We'll explain in a second how the dependency injector resolves the correct values. You can read more about promises in Please note: this chapter has not yet been released. Instead, even Angular internally always uses the regular dependency injection mechanism to resolve a service's implementation. When called, the factory function creates and returns the service instance. Now that we have the value, let's create the token for it. So what Angular does with dependency injection is something extraordinary from that perspective! You register a provider with a module just like you do with a service or factory, except you use the provider function instead.
Dependency Injection is a software design in which components are given their dependencies instead of hard coding them within the component. It is used to pass values in factories, services or controllers during run and config phase. We've already mentioned that when you create a service via the provider or any of the shortcuts Angular gives you , you create a new provider that defines how that service is constructed. This is the behavior for any complex values objects, functions but not for primitive types. Normally you're doing fine with factorys.
Choosing between a module and the component to register the dependency is based on need. What I didn't mention is that these providers can be injected into config sections of your application so you can interact with them! All Services are singletons; they get instantiated once per app. Let's look at a simple example of how you can create your own service. So let's first understand what a dependency is. So, Angular recognizes the dependencies by their specific parameter names.
In this context, you need to worry about performance impact only if you used a lot of injectable functions in your angular code. Factories, services and controllers can now reference these values by their name. It only knows the contract provided by these objects and how to consume them. Check out this based on Epokk's:. } ; There is one important exception: constants, since they cannot be changed, are allowed to be injected inside config blocks this is how they differ from values. You can read more about modules in general, and how to use them in your code in.
In our controller definition, we are now referencing our 'AdditionService' service. If you looked at the entire function, you will realize that it is capable of handling all the different annotation approaches described above. Every dependency is a key-value pair, where the key is a token and the value is the object of the dependency. There is literally, 100% no difference in the two versions. In the array the last element is the anonymous function while all the elements before are the names of the objects Angular needs to pass to the function in the order it needs to pass them. This time angular uses 'new' keyword and call the constructor function something like below.