Angular 4 remove required validator conditionally

问题:

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

this.form = this._fb.group({
    title: ['', [Validators.required, Validators.minLength(3), Validators.maxLength(50)]],
    description: ['', [Validators.required, Validators.minLength(3)]]
});

Now what I want is to remove dynamically only the required validator from the control validators array. Something like this:

saveDraft() {
    this.form.controls['title'].removeValidator('required'); //Just a fake implementation for demonstration
}

This question is not the duplicate of the mentioned question. My case is different I just want to remove the required validator unknowingly the other ones.

回答1:

if you want to add validation try this one.

saveDraft() {
   this.form.get('title').setValidators([Validators.required, Validators.minLength(3)]);
   this.form.get('title').updateValueAndValidity();
}

if you want to remove validators try this one.

saveDraft() {
 this.form.get('title').clearValidators();
 this.form.get('title').updateValueAndValidity();
}

回答2:

saveDraft() {
   this.form.get('title').setValidators([Validators.required, Validators.minLength(3)]);
   this.form.get('title').updateValueAndValidity();
}

saveDraft() {
 this.form.get('title').clearValidators();
 this.form.get('title').updateValueAndValidity();
}

回答3:

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)

回答4:

we can use setValidators to remove validation.

this.form.get('title').setValidators(null); 
this.form.get('title').setErrors(null); 

回答5:

Unfortunately Angular doesn't have a removeValidator capability at this point in time. All you can do is re-set the validators without the one you want to remove, so you need to know which validators you want to keep rather than which one you want to remove. so this:

this.form.get('title').setValidators([Validators.minLength(3), Validators.maxLength(50)]);

Is the closest you have to a remove function. You can't access the current validators on a formcontrol either to try and write your own remove function. The best you could do is write your own form control validation manager class that can keep track of the validators on a given control and manage them for you.

回答6:

I had the same problem with saving entry as draft and prepared the following solution:

@Component({
    // ...
})
export class FormComponent{
    form: FormGroup;

    constructor(private fb: FormBuilder){
        this.form = this.fb.group({
            name: ['', Validators.required, Validators.maxLength(20)],
            description: ['', Validators.required, Validators.maxLength(200)],
            address: this.fb.group({
                line1: ['', Validators.required, Validators.maxLength(100)],
                line2: ['', Validators.maxLength(100)]
            })
        });
    }    

    validateDraft(formElement: FormGroup | FormArray | FormControl): boolean {
        let result = true;

        Object.keys(formElement.controls).forEach(field => {
            const control = formElement.get(field);

            if(control instanceof FormControl) {
                control.markAsTouched({ onlySelf: true });

                if(control.errors && control.errors['required']) {
                    control.markAsUntouched({ onlySelf: true });
                }
                else if(control.invalid) {
                    result = false;
                }
            } else if (control instanceof FormArray) {
                if (!this.validateDraft(control)) {
                    result = false;
                } 
            }else if (control instanceof FormGroup) {
                if (!this.validateDraft(control)) {
                    result = false;
                }   
            }
        });
    }

    saveDraft(){
        if(this.validateDraft(this.form)){
            //save draft - ignore required errors
        }
    }

    save(){
        if(this.form.valid){
            //save
        }
    }
}

回答7:

To Add Validators:

this.form = this._fb.group({
    title: ['', [Validators.required, Validators.minLength(3), Validators.maxLength(50)]],
    description: ['', [Validators.required, Validators.minLength(3)]]
});

or

this.form.get('title').setValidators([Validators.required,Validators.minLength(3), Validators.maxLength(50)]);

To Remove the 'Required' validator only, you can reset the validators.

saveDraft() {
     this.form.get('title').setValidators([Validators.minLength(3), Validators.maxLength(50)]);
     this.form.get('title').updateValueAndValidity();
}

updateValueAndValidity determines how the control propagates changes and emits events when the value and validators are changed

回答8:

Use empty array to remove all existing validators.

this.frmFeasibility.controls['pop_name'].setValidators([]);
this.frmFeasibility.controls['pop_name'].updateValueAndValidity();