Code-In

reposted from jigyasagrover.wordpress.com/tictactoe-tutorial-funwithpharo This tutorial has been included as a chapter in  Fun With Pharo! Tic-tac-toe (or Noughts and crosses, Xs and Os) is a paper-and-pencil game for two players, X and O, who take turns marking the spaces in a 3×3 grid. The player who succeeds in placing three respective marks in a horizontal, vertical, or diagonal row wins the game. Because of the simplicity of Tic-tac-toe, it is often used as a pedagogical tool for teaching the concepts of good sportsmanship and the branch of artificial intelligence that deals with the searching of game trees. It is straightforward to write a computer program to play Tic-tac-toe perfectly, to enumerate the 765 essentially different positions (the state space complexity), or the 26,830 possible games up to rotations and reflections (the game tree complexity) on this space. So , here we make a Pharo version of this well-known game by using Morph. This post provides a step-by-step approach on how to go about building this simple application. A game package will be built having 3 subclasses : TicTacToe TicTacToeCell TicTacToeModel Initially , we have created TicTacToe a subclass of the Object class. The subclasses we will make will be combined in the package game as mentioned in the category: parameter. Object subclass: #TicTacToe instanceVariableNames: 'container model' classVariableNames: '' poolDictionaries: '' category: 'game' A category name is not required in order for the class to work, but you will not be able to access the class to make changes or to look at existing code unless you provide a category name. (The category name used can be a new category name or the name of an existing category.) The poolDictionaries: parameter is seldom used and will not be discussed here, and the category: parameter specifies the category under which this class will be grouped in the system browser. As we know, a class encapsulates data values and methods, and every object contains a set of the data values and can receive any of the methods as a message. The data values in each object are specified by providing a set of names of variables whose values will be an object's internal data values. Each object has its own set of these values, and the set of data values for an object represents the object's state (or value). The variables that contain the data values of an object are called the instance variables for the object, and the instanceVariableNames: parameter is a list of names, separated by blanks, for the instance variables. In the above code snippet , we have declared container and model as two instanceVariables. The classVariableNames: parameter lists the identifiers that are the names of variables shared by the class and all of its objects. That is, there is only one set of these, and they are used by the class and all of its objects. Class variables (so called because they belong to the class, of which there is only one, rather than to the objects that are…