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@ngdoc overview
@name Cookbook: MVC
@description
MVC allows for a clean an testable separation between the behavior (controller) and the view
(HTML template). A Controller is just a JavaScript class which is grafted onto the scope of the
view. This makes it very easy for the controller and the view to share the model.
The model is a set of objects and primitives that are referenced from the Scope ($scope) object.
This makes it very easy to test the controller in isolation since one can simply instantiate the
controller and test without a view, because there is no connection between the controller and the
view.
<doc:example>
<doc:source>
<script>
function TicTacToeCntl($scope, $location) {
$scope.cellStyle= {
'height': '20px',
'width': '20px',
'border': '1px solid black',
'text-align': 'center',
'vertical-align': 'middle',
'cursor': 'pointer'
};
$scope.reset = function() {
$scope.board = [
['', '', ''],
['', '', ''],
['', '', '']
];
$scope.nextMove = 'X';
$scope.winner = '';
setUrl();
};
$scope.dropPiece = function(row, col) {
if (!$scope.winner && !$scope.board[row][col]) {
$scope.board[row][col] = $scope.nextMove;
$scope.nextMove = $scope.nextMove == 'X' ? 'O' : 'X';
setUrl();
}
};
$scope.reset();
$scope.$watch(function() { return $location.search().board;}, readUrl);
function setUrl() {
var rows = [];
angular.forEach($scope.board, function(row) {
rows.push(row.join(','));
});
$location.search({board: rows.join(';') + '/' + $scope.nextMove});
}
function grade() {
var b = $scope.board;
$scope.winner =
row(0) || row(1) || row(2) ||
col(0) || col(1) || col(2) ||
diagonal(-1) || diagonal(1);
function row(row) { return same(b[row][0], b[row][1], b[row][2]);}
function col(col) { return same(b[0][col], b[1][col], b[2][col]);}
function diagonal(i) { return same(b[0][1-i], b[1][1], b[2][1+i]);}
function same(a, b, c) { return (a==b && b==c) ? a : '';};
}
function readUrl(value) {
if (value) {
value = value.split('/');
$scope.nextMove = value[1];
angular.forEach(value[0].split(';'), function(row, col){
$scope.board[col] = row.split(',');
});
grade();
}
}
}
</script>
<h3>Tic-Tac-Toe</h3>
<div ng-controller="TicTacToeCntl">
Next Player: {{nextMove}}
<div class="winner" ng-show="winner">Player {{winner}} has won!</div>
<table class="board">
<tr ng-repeat="row in board" style="height:15px;">
<td ng-repeat="cell in row" ng-style="cellStyle"
ng-click="dropPiece($parent.$index, $index)">{{cell}}</td>
</tr>
</table>
<button ng-click="reset()">reset board</button>
</div>
</doc:source>
<doc:scenario>
it('should play a game', function() {
piece(1, 1);
expect(binding('nextMove')).toEqual('O');
piece(3, 1);
expect(binding('nextMove')).toEqual('X');
piece(1, 2);
piece(3, 2);
piece(1, 3);
expect(element('.winner').text()).toEqual('Player X has won!');
});
function piece(row, col) {
element('.board tr:nth-child('+row+') td:nth-child('+col+')').click();
}
</doc:scenario>
</doc:example>
# Things to notice
* The controller is defined in JavaScript and has no reference to the rendering logic.
* The controller is instantiated by <angular/> and injected into the view.
* The controller can be instantiated in isolation (without a view) and the code will still execute.
This makes it very testable.
* The HTML view is a projection of the model. In the above example, the model is stored in the
board variable.
* All of the controller's properties (such as board and nextMove) are available to the view.
* Changing the model changes the view.
* The view can call any controller function.
* In this example, the `setUrl()` and `readUrl()` functions copy the game state to/from the URL's
hash so the browser's back button will undo game steps. See deep-linking. This example calls {@link
api/angular.module.ng.$rootScope.Scope#$watch $watch()} to set up a listener that invokes `readUrl()` when needed.
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