angular - Correct use of Elvis operator in Angular2 for Dart component's view

Question

I see in Angular2 Dart Angular for Dart Cheat Sheet (v2.0.0-beta.2) that the Elvis operator is supported.

I am trying to use it in an a components view but it seems that it is not allowed here.

Given

.html

  <div
    <label
        for = "first">First<span class = "require">*</span></label>
    <input
        type = "text"
        [(ngModel)] = "name?.first"
        id = "first">

.dart

...
Name name = new Name();
...

Running the application gives the following error:

error trace

Transform TemplateCompiler on 
epimss_ng2_reg|lib/components/name_component.ng_meta.json threw error: Template parse errors:
Parser Error: The '?.' operator cannot be used in the assignment at column 13 in [name?.first=$event] in NameComponent@39:12 ("
        <input
            type = "text"
            [ERROR ->][(ngModel)] = "name?.first"
            #firstCtrl = "ngForm"
            [ngFormControl] = "nameForm"): NameComponent@39:12

What circumstance can I use the operator in a component's view?

Cheers

Answer 1

As the error message says it can't be used for assignment. Where should the value be assigned to when name is null? If you split the short form to the more explicit one

[ngModel]="name?.first" (ngModelChange)="name.first=$event"

then you can use the elvis operator.