How to set angular controller object property value from directive in child scope

Solution 1:

$parse will solve your problem.

<button ng-update1="inputdata.title">

app.directive('ngUpdate1', function($parse) {
    return function(scope, element, attrs) {
        var model = $parse(attrs.ngUpdate1);
        console.log(model(scope));  // logs "test"
        element.bind('click', function() {
           model.assign(scope, "Button 1");
           scope.$apply();
        });
    };
});

Fiddle

Whenever a directive does not use an isolate scope and you specify a scope property using an attribute, and you want to modify the value, use $parse.

If you don't need to modify the value, you can use $eval instead:

console.log(scope.$eval(attrs.ngUpdate1));

Solution 2:

Not sure what overall objective is but one way is to create 2 attributes, one for the target object and the other for the property of that object:

<button ng-update1  obj="inputdata" prop="title">

app.directive('ngUpdate1', function() {
    return function(scope, element, attrs) {
        element.bind('click', function() {
            scope.$apply(function() {                
                scope[ attrs.obj ][attrs.prop] = "Button 1";               

            });
        });
    };
});

DEMO:http://jsfiddle.net/CSbRB/9/

Alternatively using existing format you could split() value of your current ng-update1 attribute and use result array for object and property in notation

 element.bind('click', function() {
           var target=attrs.ngUpdate1.split('.');
            scope.$apply(function() {                
                scope[ target[0] ][target[1]] = "Button 1";               

            });
        });

DEMO with both approaches: http://jsfiddle.net/CSbRB/10/

One more approach where you create an isolated scope in directive and can pass in the reference to inputdata object and pull property name from attribute(same markup as second version):

app.directive('ngUpdate3', function () {
    return {
        scope: {
           targetObject: '=obj'
        },
        link: function (scope, element, attrs) {
            element.bind('click', function () {  
               scope.$apply(function () {
                    scope.targetObject[attrs.prop]='Button 3';

                });
            });
        }
    }
});

http://jsfiddle.net/CSbRB/11/