Angular2 reactive form error display

Question

I am trying to learn about reactive forms of Angular2 by creating a contact form. Everything works well, but there is a bug that seems to give me some trouble. Everything works fine when I use Validators.required, but as soon as I add Validators.minLengthor anything else in one of the controls, all messed up, and I get this error in the browser console Expected validator to return Promise or Observable.. I looked around, but I could not find a simple explanation / Here is my component:

export class ContactRouteComponent {
contactForm: FormGroup;
reasons = REASONS;

constructor(private fb: FormBuilder) {
    this.createForm();
}

createForm() {
    this.contactForm = this.fb.group({
        name: ['', <any>Validators.required, <any>Validators.minLength(3)],
        email: ['', <any>Validators.required],
        reason: ['',<any>Validators.required],
        message: ['', <any>Validators.required]
    });

    // AFISEAZA MESAJE EROARE
    this.contactForm.valueChanges.subscribe(data => this.onValueChanged(data));
    this.onValueChanged();
}

onSubmit() {
    console.log(this.prepareContactForm());
    this.contactForm.reset();
}

prepareContactForm() {
    const formModel = this.contactForm.value;

    const contactValues: Contact = {
        name: formModel.name as string,
        email: formModel.email as string,
        reason: formModel.reason as string,
        message: formModel.message as string
    };

    return contactValues;
}

onValueChanged(data?: any) {
    if(!this.contactForm) { return; }
    const form = this.contactForm;

    for(const field in this.formErrors) {
        // clear previous messages
        this.formErrors[field] = '';
        const control = form.get(field);

        if(control && control.dirty && !control.valid) {
            const messages = this.validationMessages[field];
            for(const key in control.errors) {
                this.formErrors[field] += messages[key] + ' ';
            }
        }
    }
}

formErrors = {
    'name': '',
    'email': '',
    'reason': '',
    'message': ''
}

validationMessages = {
    'name': {
        'required': 'Name is required',
        'minLength': 'Name has to be...'
    },
    'email': {
        'required': 'Name is required'
    },
    'reason': {
        'required': 'Name is required'
    },
    'message': {
        'required': 'Name is required'
    }
}

}

Answer 1

If you have several validation rules, you should insert them inside the array as such:

this.fb.group({
      password: ['', [ Validators.required, Validators.minLength(5)] ]
    })

Update to Angular v5

Later implementation without FormBuilder:

form = new FormGroup({
  email: new FormControl('', 
    Validators.compose([ Validators.minLength(5), Validators.email ])),
});

Answer 2

, []

this.contactForm = this.fb.group({
    name: ['', 
       [Validators.required, Validators.minLength(3)]
    ],
    email: ['', Validators.required],
    reason: ['', Validators.required],
    message: ['', Validators.required]
});