Esta dando este erro quando ponho a linha
<span *ngIf="titulo.invalid" class="form-control alert-danger">
Título obrigatório
</span>O que pode ser ?
Erro:
zone.js:346 Error: Uncaught (in promise): Error: Error in http://localhost:3000/app/cadastro/cadastro.component.html:10:14 caused by: Cannot read property 'invalid' of undefined
at resolvePromise (zone.js:418)
at zone.js:395
at ZoneDelegate.invoke (zone.js:192)
at Object.onInvoke (core.umd.js:6242)
at ZoneDelegate.invoke (zone.js:191)
at Zone.run (zone.js:85)
at zone.js:451
at ZoneDelegate.invokeTask (zone.js:225)
at Object.onInvokeTask (core.umd.js:6233)
at ZoneDelegate.invokeTask (zone.js:224)
