Switching to Angular - Third Edition

Introducing forward references

Angular introduced the concept of forward references. It is required because of the following reasons:

• ES2015 classes are not hoisted
• Allowing resolution of the dependencies that are declared after the declaration of the dependent providers

In this section, we will explain the problem that forward references solve and the way we can take advantage of them.

Now, let's suppose that we have defined the Buffer and Socket classes in the opposite order:

// ch6/injector-basics/forward-ref/app.ts @Injectable() class Socket { constructor(private buffer: Buffer) {...} } // undefined console.log(Buffer); class Buffer { constructor(@Inject(BUFFER_SIZE) private size: Number) {...} } // [Function: Buffer] console.log(Buffer); ...