Providers

Server Enviroment
Client Enviroment

Overview

Providers are a fundamental concept in the Mango Framework. Many of the basic Mango Framework classes can be treated as providers - services, repositories, factories, helpers, and so on. The main idea of a provider is that it can be injected into a class that depends on it during application execution.

Injectable Classes

Services are a great way to share information between classes that don't know each other. They can be injected into controllers, other services, and even custom providers.

For example, you could create an injectable class that returns when a mango is ripe.

@Injectable()
export class MangoRipenessCheckerService {
    public isRipe(mango: Mango) {
        return mango.ripeness === 'ripe';
    }
}
typescript

Now you can inject the MangoRipenessCheckerService into a controller.

@Controller()
export class DeliciousMangoController {
    @Inject()
    private readonly mangoRipenessCheckerService: MangoRipenessCheckerService;

    @On('check-mango-ripeness')
    public onCheckMangoRipeness() {
        const mango = new Mango();
        const isRipe = this.mangoRipenessCheckerService.isRipe(mango);
        console.log(`Is the mango ripe? ${isRipe}`);
    }
}
typescript

Providers

One of the ways to create a custom provider is to use the @Injectable decorator, which is used to mark a class as a provider.

There are four types of providers: useClass, useFactory, useValue, and useExisting. They are used in the @Module decorator to provide a class, factory, value, or existing provider as a provider.

Class-Based useClass

The useClass property is used to make a class available as a provider.

const deliciousMango = {
    provide: DeliciousMangoService,
    useClass: DeliciousMangoService,
};
typescript

Factory-Based useFactory

The useFactory property is used to provide a factory as a provider.

const deliciousMango = {
    provide: DeliciousMangoService,
    useFactory: (repository: DeliciousMangoRepository) => new DeliciousMangoService(repository),
    inject: [DeliciousMangoRepository],
};
typescript

Value-Based useValue

The useValue property is used to provide a value as a provider.

const deliciousMango = {
    provide: 'DELICIOUS_MANGO',
    useValue: {
        name: 'Delicious Mango',
        color: 'green',
    },
};
typescript

Existing-Based useExisting

The useExisting property is used to make an existing provider available as a provider.

const deliciousMango = {
    provide: 'MANGO_SERVICE',
    useExisting: DeliciousMangoService,
};
typescript

Scopes

The Mango Framework supports three scopes for providers: Singleton, Transient, and Request. The default scope is Singleton.

+
+
+
import { InjectableScope } from '@altv-mango/server'; 

const deliciousMango = {
    provide: DeliciousMangoService,
    useClass: DeliciousMangoService,
    scope: 'transient', 
    // OR
    scope: InjectableScope.Transient, 
};
typescript

Provider Registration

Providers are registered in the providers array of the module decorator options and can be exported to make them available to other modules.

TIP

You can specify the provider as an entire object in the providers array because the Mango Framework automatically takes the provide property as the identifier.

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+
@Module({
    providers: [deliciousMango], 
    exports: [deliciousMango], // Expose the provider to other modules that import this module  
})
export class DeliciousMangoModule {}
typescript

Dependency Injection

Mango Framework uses InversifyJS under the hood to provide dependency injection. Mango Framework provides a set of decorators to make

InversifyJS
easier to use.

Property-Based

The @Inject decorator is used to inject a dependency into a class.

+
+
@Controller()
export class DeliciousMangoController {
    @Inject(DeliciousMangoService) 
    private readonly deliciousMangoService: DeliciousMangoService; 
}
typescript
TIP

If you are injecting a class, you can use @Inject without any arguments. For example, @Inject() private readonly deliciousMangoService: DeliciousMangoService. This is because the class reference is used as the identifier. However, if your property type is string, number, or symbol, you must provide the identifier.

Optional

The @Optional decorator is used to inject a dependency into a class, but does not throw an error if the dependency is not found.

+
@Controller()
export class DeliciousMangoController {
    @Optional() 
    @Inject(DeliciousMangoService)
    private readonly deliciousMangoService: DeliciousMangoService;
}
typescript

Manual Provider Instantiation

You can manually instantiate a provider by injecting the MODULE_CONTAINER token into a class and using the Container to get the provider.

import type { Container } from 'inversify'; 

@Controller()
export class DeliciousMangoController {
    @Inject(MODULE_CONTAINER) private readonly container: Container; 

    @On('checkMangoRipeness')
    public onCheckMangoRipeness() {
        const deliciousMangoService = this.moduleContainer.get(DeliciousMangoService); 
        const mango = new Mango();
        const isRipe = deliciousMangoService.isRipe(mango);
        console.log(`Is the mango ripe? ${isRipe}`);
    }
}
typescript
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Last update at: 2024/04/29 10:15:50