javascript - Angular Reactive Forms: Dynamic Select dropdown value not binding -


i have 2 arrays of data: associatedprincipals (previously saved data) , referenceprincipals (static data populate in dropdown controls). i'm struggling previous value associatedprincipals displayed/selected in dynamic amount (most examples use single dropdown) of dropdowns on page load.

i'm not how set form (code behind , html), setting select's formcontrolname. currently, static values in each dropdown populate, cannot selected value bind properly.

public ngoninit() {     this.factsform = this.formbuilder.group({         associatedprincipals: this.formbuilder.array([]),         referenceprincipals: this.formbuilder.array([])     });      // data both of these methods comes external source...     var responsedata = // http source...     // push retrieved data form     this.initprincipals(responsedata[0]);     // push static data form    this.initstaticdata(responsedata[1]); }  public initprincipals(principals?: iassociatedprincipal[]): formarray {     principals.foreach((principal) => {  this.associatedprincipals.push(this.createprincipalformgroup(principal));     }); }  public initstaticdata(response: ireferenceprincipal[]) {    response.foreach((principal) => {       this.referenceprincipals.push(            this.formbuilder.control({                 code: principal.code,                 canhavelead: principal.canhavelead,                 isduplicate: false               }));         }); }  public createprincipalformgroup(principal: iassociatedprincipal) {         return this.formbuilder.group({             code: principal.code,             canhavelead: false,             isduplicate: false         });     }  public associatedprincipals(): formarray {         return this.factsform.get('associatedprincipals') formarray;     }      public referenceprincipals(): formarray {         return this.factsform.get("referenceprincipals") formarray;     }

html:

 <form novalidate [formgroup]="factsform">         <div formarrayname="associatedprincipals">              <div *ngfor="let associatedprincipal of associatedprincipals.controls; let i=index;" [formgroupname]="i" >                 <select class="form-control create-input"                         formcontrolname="i">                      <option value=null disabled selected hidden>--select--</option>                        <option *ngfor="let refprincipal of referenceprincipals.controls" [ngvalue]="refprincipal">refprincipal.value.code</option>                  </select>              </div>          </div>     </form>

i appreciate feedback!

edit: added plunker showing issue: https://embed.plnkr.co/xmlvfubuc32estlyldgo/

problems in demo

based on demo provided, there several problems listed below:

  • there no formcontrolname assigned select.
  • you binding object select's option.

for first problem

since looping through associatedprincipals show dropdownlist dynamically. , associatedprincipals formarray can consider below:

associatedprincipals = {   "0": formcontrol,   "1": formcontrol }

so can assign i defined @ *ngfor expression formcontrolname.

<select formcontrolname="{{i}}" style="margin-top: 10px">    ... </select>

for second problem

while binding object option, angular compare default value , option's value object instance default.

you can set same instance(get value of referenceprincipals's formcontrols) formcontrol of associatedprincipals(as @fetra r.'s answer). not convenient way since have take logic keep same instance of object.

here give solution using comparewith directive designed current situation, see docs.

using comparewith directive, need implement comparefun tell angular how consider 2 objects(with different instances) same.here yo can include comparing object instance , comparing object fields @ same time.

<select formcontrolname="{{i}}" style="margin-top: 10px" [comparewith]="comparefun">   <option value=null disabled selected hidden>--select--</option>   <option *ngfor="let refprincipal of referenceprincipals.controls"      [ngvalue]="refprincipal.value">{{ refprincipal.value.code }}</option> </select>  // tell angular how compare 2 objects comparefn(item1, item2): boolean {   return item1 && item2 ? item1.code === item2.code : item1 === item2; }

refer docs , fixed demo learn detail it.


Comments

Post a Comment

Popular posts from this blog

angular - Ionic slides - dynamically add slides before and after -

hi i'm using ngfor create set of 3 slides while starting in middle i'm guaranteed able slide left or right on start. when slide right can simple listen reachedend , push slide array i'm looping. but have problem adding slide beginning. if same above , use e.g. array.unshift() or spread add item beginning, view think it's on position 0 , snaps view new slide. the code below work animates slide change index 1. slide = [0,1,2] //example loop slidechanged(event) { if(this.slides.isbeginning()){ this.slide = [this.slide[0]-1, ...this.slide]; this.slides.update(); this.slides.slideto(1) } } <ion-slides [initialslide]="1" (ionslidedidchange)="slidechanged($event)"> <ion-slide *ngfor="let item of slide"> <h1>slide {{item}}</h1> </ion-slide> </ion-slides> any appreciated! you can using ionslidenextend , ionslideprevend events slides . please...
Read more

Add a dynamic header in angular 2 http provider -

i have http interceptor built via tutorial https://scotch.io/@kashyapmukkamala/using-http-interceptor-with-angular2 the problem need have dynamic header changes automatically once changes 'mode' in app. service able tell interceptor change header, or have interceptor pull header (which string)from service each request. able throwing away patch method, call http.patch('new header string') set header string. call in service controls 'mode' setting. wondering if there way interceptor pull recent value service each request or if can add method http provider via interceptor? i've tried call service in interceptor each request returns undefined. because creating new instance of service or copying value before service fired , loaded/changed data. i don't want pass header string every http provider call because defeats purpose of having interceptor, id able set once changes or have provider fetch service before makes request. tl;dr : need add autom...
Read more

minify - Minimizing css files -

i want know how css files can minimized. currently, using external sites css minifier compress css files. however, after removing whitespaces, comments, etc, file sizes reduced 10-15%. how frameworks bootstrap manage make minimized versions kilobytes. as example, css is: body { background-color: #ff0; } the reduction goes 28 bytes 22 bytes other css files have lot more characters still smaller this. actually minifying code means it's remove thing code white space characters new line characters comments block delimiters it reduces amount of code has transferred on web , speed site load fastly.but unreadable format.
Read more