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This is something I've been mulling over while creating an AngularJS app. When I first learned about AngularJS factories, I thought one clever usage of them would be to create and return a constructor function rather than a plain object, i.e. something like:
app.factory("Foo", function() {
function Foo(bar, baz) {
this.bar = bar;
this.baz = baz;
...
}
Foo.prototype = {
constructor: Foo,
method1: function() { ... },
method2: function() { ... },
...,
methodn: function() { ... },
};
return Foo;
});
Then, you could inject the function into your controllers and call it with new. I found this aesthetically pleasing and OOP-y, but now I'm starting to think that it's actually an anti-pattern. The problem is that it works fine for when you're working within AngularJS-aware contexts, but once you want to, for instance, call the constructor from the console, use it in a Web Worker, or reuse the code in a non-AngularJS app, you start having to work around AngularJS rather than with it. I began to wonder if this approach was misguided insofar as functions in javascript already seem to be "singletons" and don't seem to need any help being instantiated.
Am I misusing AngularJS factories? Would I be better served with constructor functions exposed to the global scope? More generally, are there specific factors which promote the usage of AngularJS factories/services/providers over global objects or vice versa?
605
A factory is a simple function which allows us to add some logic to a created object and return the created object. The factory is also used to create/return a function in the form of reusable code which can be used anywhere within the application.
The major difference between an AngularJS service and an AngularJS factory is that a service is a constructor function and a factory is not. That is why, in the case of a factory, we return an object literal instead of using this.
In classical object-oriented programming languages, a constructor is a special method used to initialize a newly created object once memory has been allocated for it. In JavaScript, as almost everything is an object, we're most often interested in object constructors.
The Factory Pattern is a creational design pattern that adds an abstraction layer over common base behaviour between multiple objects of a generic type. The client code, the code that will use this layer, does not need to know the specifics of the implementation of the behaviour, as long as it exists.
Yes!
Factories Syntax: module.factory( 'factoryName', function ); Result: When declaring factoryName as an injectable argument you will be provided the value that is returned by invoking the function reference passed to module.factory. Usage: Could be useful for returning a 'class' function that can then be new'ed to create instances.
Source: https://groups.google.com/forum/#!msg/angular/56sdORWEoqg/HuZsOsMvKv4J
The above link is also used as the source to Bart's comment: AngularJS: Service vs provider vs factory
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