Passing variable to directive's attribute

Question

In AngularJS, how can I use a variable within an attribute of a directive?

Without any directives, this work fine:

<a 
    href="#/fruits/{{ fruit.short }}/details" 
    title="Back to Fruit details">
    Back
</a>

Now with directive, this does not work:

<backButton 
    href="#/fruits/{{ fruit.short }}/details" 
    title="Fruit details">
</backButton>


MyApp.directive( 'backbutton', function() 
{
    return {
        restrict: 'E',
        link: function( scope, element, attrs ) 
        {
            var href    = attrs.href;
            var title   = attrs.title;

            console.log( "href = " + href );    // undefined
            console.log( "title = " + title );  // Fruit details

            element.html('<a href="' + href + '" title="Back to ' + title + '">Back</a>');
        }
    };
});

The directive itself works fine for e.g. href="#/fruits/novariableused". But as soon as I use a variable in the href attribute, its value becomes undefined.

How can I fix this ?

Solution

Angular will interpolate your href attribute after the linking process, however you can observe the attrs. It's in the docs: Directive Attributes

attrs.$observe('href', function ( value ) {
    // here you have the href
});

See it in action: JSFiddle