:defaultValue=“false”/>

       <EditTextPreference
           android:key=“bank_details”
           android:title=“@string/bank_details” />
   </PreferenceCategory>
   …

</PreferenceScreen>

Now the only thing remaining is to set payment preferences once the Event Creation form is opened. Hence the following method is called in  CreateEventPresenter  sets the payment details for each option that the organizer has already saved the information for. It does this by using constants named like PREF… all declared in the  Constants.java  file.

using a custom Preference class which abstracts away some boilerplate code for us.

   public void setPaymentPreferences(Preferences preferences) {

       if (preferences.getBoolean(PREF_USE_PAYMENT_PREFS, false)) {
           
           event.setCanPayByBank(
               preferences.getBoolean(PREF_ACCEPT_BANK_TRANSFER, false)
           );
           event.setBankDetails(
               preferences.getString(PREF_BANK_DETAILS, null)
           );
           …
           getView().setPaymentBinding(event);
       }
   }

This is how the result looks like:

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Create Call for Speakers with Open Event Organizer Android App

In The Open Event Organizer Android app, we were providing variety of features to the user but the functionality to create call for speakers for an Event was missing. This feature was required to attract speakers from all over the world to participate in the event and make it a success. Theis blog explains how we added this feature to the project us following MVVM Architecture and using libraries like Retrofit, RxJava, Db Flow etc.

Objective

The goal will be to provide an option to the organizer to create Call for Speakers for an Event (if it doesn’t exist already). We will provide the organizer a Floating Action Button in Speakers Call detail layout which will open a fragment which contain all the relevant fields provided by Open Event Server. The organizer can fill up all the fields as per requirement and create the call for speakers.

Specifications

Let’s move on to the implementation details.

First, we will create the model which will contain all the fields offered by server. We are using Lombok library to reduce boilerplate code using annotations. For example, @Data annotation is used to generate getters and setters. @NoArgsConstructor to generate no arguments constructor as the name suggests. Along with that we are using @JonNaming annotation provided by Jackson library to serialize the model using KebabCaseStrategy. Also, the Table annotation provided by Raziz DbFlow library to make a table in database for this model.

@Data
@Type(“speakers-call”)
@NoArgsConstructor
@JsonNaming(PropertyNamingStrategy.KebabCaseStrategy.class)
@Table(database = OrgaDatabase.class, allFields = true)
public class SpeakersCall {@Id(LongIdHandler.class)
@PrimaryKey
public Long id;@Relationship(“event”)
@ForeignKey(onDelete = ForeignKeyAction.CASCADE)
public Event event;

public String announcement;
public String hash;
public String privacy;
public String startsAt;
public String endsAt;
}

To handle this problem we will be using Retrofit 2.3.0 to make Network Requests, which is a REST client for Android and Java by Square Inc. It makes it relatively easy to retrieve and upload JSON (or other structured data) via a REST based Web Service. Also we will be using other awesome libraries like RxJava 2.1.10 (by ReactiveX) to handle tasks asynchronously, Jackson, Jasminb-Json-Api in an MVVM architecture.

We will make a POST request to the server . So we specify the declaration in SpeakersCallApi.java

@POST(“speakers-calls”)
Observable<SpeakersCall> postSpeakersCall(@Body SpeakersCall speakersCall);

We will use the method createSpeakersCall(SpeakersCall speakersCall) in SpeakersCallRepositoryImpl.java to interact with the SpeakersCallApi and make the network request for us. The response will be passed on to the SpeakersCallViewModel method which calls it.

@Override
public Observable<SpeakersCall> createSpeakersCall(SpeakersCall speakersCall) {
if (!repository.isConnected()) {
return Observable.error(new Throwable(Constants.NO_NETWORK));
}return speakersCallApi
.postSpeakersCall(speakersCall)
.doOnNext(created -> {
created.setEvent(speakersCall.getEvent());
repository
.save(SpeakersCall.class, created)
.subscribe();
})
.subscribeOn(Schedulers.io())
.observeOn(AndroidSchedulers.mainThread());
}

Next, we will see the code for SpeakersCallViewModel which is using MVVM ViewModel to handle the processing logic for SpeakesCallFragment. Here we are passing SpeakersCallRepository instance in constructor. Methods like getProgress, getError and getSuccess pass on a LiveData Object from ViewModel to Fragment and the latter observes the changes on the object and show these in UI. CreateSpeakersCall method is used to call speakersCallRepository to send a POST request to server asynchronously using Retrofit and RxJava. Further, initialize method is used to set initial values of time and date to SpeakersCall object.

public class CreateSpeakersCallViewModel extends ViewModel {
public void createSpeakersCall(long eventId) {
if (!verify())
return;Event event = new Event();event.setId(eventId);
speakersCallLive.getValue().setEvent(event);

compositeDisposable.add(speakersCallRepository.createSpeakersCall(speakersCallLive.getValue())
.doOnSubscribe(disposable -> progress.setValue(true))
.doFinally(() -> progress.setValue(false))
.subscribe(var -> success.setValue(“Speakers Call Created Successfully”),
throwable -> error.setValue(ErrorUtils.getMessage(throwable))));
}
}

We will create a Fragment class to bind the UI elements to the Model class so that they can be processed by ViewModel. The creation form contains less fields therefore BaseBottomSheetFragment is used. In the onStart method, we are binding several LiveData objects like SpeakersCall, Progress, Error, Success to the UI and then observe changes in them. Using LiveData we don’t have to write extra code to handle screen rotation and to update UI when the binded object is modified.

public class CreateSpeakersCallFragment extends BaseBottomSheetFragment implements CreateSpeakersCallView {
@Override
public void onStart() {
super.onStart();
createSpeakersCallViewModel.getSpeakersCall().observe(this, this::showSpeakersCall);
createSpeakersCallViewModel.getProgress().observe(this, this::showProgress);
createSpeakersCallViewModel.getError().observe(this, this::showError);
createSpeakersCallViewModel.getSuccess().observe(this, this::onSuccess);
createSpeakersCallViewModel.initialize();
}
}

We will design the speaker create form using Two Way Data Binding to bind SpeakersCall object to the UI and use TextInputEditText to take user Input. Along with that we have used Time and Date pickers to make it easier to select Date and Time. For viewing the complete code, please refer here.

Thus, we are able to build a responsive, reactive UI using Android Architectural Components.

References

  1. Official documentation of Retrofit 2.x http://square.github.io/retrofit/
  2. Official documentation for RxJava 2.x https://github.com/ReactiveX/RxJava
  3. Official documentation for ViewModel https://developer.android.com/topic/libraries/architecture/viewmodel
  4. Codebase for Open Event Orga App https://github.com/fossasia/open-event-orga-app
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