An article to talk about dependency injection in Angular

This article will take you to continue learning angular and briefly understand dependency injection in Angular. I hope it will be helpful to you!

Translator added: Wikipedia points out - In software engineering, dependency injection (Dependency Injection, DI) refers to letting an object receive the dependencies it depends on of other objects. "Dependencies" refer to objects required by the receiver. "Injection" refers to the process of passing "dependencies" to the receiver. After "injection", the receiver will call the "dependency".

Translator added: For example - when classA uses some functions of classB, it means classA Has dependencies on classB. Before using classA, we need to create classB. Recommended articleWhat is Dependency Injection? How to use it?

We all know the standard way of using services services in Angular. Mark the service as injectable and put it in the provider section in the module. As follows:

For dependency injection, we have many tricks that we can use. For example, in the module Angular you can convert a line TestService to a different line of writing. [Recommended related tutorials: angular tutorial, Programming teaching]

We put it in the provider section Each service is converted into an object with two properties. In the provide attribute we can use the class name or we can create a unique key and inject an object. We can even inject a variable.

Another interesting feature is that we can inject multiple objects with the same key and use them like an array.

And, we can also inject different services according to different situations. In other words, we can use the if-else statement.

Now, I hope you understand the charm of Angular dependency injection.

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This article is a translation, in the form of free translation. Original address: # Angular dependency injection

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