Angular2 - Module Separation - Best Practice

问题:

I have some Angular 2 services that have identical methods for parsing the json response, handling errors etc (eg. trapping if it's a 422 error for example).

Obviously I don't want these methods copy and pasted into each service, but I cannot seem to find any guidance on where I should put this code.

They are not class methods, just currently identical private methods in each service.

Here's one for example:

   private parseToString(jsonResponse: any){
    return Object.keys(jsonResponse).reduce(
      (prev, next) => prev.concat(jsonResponse[next].map(
        v => next + ' ' + v).join(', ')), []).join(', ');
  }  

Is there some way to create a helper module or something like a Rails Concern that you can include?

Say for example I have this folder:

app/services

which has my various .ts service files.

I could create "app/services/helpers" folder and put a file inside that...but what goes into that .ts file?

eg. parser-helper.ts could be the file name, but what does the code inside that look like? Should it be a module? If so, how can I include it into the service?

For example, is this the recommended way to do it?

app/services/helpers/parser-helper.module.ts

module parserHelperModule {

  export function helperA(){}
  export function helperB(){}

}

回答1:

You can have the common code as a common service itself as below

export class CommonService {
    public parseToString(jsonResponse: any){
            return Object.keys(jsonResponse).reduce(
                        (prev, next) => prev.concat(jsonResponse[next].map(
                            v => next + ' ' + v).join(', ')), []).join(', ');
  }  
   public someOtherMethod(){

   }
}

So you can import the class anywhere accross the application and use them

Note: When you are defining common methods in to a single service, make sure they are public

Update 1 :

Yes it is a good practice to use a separate module that serves all the common codes and making the main AppModule to import the CommonModule which would look like.

@NgModule({
  imports:    [ 
                HttpModule, Logger, Toaster, ... 
              ],
  declarations: [ CommonCmoponents
                ],
  providers:[Service1, Service2 ]
})
export class CommonModule { }

Make sure that your common module just serves as a collection, this CommonModule should not contain

1. Browser Module
2. Bootstrapping Components

You might be look for a the below image to have separation of concerns

回答2:

In parser-helper.ts:

export function parseToString(jsonResponse: any): string {
    ...
}

In any other TypeScript file:

import { parseToString } from './relative/path/to/parser-helper';

...
const s = parseToString(response);