title: Angular FormBuilder multiple FormGroups
body: <p>I have a form with 2 FromGroups (User &amp; Address)</p>
  
  <p>I get the following error:</p>
  
  <pre><code> core.es5.js:1084 ERROR Error: Uncaught (in promise): Error: Cannot find control with name: 'street'
  </code></pre>
  
  <p>when I use this class</p>
  
  <pre><code>export class FormBuilderComp {
          addUserFrom: FormGroup;
          constructor( @Inject(FormBuilder) fb: FormBuilder) {
              this.addUserFrom = fb.group({
                  userGroup: fb.group({
                      name: ['', Validators.required],
                      email: ['', Validators.required],
                      phone: ['', Validators.required]
                  }),
                  addressGroup: fb.group({
                      street: ['', Validators.required],
                      suite: ['', Validators.required],
                      city: ['', Validators.required],
                      zipCode: ['', Validators.required]
                  })
              });
          }
      }
  </code></pre>
  
  <p>...But if I take out one of the nested FormGroups as in</p>
  
  <pre><code>  export class FormBuilderComp {
          addUserFrom: FormGroup;
          constructor( @Inject(FormBuilder) fb: FormBuilder) {
              this.addUserFrom = fb.group({
                  userGroup: fb.group({
                      name: ['', Validators.required],
                      email: ['', Validators.required],
                      phone: ['', Validators.required]
                  }),
                  street: ['', Validators.required],
                  suite: ['', Validators.required],
                  city: ['', Validators.required],
                  zipCode: ['', Validators.required]
  
              });
          }
      }
  </code></pre>
  
  <p>The error disappears.</p>
  
  <p>Is there some rule about not having more than one nested FromGroup??</p>
  
  <p>Here's the html in case it's relevant </p>
  
  <pre><code> &lt;form [formGroup]="addUserFrom"&gt;
          &lt;fieldset formGroupName="userGroup"&gt;
                  &lt;legend&gt;User&lt;/legend&gt;
              &lt;div class="form-group"&gt;
                  &lt;label for="name"&gt;Name&lt;/label&gt;
                  &lt;input 
                      type="text" 
                      class="form-control" 
                      id="name" 
                      formControlName="name"&gt;
              &lt;/div&gt;
              &lt;div class="form-group"&gt;
                  &lt;label for="email"&gt;Email&lt;/label&gt;
                  &lt;input 
                      type="text" 
                      class="form-control" 
                      id="email" 
                      formControlName="email"&gt;
              &lt;/div&gt;
              &lt;div class="form-group"&gt;
                  &lt;label for="phone"&gt;Phone&lt;/label&gt;
                  &lt;input 
                      type="text" 
                      class="form-control" 
                      id="phone" 
                      formControlName="phone"&gt;
              &lt;/div&gt;
          &lt;/fieldset&gt;
          &lt;fieldset fromGroupName="addressGroup"&gt;
              &lt;legend&gt;Address&lt;/legend&gt;
          &lt;div class="form-group"&gt;
                  &lt;label for="street"&gt;Street&lt;/label&gt;
                  &lt;input 
                      type="text" 
                      class="form-control" 
                      id="street" 
                      formControlName="street"&gt;
              &lt;/div&gt;
              &lt;div class="form-group"&gt;
                  &lt;label for="suite"&gt;Suite&lt;/label&gt;
                  &lt;input 
                      type="text" 
                      class="form-control" 
                      id="suite" 
                      formControlName="suite"&gt;
              &lt;/div&gt;
              &lt;div class="form-group"&gt;
                  &lt;label for="city"&gt;City&lt;/label&gt;
                  &lt;input 
                      type="text" 
                      class="form-control" 
                      id="city" 
                      formControlName="city"&gt;
              &lt;/div&gt;
              &lt;div class="form-group"&gt;
                  &lt;label for="zipCode"&gt;Zip Code&lt;/label&gt;
                  &lt;input 
                      type="text" 
                      class="form-control" 
                      id="zipCode" 
                      formControlName="zipCode"&gt;
              &lt;/div&gt;
          &lt;/fieldset&gt;
  
          &lt;button&gt;Submit&lt;/button&gt;
      &lt;/form&gt;
  </code></pre>