Angular Directive: How to check if a scope function is defined?

Question

I know you can have optional property using a question mark like x:"=?" and then you can check if it is specified by checking if x is undefined or null.

How can I do similar thing for a function? Oftentimes, I want to hide a control if the function is not specified. I have to define another property for this purpose to workaround this problem. I wonder if there is a way to save this extra property.

Possible duplicate of How to check if a method argument of a directive is specified in AngularJS? — fracz
– fracz, Commented Jun 14, 2016 at 16:30

Community · Accepted Answer · 2017-05-23 12:16:00Z

2

I found an answer to this question at here. Here is a recap in case somebody is interested:

In directive:

scope: {
    callback: '&'
},
link: function(scope, elem, attrs) {    
  scope.hasCallback = function() {
    return angular.isDefined(attrs.callback);
  }
}

In html:

<a href="" ng-show="hasCallback()" ng-click="callback()">Call me back</a>

I like it very much because it saves me an extra parameter.

edited May 23, 2017 at 12:16

CommunityBot

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answered Jul 27, 2014 at 3:24

newman

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