How to trigger Form Validators in Angular2 - forms

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.
Validaton-Guide
FormControl Documentation

Answer 2

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)

Answer 3

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

Answer 4

This did the trick for me
this.myForm.markAllAsTouched();

Answer 5

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
});
}

Answer 6

You can trigger validation in this way:
this.myform.get('myfield').updateValueAndValidity();

Answer 7

static minMaxRange(min: number, max: number): ValidatorFn {
return (control: AbstractControl): ValidationErrors | null => {
if (Validators.min(min)(control)) { // if min not valid
return Validators.min(min)(control);
} else {
return Validators.max(max)(control);
}
};
}

Answer 8

Here is another similar way that also uses markAsDirty and updateValueAndValidity, particularly good if you use angular material where markAsTouched is not enough.
export function forceValidation(form: AbstractControl) {
if (form instanceof FormGroup || form instanceof FormArray) {
for (const inner in form.controls) {
const control = form.get(inner);
control && forceValidation(control);
}
} else {
form.markAsDirty();
form.markAsTouched();
form.updateValueAndValidity();
}
}