Can not inject config param in constructor

When I try to inject a param in the constructor of my class using the ConfigParam decorator on the function argument and the Configurable decorator in the function, as suggested by the docs, TypeScript is throwing an error on the Configurable decorator.

This is my code:

@Configurable()
public constructor(@ConfigParam('app.env') private readonly env: string) { }

And this is the error: TS1206: Decorators are not valid here.

I managed to make it work with this:

private readonly env: string;

public constructor(private readonly config: ConfigService) {
  this.env = config.get('app.env');
}

but that defeats completly the purpose of the decorators.

Am I doing something wrong?

[bashleigh]

I don’t think you can apply a method decorator on the constructor? We could develop a class decorator but this would also defeat the purpose as we’d override the constructor method to inject the ConfigService. Where are you using the configured variable?

It might be possible to use the static method on the ConfigService within your constructor.

export class Test {
  constructor() {
    this.property = ConfigService.get('app.env');
  }
}

Else I would use the Configurable decorator on the class’s methods where you would use the variable. Or another method would be to use a factory

import {Module} from '@nestjs/common';

@Module({
  imports: [ConfigModule],
  providers: [{
    useFactory: (config: ConfigService) => new Test(config.get('app.env')),
    inject: [ConfigService],
})
export class TestModule {}

Not really what you want though is it? But doesn’t inject into your provider.

[FahmyChaabane]

Hello from the future !!

I’m stuck at this. was there any workaround for this ?