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Re: [angular.js] Re: ngModelController Questions

Pete Bacon Darwin Jul 17, 2012 5:12 AM
Posted in group: Angular and AngularJS discussion
This is how I understand it...
  • The $modelValue is the external API of the value of the ModelController. The bit that is exposed to the user of the directive - i.e. in controllers.  The user can get and set the model values accordingly, usually by binding to the ng:model directive.
  • The $viewValue is the internal API that is exposed to the directives. A directive that displays the widget works with the $viewValue.
    • Whenever the widget needs to be shown or the $viewValue has been updated the $render method is called.  By default this is a no-op function and directive developers should override it with their own logic.  In the case of the ui-date directive, it calls element.datepicker("setDate", controller.$viewValue) which updates the jQuery date picker widget with the new value.  (Note to self: I just realised that since the default is a no-op then I don't need to call the original $render.)
    • If the widget changes its value (say by a user interaction) then the directive needs to call $setViewValue with the new value.  This commonly has to be wrapped in $apply since the update is likely to have come from outside Angular.
  • The $parsers and $formatters are a transformation pipeline that converts the $viewValue to the $viewModel and back again.  Each is an array of functions that take a value and return a value.
    • Whenever the $modelValue changes, all the $formatters are called to transform the $modeValue into the $viewValue.
    • Whenever the $viewValue changes, all the $parsers are called to transform the $viewValue into the $modelValue.
  • Any directive on an element can hook into this pipeline and affect the transformation between the $viewValue and the $modelValue.  They can also set the validity of the value in the FormController at this stage too.  This is how things like the required directive work.
I hope that is correct and helps.

On 17 July 2012 07:26, ProLoser <> wrote:
Does anyone have examples of using perhaps $parsers and $formatters to maintain 2 parallel values when changes are made, both programmatically in Angular and by events outside of angular?

On Monday, July 16, 2012 7:08:10 PM UTC-7, ProLoser wrote:
Why use ngModelController.$render instead of scope.$watch(iAttrs.ngModel)?
Is there a difference or significant reason for using one over the other?

How do I set / manage the model value? Lets say my model should be a rich object, but the view (<input>) should just have a string, my plugin already updates the text of view (<input>) but I don't know the best way to go about updating the model value. It doesn't make sense to watch the viewValue for change, because then I'd just be watching the model.

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