AngularJS controllers and $scope are essential components in structuring and

As a newcomer to Angular, I've spent some time reading up on scopes and controllers, but I still feel like something isn't quite clicking for me.

Let's take a look at this code snippet:

    var myApp = angular.module("myApp", []);
    myApp.controller("myCtrl", function($scope) {

        $scope.array = [1,2,3];

        $scope.show = false;
        $scope.toggle = function (){
            $scope.show = !$scope.show;
            console.log($scope.show);
        };
    });

Now, let's examine the markup:

<body ng-app="myApp">
<ul ng-controller="myCtrl">
    <li ng-repeat="n in array">
        <a href="#" ng-click="show = !show">Click here to show</a>
        <span ng-show="show">Something to show</span>
    </li>
</ul>
</body>

While using "ng-click='show = !show'" works fine with ng-show, trying to use the toggle() method doesn't. How can I adjust the code to make toggle() work? How do I access the correct scope within the controller? Is it necessary to have ng-controller="myCtrl" on every li tag? Should each scope created by directives in my markup have its own controller? What is considered best practice in this scenario?

Answer №1

It is a fact that the show within the ngRepeat differs from the one in myCtrl. Even if they were the same, having only one variable show in myCtrl would result in all items being hidden or shown together when toggling.

If you wish to toggle individual rows separately, each row needs its own flag. There are various methods to achieve this task. To keep the view logic simple and eliminate the use of $parent, using the controller as syntax with a list of show flags can be employed, utilizing ngRepeat's array index as $index.

var myApp = angular.module("myApp", []);
myApp.controller("myCtrl", function() {
    var myCtrl = this;
    myCtrl.array = [1,2,3];
    myCtrl.show = [false, false, false];

    myCtrl.toggle = function (index){
        myCtrl.show[index] = !myCtrl.show[index];
        console.log(myCtrl.show);
    };
});

The corresponding view:

<body ng-app="myApp">
<ul ng-controller="myCtrl as ctrl">
    <li ng-repeat="n in ctrl.array">
        <a href="#" ng-click="ctrl.toggle($index)">Click here to show</a>
        <span ng-show="ctrl.show[$index]">Something to show</span>
    </li>
</ul>
</body>

An alternative approach involves using an array of objects if dealing with complex tasks where managing two arrays could be challenging. For instance:

myCtrl.array = [
  {val: 1, show: false},
  {val: 2, show: false},
  {val: 3, show: false},
];

The toggle function would then be:

myCtrl.toggle = function(obj){
  obj.show = !obj.show;
};

and the accompanying view:

<body ng-app="myApp">
<ul ng-controller="myCtrl as ctrl">
    <li ng-repeat="n in ctrl.array">
        <a href="#" ng-click="ctrl.toggle(n)">Click here to show</a>
        <span ng-show="n.show">Something to show</span>
    </li>
</ul>
</body>

Edit: Here are plunkr links for both methods.

http://plnkr.co/edit/sBhY00c5LU4YMeHlqjG7?p=preview

http://plnkr.co/edit/axO9sEB6oHQeDwIRLU4a?p=preview

Answer №2

The reason for the strange behavior is due to the fact that ngRepeat creates a separate scope for each iteration. This means that any variables created inside the loop only exist within that specific scope.

By using show = !show, you are actually creating a new variable called show within the child scope of the iteration, rather than toggling an existing one.

Attempting to call toggle as a method directly will not work because it does not belong to the current scope.

If you want to toggle the visibility of individual rows, you can try using $parent.toggle() within the click event handler. However, keep in mind that this will affect the show value in the parent scope, impacting all rows at once.

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