Angular2仅在某些条件下验证表单

Question

I would like to vlidate a user form only during create but not update

This is my validation logic

    this.userform = this._formbuilder.group({
  first_name: ['', Validators.required],
  last_name: ['', Validators.required],
  username: ['', Validators.compose(
    [
      Validators.required,Validators.minLength(5)
    ]
  )],
  password: ['',Validators.compose([
    Validators.required,ValidationService.passwordValidator
  ])],
  email: ['', Validators.compose([
    Validators.required,ValidationService.emailValidator
  ])],
  role: ['', Validators.required],

})

I would like to validate the password only during create that is when the newuser variable is true so ive tried

    this.userform = this._formbuilder.group({
  .....

  password: ['',

       (this.newUser) ?Validators.compose([
          Validators.required,ValidationService.passwordValidator
          ]):"" 

       ],
....
})

The above fails an returns an error

rror: Error in ./UsersComponent class UsersComponent - inline  
    template:113:51 caused by: 
   v is not a function
   Error: Error in ./UsersComponent class UsersComponent -
     inline template:113:51 caused by: v is not a function

Answer 1

You can create a custom validator where you programmatically check for required and call passwordValidator if this.user is available set it as the only validator.

Or

You could initially set:

  this.userform = this._formbuilder.group({
  .....

  password: [''] //no initial validators,
....
})

and in the function where this.newUser is set to true ,use setControl

this.userform.setControl("password",new FormControl('',Validators.compose([
          Validators.required,ValidationService.passwordValidator
          ]));

Answer 2

Why you don't want to validate the form when a user what to change his profile? That means that a user can, after an update of his profile, have no username, no password and no email? It's not logic.