Access a service from a custom validator in Angular2

Question

I need to access my custom http service from inside a static method, as example:

import {Control} from 'angular2/common';
import {HttpService} from './http.service';

class UsernameValidator {
    static usernameExist(control: Control): Promise<ValidationResult> { 
        ... /* Access my HTTPservice here */
    }
}

How can I access a service in this case?

Answer 1

Another approach consists in returning a function. This way this function can have access to HttpService instance provided during creation:

class UsernameValidator {
  static createUsernameExist(http:HttpService) {
    return (control: Control) => { 
      ... /* Access my HTTPservice here */
    }
  }
}

You can then use it like that:

validator: UsernameValidator.createUsernameExist(this.httpService)

Answer 2

class UsernameValidator {
    constructor(http:HttpService){}

    usernameExist(control: Control): Promise<ValidationResult> { 
        ... /* Access my HTTPservice here */
    }
}

then use it like

validator: new UsernameValidator(http).usernameExist

The HttpService needs to be injected in the component constructor instead and then passed to the manually created validator instance as shown above.