How can i implement my custom validator on Angular 2?

Question

How can I implement my custom Validator in Angular 2?

I found this plunker:

constructor(private fb: FormBuilder) {
    this.form = fb.group({
        'singleSelection': ['Rio', [App.validateCity]] // initial value as string
        'multipleSelection': [['Red','Blue'], [App.validateColor]]  // initial value as array
    });
}

static validateCity(c: FormControl) {
    if (c.value !== 'New York') {
        return { citySucks: true };
    }
    return null;
}

static validateColor(c: FormControl) {
    if (c.value.indexOf('Green') < 0) {
        return {badColor: true};
    }
    return null;
}

But, I think it would be better to implement an interface Validator, like class MinLengthValidator. But, I don't know how to use it!

Answer 1

// Control handling

          this.form = fb.group({
            'singleSelection': ['Rio', this.text({min: 10})]
          });

// Text function to handle min value

           public static text(config = {}): ValidatorFn {
             return (control: Control): {} => {
                if(!control) {
                   return null;
                }

              let c: string = control.value;

            if(config.min) {
              if(c.length < config.min) {
                  return {
                  "This field must have at least " + config.min + " characters."
                  };
               }
             }
           }}