Angular 4 remove required validator conditionally

Question

In Angular 4 app I have a form model like this:

this.form = this._fb.group({
    title: [\'\', [Validators.required, Validators.minLength(3), Validators.maxLengt         


        

Answer 1

I don't like clearing and setting validators, as I have to repeat all static validators (patterns, min, max, etc.) just to have a dynamic "required" validator.

I use a conditional validator:

export function conditionalValidator(condFn: (control: AbstractControl) => boolean,
validators: ValidatorFn | ValidatorFn[]): ValidatorFn {
  return (control) => {
    if (!condFn(control)) {
      return null;
    }

    if (!Array.isArray(validators)) {
      return validators(control);
    }

    return validators.map(v => v(control)).reduce((errors, result) =>
      result === null ? errors :
        (Object.assign(errors || {}, result))
    );
  };
}

I can then mix a static validator with a dynamic "required" condition:

this.fb.group({name: ['', [Validators.minLength(4),
                 conditionalValidator(this.isClientProj, Validators.required)]]}

Where isClientProj() is the condition function (closure)