CODEWITHSUNDEEP
angularjsdependency-injection
csvan
csvan

Reputation: 9474

AngularJS DI annotations - why use them?

I am learning AngularJS, and am currently trying master Dependency Injection.

When I define a controller, the documentation tells me that specifying dependencies through annotations, and just listing them in the parameter list for the constructor are equivalent. Hence, I should get the same outcome if I write either:

angular
    .module('myapp.controllers', [])
        .controller('MainNavigationController', ['$scope', '$location', function ($scope, $location) { 
            // ... some code
        }]);

or:

angular
    .module('myapp.controllers', [])
        .controller('MainNavigationController', function ($scope, $location) { 
            // ... some code
        });

Is there any practical reasons I should prefer the former, since it seems to be needlessly verbose?

Upvotes: 1

Views: 81

Answers (2)

Gabriel
Gabriel

Reputation: 872

The former is used for JavaScript minification, which changes parameter names and thus would break the name-based DI. String values "survive" the minification and let Angular "know" which parameter should be bound to which dependency.

You can use the latter and use https://github.com/btford/ngmin to generate the strings array in build time.

Upvotes: 0

Jscti
Jscti

Reputation: 14440

This syntax is needed when you want to keep your dependency injected when minifying your code (var name will be replaced, so dependencies will be affected) :

angular
    .module('myapp.controllers', [])
        .controller('MainNavigationController', function (a, b) { 
            // ... some code
        });

a, b dependencies doesn't exists ... so code will crash

angular
    .module('myapp.controllers', [])
        .controller('MainNavigationController', ['$scope', '$location', function (a, b) { 
            // ... some code
        }]);

a, b are being tied to real dependency string.. OK after minification

See : https://docs.angularjs.org/guide/di

Upvotes: 1

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