Functions: call / apply / f()

[Philippe Poulard]

Hi folks !

I have some code like this that passes an anonymous function:
foo.bar(p1, function(p2) {
alert(p2);
});

in foo.bar, i create a button with a listener; when it is executed, the
following code fails to run:

bar : function(somePara, someFunction) {
...
someButton.addListener("execute", function(e) {
someFunction(someData);
});
...
}

I google for some documentation and this version works well:

bar : function(somePara, someFunction) {
...
someButton.addListener("execute", function(e) {
someFunction.call(null, someData);
});
...
}

I don't understand the difference between f.apply(), f.call() and f()
and why the latter doesn't work

In fact, when using f("foo") the function is executed (I'm sure of that
when I insert alert("Hello")), but without its argument if in the body
of the anonymous function i use alert(p2) it fails

Please can you explain this behaviour ?

--
Cordialement,

///
(. .)
--------ooO--(_)--Ooo--------
| Philippe Poulard |
-----------------------------
http://reflex.gforge.inria.fr/
Have the RefleX !

[Martin Honnen]

Philippe Poulard wrote:

I have some code like this that passes an anonymous function:
foo.bar(p1, function(p2) {
alert(p2);
});

in foo.bar, i create a button with a listener; when it is executed, the
following code fails to run:

bar : function(somePara, someFunction) {
...
someButton.addListener("execute", function(e) {
someFunction(someData);
});
...
}

Do you get an error? Which one exactly?

I google for some documentation and this version works well:

bar : function(somePara, someFunction) {
...
someButton.addListener("execute", function(e) {
someFunction.call(null, someData);
});
...
}

I don't understand the difference between f.apply(), f.call() and f()
and why the latter doesn't work

In fact, when using f("foo") the function is executed (I'm sure of that
when I insert alert("Hello")), but without its argument if in the body
of the anonymous function i use alert(p2) it fails

Please can you explain this behaviour ?

So the alert dialog does not appear? Have you checked the error console
of the browser?
I don't see a reason why f() should fail but f.call() should execute.

--

Martin Honnen
http://JavaScript.FAQTs.com/

[Philippe Poulard]

Martin Honnen a écrit :

Philippe Poulard wrote:

>I have some code like this that passes an anonymous function:
foo.bar(p1, function(p2) {
alert(p2);
});

in foo.bar, i create a button with a listener; when it is executed, the
following code fails to run:

bar : function(somePara, someFunction) {
...
someButton.addListener("execute", function(e) {
someFunction(someData);
});
...
}

Do you get an error? Which one exactly?

No because it is trapped by the framework within which it is executed
(that doesn't log it correctly); but it fails because i don't get the
alert box (I'm sure the block is executed because if I insert
alert("Hello"); before alert(p2); I see the former but not the latter)

Therefore, it seems that a reference to p2 make all the stuff crashing

>

>I google for some documentation and this version works well:

bar : function(somePara, someFunction) {
...
someButton.addListener("execute", function(e) {
someFunction.call(null, someData);
});
...
}

I don't understand the difference between f.apply(), f.call() and f()
and why the latter doesn't work

In fact, when using f("foo") the function is executed (I'm sure of
that when I insert alert("Hello")), but without its argument if in the
body of the anonymous function i use alert(p2) it fails

Please can you explain this behaviour ?

So the alert dialog does not appear? Have you checked the error console
of the browser?
I don't see a reason why f() should fail but f.call() should execute.

ok, so it's not my fault :)
since f.call() works, I have changed to it in my code

--
Cordialement,

///
(. .)
--------ooO--(_)--Ooo--------
| Philippe Poulard |
-----------------------------
http://reflex.gforge.inria.fr/
Have the RefleX !