AngularJS Dependency Injection Principle

Question

What is the magic behind auto resolving dependencies in AngularJS?

angular
    .module('app', [])
    .service('appService', 
        function appService (firstService, secondService, thirdService) { }

How are firstService, secondService, thirdService automatically injected?

Take a look at alexrothenberg.com/2013/02/11/…

Whisher
– Whisher

2014-04-17 11:53:48 +00:00
Commented Apr 17, 2014 at 11:53 — Whisher
– Whisher, Commented Apr 17, 2014 at 11:53

Artem Platonov · Accepted Answer · 2014-04-17 11:12:17Z

1

JavaScript Automatic Dependency Injection is based on Function.prototype.toString() method that returns a string representation of the object in the form of a function declaration.

The returned string is parsed with regular expression to find function arguments and return its names that will be used to find, instantiate and inject real services.

(function appService (firstService,secondService,thirdService) {})
    .toString()
    .match(/^function\s*[^\(]*\(\s*([^\)]*)\)/m)[1]
    .split(',')

// => ["firstService", "secondService", "thirdService"]

answered Apr 17, 2014 at 11:12

Artem Platonov

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