Injectables

We can define provider using the @Injectable decorator. It creates an implicit provider for us to create an instance of the decorated class. We define the class dependencies (its constructor arguments) using the deps property of the injectable decorator argument or using the @Dependencies decorator.

In the following examples, we define a service class SomeService that depends on a value identified by the token "token" and another service identified by the token OtherService, which is the class name of another injectable service.

Example using deps property:

import {Injectable, Dependencies} from "@chojs/core";

@Injectable({
    deps: ["token", OtherService],
})
class SomeService {
    constructor(readonly token: string,
                readonly service: OtherService) {
    }
}

Example using @Dependencies decorator:

import {Injectable, Dependencies} from "@chojs/core";

@Injectable()
@Dependencies("token", OtherService)
class SomeService {
    constructor(readonly token: string,
                readonly service: OtherService) {
    }
}

The example above is equivalent to following example using explicit provider definition:

import {Injectable} from "@chojs/core";

@Injectable({
    deps: ["token", OtherService],
})
class SomeService {
}

const provider = {
    provide: SomeService,
    factory: async (injector) => {
        const a = await injector.resolve("token");
        const b = await injector.resolve(OtherService);
        return new SomeService(a, b);
    },
};