Angular2 by default will check for the form control/form group validity cascadingly up to the top level whenever there’s an update to any form element value, unless you say no. onlySelf
is the tool to help you do that.
Say you have a loginForm
that has a username
field and a password
field, both of them are required, like this:
this.userNameControl = this.formBuilder.control('Harry', Validators.required);
this.passwordControl = this.formBuilder.control('S3cReT', Validators.required);
this.loginForm = this.formBuilder.group({
userName: this.userNameControl,
password: this.passwordControl
});
After this code, this.loginForm.valid
is true
.
If you set the value of a control using the default setting (onlySelf = false
), Angular2 will update the control’s validity as well as form group’s validity. For example, this:
this.passwordControl.setValue('');
will result in
this.passwordControl.valid === false
this.loginForm.valid === false
However, this:
this.passwordControl.setValue('', { onlySelf: true });
will only change passwordControl
‘s validity only:
this.passwordControl.valid === false
this.loginForm.valid === true