CODEWITHSUNDEEP
angulartypescriptangular2-aot
antoine
antoine

Reputation: 103

Angular provider not provided in AOT

I would like to make facilitate the declaration of a provider by calling a static function like this : 

const provider = MyModule.makeProvider();

@NgModule({
  bootstrap: [AppComponent],
  declarations: [AppComponent],
  imports: [
     ...
  ],
  providers: [
    provider,
    ...
  ],
})

but it fails with AOT (the provider is missing)

Whereas this is working :

const providers = [{provide : myToken, useValue: "value"}];

@NgModule({
  bootstrap: [AppComponent],
  declarations: [AppComponent],
  imports: [
     ...
  ],
  providers: [
    provider,
    ...
  ],
})

Upvotes: 2

Views: 449

Answers (2)

antoine
antoine

Reputation: 103

As workaround I added a static function to my module. This function returns a ModuleWithProviders as follow :

import { NgModule, ModuleWithProviders } from '@angular/core';

// ....

public static withValue(value: string): ModuleWithProviders {
  return {
    ngModule: MyModule,
    providers: [
      { provide: MY_TOKEN, useValue: value},
    ],
};

Upvotes: 1

Armen Vardanyan
Armen Vardanyan

Reputation: 3315

Yes, this is because anything a module declares/uses should be statically analyzable for AOT to work. See this for further information

What do we understand by statically analyzable? It means another program does not have to run a function to understand what a certain value may be, as it can be inferred from the code itself. You cannot infer any return value from a function because of the famous Halting Problem

As you run a function to get the providers, AOT compiler will be confused. This also refers to dynamic templates/css style declarations

Upvotes: 1

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