CODEWITHSUNDEEP
nestjs
Horrendo
Horrendo

Reputation: 509

Access the collection of providers for a module in nestjs

Is there any way for a method in a class decorated with @Module() to iterate over all provider objects defined for that module?

Upvotes: 2

Views: 5006

Answers (2)

stefanitsky
stefanitsky

Reputation: 483

You can access metadata by a key and module class.

For example:

console.log(Reflect.getMetadata('providers', UserModule));

Output will be like:

[class UserService], [class ConfigService] ]

Underhood, @Module decorator looks like this:

function Module(metadata) {
    const propsKeys = Object.keys(metadata);
    validate_module_keys_util_1.validateModuleKeys(propsKeys);
    return (target) => {
        for (const property in metadata) {
            if (metadata.hasOwnProperty(property)) {
                Reflect.defineMetadata(property, metadata[property], target);
            }
        }
    };
}

It defines a metadata by a property key (providers, controllers, imports and etc.) and saves it for a target (module class).

Metadata API: https://github.com/rbuckton/reflect-metadata#api

Upvotes: 3

Horrendo
Horrendo

Reputation: 509

This might not be the best solution, but at least it 'works for me'. I ended up defining all the provider classes in an array:

const MyProviders = [ ProviderClass1, ProviderClass2, ...];

Then used that constant in the module definition:

@Module({
    imports: [],
    providers: MyProviders,
    exports: MyProviders,
    controllers: []
})
export class MyModule {

I defined the constructor to include a ModuleRef:

    public constructor(private readonly moduleRef: ModuleRef) {}

And then it was a relatively simple method to iterate over the instantiated provider objects:

    public someMethod(): void {
        for (const cls of MyProviders) {
            const provider = this.moduleRef.get(cls.name);
            //
            // Can now call methods, etc on provider
            //
        }
    }

If there's a better way of doing this, I'd love to hear it.

Upvotes: 1

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