[Laszlo-user] Laszlo function as Array.sort argument

[Pablo Kang]

Makes sense. Thanks Tucker!


On Wed, 9 Jan 2008, P T Withington wrote:

> It _is_ getting called.  For some reason, your Debug.write is failing to send 
> any output:
>
> lzx> Debug.trace(canvas, 'laszloMethod')
> lzx> [1,2,3].sort(canvas.laszloMethod)
> TRACE: [394491.00] laszloMethod.apply(«undefined», [1, 2])
> laszloMethod( 1 , 2 )
> TRACE: [394501.00] laszloMethod -> 0
> TRACE: [394505.00] laszloMethod.apply(«undefined», [1, 3])
> laszloMethod( 1 , 3 )
> TRACE: [394512.00] laszloMethod -> 0
> TRACE: [394516.00] laszloMethod.apply(«undefined», [1, 2])
> laszloMethod( 1 , 2 )
> TRACE: [394523.00] laszloMethod -> 0
> TRACE: [394527.00] laszloMethod.apply(«undefined», [2, 3])
> laszloMethod( 2 , 3 )
> TRACE: [394536.00] laszloMethod -> 0
> «Array(3)#15| [1, 2, 3]»
> lzx>
>
> Oh, hah-hah.  I see why.  Because laslzoMethod is a method, it expects a 
> 'this' argument, and our compiler inserts an implicit `with (this)` around 
> your method body, but you are calling it as a function, and `this` is 
> undefined in that case (see the trace output above).  So your code is turning 
> into `with (undefined)` and I bet that causes the global reference to Debug 
> to fail.  Amusingly, tracing the method makes the debug output work.  I can't 
> really explain that.
>
> If you were to make a closure to call your method, it should work:
>
> lzx> Debug.untrace(canvas, 'laszloMethod')
> lzx> [1,2,3].sort(function (a, b) { return canvas.laszloMethod(a, b) })
> laszloMethod( 1 , 2 )
> laszloMethod( 1 , 3 )
> laszloMethod( 1 , 2 )
> laszloMethod( 2 , 3 )
> «Array(3)#57| [1, 2, 3]»
> lzx>
>
> On 2008-01-09, at 14:28 EST, Pablo Kang wrote:
>
>> Btw, I know that I can call a laszloMethod from a Javascript function like:
>> 
>> <method name="javascriptFunction" args="n1,n2">
>>     return canvas.laszloMethod(n1,n2);
>> </method>
>> 
>> What I want to know is why it is I can't pass in the the laszloMethod 
>> directly.
>> 
>> Thanks,
>> pablo
>> 
>> On Wed, 9 Jan 2008, Pablo Kang wrote:
>> 
>>> Anyone know why passing in a function defined with an LZX method tag into 
>>> Array.sort doesn't work? Here's a test case:
>>> 
>>> <canvas debug="true">
>>>
>>>  <method name="laszloMethod" args="n1,n2">
>>>      Debug.write('laszloMethod(', n1, ',', n2, ')');
>>>      return 0;
>>>  </method>
>>>
>>>  <script>
>>>      function javascriptFunction(n1,n2) {
>>>          Debug.write('javascriptFunction(', n1, ',', n2 ,')');
>>>          return 0;
>>>      }
>>>  </script>
>>>
>>>  <handler name="oninit">
>>>      var arr = [ 1,2,3 ];
>>>
>>>      Debug.write('-- Javascript Function --');
>>>      arr.sort( javascriptFunction );
>>>
>>>      Debug.write('-- Laszlo Method --------');
>>>      arr.sort( canvas.laszloMethod );
>>>  </handler>
>>> 
>>> </canvas>
>>> 
>>> pablo
>>> 
>>> 
>>> 
>