How to trigger Form Validators in Angular2

Question

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!

Answer 1

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!

EDIT: Updated link and example. Code changed while I was writing my answer.

EDIT_2: alpha.48 changes the EventEmitter.observer to EventEmitter.subscribe!

EDIT_3: Changed link to the actual implementation, added link to the documents

Validaton-Guide

FormControl Documentation