forms - How to add [disabled]='!f.valid' to submit button using ng-content in angular 4? -


have form component contains email, password field , submit button passed through ng-content login form 'login' button can showed , register form 'register' button can showed. form component template code:

<form #f="ngform" (ngsubmit)="onsubmit(f.value)">    <div class="form-group">      <label for="email">email</label>      <input type="email"       class="form-control"       placeholder="enter email address"      name="email"      ngmodel      >   </div>    <div class="form-group">        <label for="password">password</label>        <input type="password"         class="form-control"         placeholder="enter password"        name="password"        ngmodel        >   </div>     <ng-content select="[submitbtn]" ></ng-content>

code of form's parent component:

  <div class="row">           <div class="col-md-6">             <!--for login-->             <app-form-content>          <button type="submit" class="btn btn-default" submitbtn>login</button>             </app-form-content>           </div>            <!--for register-->           <div class="col-md-6">              <app-form-content>                <button type="submit" class="btn btn-default" [disabled]="!f.valid" submitbtn>register</button>              </app-form-content>           </div>       </div>

after run code "typeerror: cannot read property 'valid' of undefined" error occured. how resolve error?

you can't use template reference variable #f in parent template because scope entire template declared.

in order access variable within parent template suggest declare property inside form component:

@viewchild('f') f: ngform;

after can property parent template reference #formcontent in parent template like:

<app-form-content #formcontent>    <button type="submit" class="btn btn-default" [disabled]="!formcontent.f.valid"

stackblitz example


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