How to set value to form control in Reactive Forms in Angular

Question

Hi Everyone I m new to angular  Actually  I m trying to subscribe data from a service and that data  I m passing to form control of mine from  example  it s like an edit form    import   Component  OnInit   from   angular core   import   FormBuilder  FormGroup  Validators  FormArray  FormControl   from   angular forms   import   ActivatedRoute  Router   from   angular router   import   QuestionService   from     shared question service     Component     selector   app-update-que     templateUrl     update-que component html     styleUrls      update-que component scss      export class UpdateQueComponent implements OnInit      questionsTypes     Text Type    Multiple choice    Single Select      selectedQuestionType  string         question  any          constructor private route  ActivatedRoute  private router  Router      private qService  QuestionService  private fb  FormBuilder             ngOnInit           this getQuebyid           getQuebyid        this route params subscribe params   gt          this qService editQue  params  id     subscribe res   gt           this question   res                           editqueForm    this fb group       user            questioning       Validators required       questionType       Validators required       options  new FormArray             setValue        this editqueForm setValue  user  this question user  questioning  this question questioning            if I use   ngModule   on my form field to set the value to my element it is working fine and showing a warning it ll be deprecated in angular 7 version    lt textarea formControlName  questioning    ngModule    question questioning  cols  70  rows  4  gt  lt  textarea gt    So  I set the values to my form control by doing below but the element is not showing those values   setValue       this editqueForm setValue  user  this question user  questioning  this question questioning       can anyone tell me how to set values to mine reactive form  Please suggest me

User · Answer

The  usual  solution is make a function that return an empty formGroup or a fullfilled formGroup  createFormGroup data any     return this fb group      user   data data user null      questioning   data data questioning null  Validators required      questionType   data data questionType  Validators required      options  new FormArray  this createArray data data options null           return an array of formGroup createArray data any   null  FormGroup        return data map x  gt this fb group                          then  in SUBSCRIBE  you call the function  this qService editQue  params  id     subscribe res   gt      this editqueForm   this createFormGroup res         be carefull   your form must include an  ngIf to avoid initial error   lt form  ngIf  editqueForm   formGroup   editqueForm  gt           lt  form gt

User · Answer

To assign value to a single Form control individually  I propose to use setValue in the following way   this editqueForm get  user   setValue this question user    this editqueForm get  questioning   setValue this question questioning

User · Answer

Use patchValue   method which helps to update even subset of controls   setValue      this editqueForm patchValue  user  this question user  questioning  this question questioning        From Angular docs setValue   method      Error When strict checks fail  such as setting the value of a control that doesn t exist or if you excluding the value of a control    In your case  object missing options and questionType control value so setValue   will fail to update

User · Answer

Setting or Updating of Reactive Forms Form Control values can be done using both patchValue and setValue  However  it might be better to use patchValue in some instances    patchValue does not require all controls to be specified within the parameters in order to update set the value of your Form Controls  On the other hand  setValue requires all Form Control values to be filled in  and it will return an error if any of your controls are not specified within the parameter   In this scenario  we will want to use patchValue  since we are only updating user and questioning   this qService editQue  params  id     subscribe res   gt      this question   res    this editqueForm patchValue       user  this question user      questioning  this question questioning             EDIT  If you feel like doing some of ES6 s Object Destructuring  you may be interested to do this instead    const   user  questioning     this question   this editqueForm patchValue     user    questioning       Ta-dah

User · Answer

In Reactive Form  there are 2 primary solutions to update value s  of form field s    setValue    Initialize Model Structure in Constructor   this newForm   this formBuilder group        firstName        Validators required  Validators minLength 3   Validators maxLength 8        lastName        Validators required  Validators minLength 3   Validators maxLength 8         If you want to update all fields of form   this newForm setValue      firstName   abc      lastName   def       If you want to update specific field of form   this newForm controls firstName setValue  abc       Note  It   s mandatory to provide complete model structure for all form field controls within the FormGroup  If you miss any property or subset collections  then it will throw an exception   patchValue    If you want to update some  specific fields of form   this newForm patchValue      firstName   abc         Note  It   s not mandatory to provide model structure for all  any form field controls within the FormGroup  If you miss any property or subset collections  then it will not throw any exception

User · Answer

Try this  editqueForm    this fb group      user   this question user      questioning   this question questioning  Validators required      questionType   this question questionType  Validators required      options  new FormArray         setValue   and patchValue   if you want to set the value of one control  this will not work  therefor you have to set the value of both controls  formgroup setValue  name     abc     age     25        It is necessary to mention all the controls inside the method  If this is not done  it will throw an error  On the other hand patchvalue   is a lot easier on that part  let   s say you only want to assign the name as a new value  formgroup patchValue  name    abc

[angular] How to set value to form control in Reactive Forms in Angular

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