CODEWITHSUNDEEP
javascriptdojoscope
Ayyoudy
Ayyoudy

Reputation: 3721

Dojo.hitch() scope question

Why is it that when I use the dojo.hitch function and try to reference the "this" operator inside it, that it gives me reference to the wrong object?

console.debug(dijit.byId("widgetName"));  //works as expected and prints out the window object

dojo.hitch(dijit.byId("widgetName"), tester())();   //this should be executing the tester function in the scope of the widget object

function tester() {
    console.debug(this);    //prints out the Javascript Window object instead of the widget object!!!!
}

Thanks

Upvotes: 2

Views: 6120

Answers (1)

Layke
Layke

Reputation: 53206

Based on what you have just shown, I can now safely provide an answer explaining what is wrong.

When you do a dojo.hitch() you should not call the function inside of it, but instead call the result of the function. That is, you need to provide dojo.hitch with a reference to the function to hitch, not the result of invoking that function.

In your example, you are calling tester() (which invokes the function tester) inside of the dojo.hitch(), which calls the tester once. Even though you have dojo.hitch()(); because tester() does not return a function handler (but the result of tester, in this case undefined), the hitch()(); does nothing. That might have been confusing so I will show you with an example.

Don't do this:

dojo.hitch( context, handler() )();

Instead do this:

dojo.hitch( context, handler )();

So to make what you have very readable you would do this:

widget = dijit.byId("widgetName"); 
tester = function() {
    console.log(this);
}

handle = dojo.hitch(widget, tester);
handle();

Your mistake was trying to call the function from within the dojo.hitch(). This mistake also was not present in your original question.

Upvotes: 6

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