I tried to put together a more in-depth demo what I am trying to do:
http://bjam.in/ng2-fail-ng-model
It works with the setTimeout(), but is very clearly sub-optimal. Any help
is much appreciated. Super frustrating.
On Sunday, January 31, 2016 at 7:16:05 AM UTC-5, Ben Nadel wrote:
>
> Looking through all the existing valueAccessors examples in the AngularJS
> source code doesn't help because all of them simply update existing DOM
> elements. As such, the writeValue() method never updates anything that is
> part of dirty-checking.
>
> I need to update the value of an AngularJS component, based on the
> writeValue().
>
>
>
> On Sunday, January 31, 2016 at 6:54:54 AM UTC-5, Ben Nadel wrote:
>>
>> I am trying to understand how to create custom valueAccessor
>> implementations to bind [ngModel] to an existing Widget directive in order
>> to give it two-way data binding. So, imagine that I have:
>>
>> Widget
>> inputs: [ "value" ] ---> Sets the selected value of the widget.
>> outputs: [ "select" ] ---> Emits event when value *should be selected*
>> (ie, doesn't change it internally).
>>
>> Ok, now I'm trying to create a valueAccessor that selects on
>> "widget[ngModel]"... such that
>>
>> <widget [(ngModel)]="someValue" />
>>
>> ... will match TWO directives - the "Widget component" (which knows
>> nothing about ngModel) and the "accessor directive."
>>
>> So far so good. Until I implement the *writeValue()* method:
>>
>> function writeValue( newValue ) {
>> widget.value = newValue;
>> }
>>
>> Here, Angular is throwing the error:
>>
>> Expression 'value in AppController@4:8' has changed after it was checked.
>> Previous value: 'false'. Current value: 'true' in [value in
>> AppController@4:8]
>>
>> If I wrap the "widget.value = newValue;" in a setTimeout(), the error
>> goes away. But, I don't believe this is a *fix*. I think I am just missing
>> something fundamental about change detection. Or valueAccessors.
>>
>> It almost as if the fact that both directives match on the same Node, one
>> directive cannot alter the other's inputs. But, as they are different
>> directives,
>>
>> Thanks!
>>
>
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