Using method as a filter in AngularJS: A guide to implementing custom filters

Question

Using method as a filter in AngularJS: A guide to implementing custom filters

I've created a custom data type called Message:

function Message(body, author, date) {
    this.body = body;
    this.author = author;
    this.date = date;
    this.stars = [];
}

Message.prototype.hasStars = function() {
    return this.stars.length !== 0;
};

Currently, I am iterating over an array of these messages:

<li ng-repeat='message in messages | orderBy:"-stars.length"'>…</li>

Is there a way to add a filter that utilizes the message.hasStars() method? I attempted several methods below but none seemed to work as expected:

message in messages | filter:message.hasStars() | orderBy:"-stars.length"
message in messages | filter:message:hasStars() | orderBy:"-stars.length"
message in messages | filter:message.hasStars | orderBy:"-stars.length"
message in messages | filter:message:hasStars | orderBy:"-stars.length"

javascript angularjs

Answer 1

Answer №1

http://jsfiddle.net/DGKNN/

filter function in AngularJS requires an expression that acts as a predicate on the scope. This means it needs a function that can take an element as input and determine whether or not the element should be included in the collection.

In your controller:

$scope.hasStars = function (message) {
    return message.hasStars();
};

In your view:

<li ng-repeat='message in messages | filter:hasStars | orderBy:"-stars.length"'>...</li>

Answer 2

http://jsfiddle.net/DGKNN/

filter function in AngularJS requires an expression that acts as a predicate on the scope. This means it needs a function that can take an element as input and determine whether or not the element should be included in the collection.

In your controller:

$scope.hasStars = function (message) {
    return message.hasStars();
};

In your view:

<li ng-repeat='message in messages | filter:hasStars | orderBy:"-stars.length"'>...</li>

Answer 3

Answer №2

I assume that a service named mySrv is responsible for loading messages into your controller.

myapp.controller('myCtrlr',['$scope','mySrv',function($scope,mySrv){
    $scope.messages = mySrv.getMessages();
}]); // end myCtrlr

myapp.filter('hasStars',function(){
    return function(msg){
        return msg.stars.length > 0;
    };
});

When working in the template

<ul ng-controller="myCtrlr">
    <li ng-repeat="message in messages | hasStars | orderBy:"-stars.length">...</li>
</ul>

Answer 4

I assume that a service named mySrv is responsible for loading messages into your controller.

myapp.controller('myCtrlr',['$scope','mySrv',function($scope,mySrv){
    $scope.messages = mySrv.getMessages();
}]); // end myCtrlr

myapp.filter('hasStars',function(){
    return function(msg){
        return msg.stars.length > 0;
    };
});

When working in the template

<ul ng-controller="myCtrlr">
    <li ng-repeat="message in messages | hasStars | orderBy:"-stars.length">...</li>
</ul>

Using method as a filter in AngularJS: A guide to implementing custom filters

Answer №1

Answer №2

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