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Michael G..

Namespace Problem (I think)

in Using jQuery • 8 years ago

Hi,

I've got a problem wich is based on namespaces conventions, I think.

Here is a function from inside the $(document).ready():

var onGetGroups = function( response ) {
userGroups = response;
console.log( userGroups.data.length );
for( var i = 0; i < userGroups.data.length; i++ ) {
console.log( userGroups.data[i].name );
$( '#allGroups' ).append( '<li class="ui-selectable" id="' + userGroups.data[i].id + '">' + userGroups.data[i].name + '</li>' );
$( '#allGroups' ).selectable( { filter: "li", selected: function( event, ui ) {
$( ".ui-selected", this ).each( function() {
var index = $( '#allGroups li' ).attr( 'id' );
var name = $( '#allGroups li' ).textContent;
sg.push({id: index, name:name}); // PROBLEM!!
} );
} } );
}
console.log( sg );
};

You can see my problem on line 12. This sg object is defined directly after the ready state but I can't change it from this position in code. I always get an error: "Uncaught TypeError: Cannot read property 'push' of undefined", wich is, as I think, a problem of namespaces.

$( document ).ready( function() {
var accessToken, uid, userGroups, sg = {};

I think the sg var is global and can get accessed from everywhere in the code. But it isn't. Where is my fault?

- Thx, Michael

Replies(12)

jay.blanc..

Re: Namespace Problem (I think)

8 years ago

It isn't about namespaces (that is more typically heard in OOP) it is about variable scope. One of the most well written outlines on variable scope is here - http://stackoverflow.com/questions/500431/what-is-the-scope-of-variables-in-javascript

Michael G..

Re: Re: Namespace Problem (I think)

8 years ago

Thanks for replying! But it doesn't help me a lot. I said namespaces but meant scope ;-)

I understand the principles of the given link, but that doesn't solve my problem.

My question is: how can I reach the variable from inside these functions, especially in this jQuery case? Is there some kind of parent.sg or something like that?

Thank you very much!

coldfusio..

Re: Namespace Problem (I think)

8 years ago

What does sg equal?

Try this code:

<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="utf-8">
<title>Title</title>
<style></style>
</head>
<body>
<script>
var sg;
sg.push("5");
console.log(sg);
</script>
</body>
</html>

The error is:
Uncaught TypeError: Cannot read property 'push' of undefined <----- Your error

Now try this code:

<script>
var sg=["3"];
sg.push("5");
console.log(sg);
</script>

Works!

Michael G..

Re: Re: Namespace Problem (I think)

8 years ago

Nope! It doesn't, because you forgot to call the variable from within a (or two) function. Look at my code. sg = {} should also work properly in you shown case, but doesn't in mine. The scope ist the problem and I didn't know hoe to reach these var outside the functions scope. In your case the errors means, that the variable you want to push to isn't an object or array. that has nothing to do with my problem, sorry!

but thanks for your replay and solution!

coldfusio..

Re: Namespace Problem (I think)

8 years ago

Michael,

Show me how to construct an example such that this code works:

<script>
var sg; // The way you declare sg
sg.push({index:5});
console.log(sg);
</script>

I intentionally left out the scope issue, because I felt the problem is more fundamental.

Michael G..

Re: Re: Namespace Problem (I think)

8 years ago

Yea, you have to, sorry! Because I haven't said, that I have tried such things like sg = {} or sg = []

watusiware

Re: Namespace Problem (I think)

8 years ago

I am skeptical about what you have stated:

Here is a function from inside the $(document).ready()

Is it? Can't prove it to me, because you haven't posted the complete code. Is the other piece of code that you posted inside the *same* $(document).ready() callback?

I am always skeptical when somebody posts little bits and pieces of code. The problem is almost *always* in the parts that the poster thought we didn't need to see.

Can you post a link to your page, or else set up a jsFiddle? That way we can see the page in it's entirety, and try it out.

This is not true:

I think the sg var is global and can get accessed from everywhere in the code.

Declared variables are scoped to the function in which they are declared. You can access your variable from anywhere within the *same* function in which you declared it. (Including nested functions.)

Michael G..

Re: Re: Namespace Problem (I think)

8 years ago

http://jsfiddle.net/ovwg8msr/2/ hope it helps. Note: I was a little playing, so the code looks different ;-)

watusiware

Re: Namespace Problem (I think)

8 years ago

As I suspected, things are not as described.

First off, you haven't defined any variables at all. Since you haven't used var to declare them, your variables are, in fact, global.

I can't do anything with your fiddle, though. Can you create an example that doesn't have to access Facebook? I suspect you have a cross-domain Ajax issue to deal with (I get a "frame was blocked" error). Can we take that out of the equation and solve your scoping problem?

Edit: I suppose not, since the purpose of the code is to do a POST to Facebook. Are you sure you are using their API correctly? Did you seek advice from Facebook developer documentation and forums?

I notice that you try to interate through sg. But you never set a value in sg. Of course, if you iterate through nothing, the code will do nothing.

I'd start with a known working example of the Facebook POST you are trying to do. We can't help much with that here.

Michael G..

Re: Re: Namespace Problem (I think)

8 years ago

ok, tried my best ;-)

http://jsfiddle.net/94n18799/

watusiware

Re: Namespace Problem (I think)

8 years ago

It appears your new Fiddle is empty.

Edit: sorry, strange. Nothing (not even the source) shows until you hit "run". I've never seen that happen before.

Hmmmm... the Fiddle doesn't appear to be usable. I don't know why. The button never appears.

Your variables are global variables. There is no issue with scope. Your problem seem related to using the Facebook API. We aren't experts on that here. It looks to me, though, that you are trying to use the API before it has loaded.

Most APIs of this nature have some sort of "ready" callback of their own, which is called once the API Javascript code has been loaded and is ready to accept requests. You need to research and use this.

Michael G..

Re: Re: Namespace Problem (I think)

8 years ago

that's of course is a possibility. Thx!

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