How to trigger Form Validators in Angular2

In angular2 I want to trigger Validators for some controls when a another control is changed. Is there some way that I can just tell the form to re-validate? Better still, can I request validation of specific fields?

Example: Given Checkbox X and input P. Input P has a validator that behaves differently based on the model value of X. When X is checked/unchecked I need to invoke the validator on P. The Validator on P will look at the model to determine the state of X and will validate P accordingly.

Here's some code:

constructor(builder: FormBuilder) {
    this.formData = { num: '', checkbox: false };

    this.formGp = builder.group({
        numberFld: [this.formData.num, myValidators.numericRange],
        checkboxFld: [this.formData.checkbox],
    });
}

this.formGp.controls['checkboxFld'].valueChanges.observer({
    next: (value) => {
        // I want to be able to do something like the following line:
        this.formGp.controls['numberFld'].validator(this.formGp.controls['numberFld']);
    }
});

Anybody have a solution? Thanks!

I don't know if you are still looking for an answer, so here is my suggestions:

Have a look at this: Angular 2 - AbstractControl

I think what you could do is following:

this.formGp.controls['checkboxFld'].valueChanges.observer({
    next: (value) => {
       this.formGp.controls['numberFld'].updateValueAndValidity();
    }
});

This should trigger and run the validators. Furthermore the state gets updated as well. Now you should be able to consult the checkbox value within your validator logic.

Hope this helps!

Validaton-Guide

FormControl Documentation

with my ControlGroup I do this because I have errors divs checking if touched

for (var i in this.form.controls) {
  this.form.controls[i].markAsTouched();
}

(this.form is my ControlGroup)

With the help of this blog

blog link

I have came across a solution with the combine of Nightking answer

Object.keys(this.orderForm.controls).forEach(field => {
       const control = this.orderForm.get(field);
       control.updateValueAndValidity();

});

this.orderForm is the form group

This did the trick for me

this.myForm.markAllAsTouched();

There are more elegant ways of modeling this behavior - for example, putting your state into a ReplaySubject and observing that, and then using async validators observing the state - but the pseudo-coded approach below should work. You simply observe the value changes in the checkbox, update the model as appropriate, then force a re-validation of the numberFld with the updateValueAndValidity cal.

constructor(builder: FormBuilder) {
  this.formData = { num: '', checkbox: false };
  const numberFld = builder.control(this.formData.num, myValidators.numericRange);

  const checkbox = builder.control(this.formData.checkbox);
  checkbox.valueChanges.map(mapToBoolean).subscribe((bool) => {
    this.formData.checked = bool;
    numberFld.updateValueAndValidity(); //triggers numberFld validation
  });

  this.formGp = builder.group({
      numberFld: numberFld,
      checkboxFld: checkbox
  });
}