Re: [xmlvm-users] Default values of member variables

[Arno P. <ar...@pu...>]

OK, I just committed a fix for this problem. Static members were a 
little tricker but it should work now. The XMLVM demos work.

Arno


Markus Heberling wrote:
> Hi, 
> 
> I have tested it with a port of microemulator (http://microemu.org). 
> Worked fine for me there. Will try out the xmlvm demos tonight, too. 
> 
> Markus
> 
> Von meinem iPhone gesendet
> 
> Am 03.11.2009 um 16:38 schrieb Wolfgang Korn <wol...@xm... 
> <mailto:wol...@xm...>>:
> 
>> Markus,
>>
>> sorry for the late reply. At a first glance I don't see problems with 
>> the patch you sent. Did you try running the demo applications shipped 
>> with XMLVM to make sure that the patch did not break something or did 
>> you only try running your small sample program?
>>
>> -- Wolfgang
>>
>>
>> Markus Heberling wrote:
>>> Hi,
>>>
>>> what about this patch:
>>>
>>> @@ -183,11 +183,35 @@ int main(int argc, char* argv[])
>>>      <xsl:text>
>>>  @implementation </xsl:text>
>>>      <xsl:value-of select="vm:fixname(@package)"/>
>>>      <xsl:text>_</xsl:text>
>>>      <xsl:value-of select="vm:fixname(@name)"/>
>>> -
>>> +
>>> +
>>> +    <!-- Emit constructor -->
>>> +    <xsl:text>
>>> +-(id)init
>>> +{
>>> +    if (self = [super init])
>>> +    {
>>> +</xsl:text>
>>> +      <!-- Emit declarations for all non-static object fields -->
>>> +      <xsl:for-each select="vm:field[not(@isStatic = 'true') and 
>>> vm:isObjectRef(@type)]">
>>> +          <xsl:text>        </xsl:text>
>>> +        <xsl:value-of select="vm:fixname(../@package)"/>
>>> +        <xsl:text>_</xsl:text>
>>> +        <xsl:value-of select="vm:fixname(../@name)"/>
>>> +        <xsl:text>_</xsl:text>
>>> +        <xsl:value-of select="vm:fixname(@name)"/>
>>> +        <xsl:text>=[NSNull null];
>>> +</xsl:text>
>>> +      </xsl:for-each>
>>> +<xsl:text>    }
>>> +    return self;
>>> +}
>>> +</xsl:text>
>>> +
>>>      <!-- Emit destructor -->
>>>      <xsl:text>;
>>>
>>>  - (void) dealloc;
>>>  {
>>>
>>>
>>> This creates a constructor in the ObjC-class and fills all instance 
>>> variables of any Object-type with [NSNull null].
>>>
>>> This seems to work in my tests, but I don't know if it might break 
>>> anything.
>>>
>>> Markus
>>>
>>> Am 30.10.2009 um 20:18 schrieb Arno Puder:
>>>
>>>>
>>>> this is a tricky issue. Objective-C initializes member variables to
>>>> 'nil' by default (which, I believe, is represented by 0x0). However, in
>>>> XMLVM we cannot map Java's null to Objective-C's nil, because nil is 
>>>> not
>>>> accepted as an argument to some data structures (e.g., NSArray,
>>>> NSDictionary, etc). That is why we map null to [NSNull null].
>>>>
>>>> Now, very unfortunate, you cannot do something like this in 
>>>> Objective-C:
>>>>
>>>> @interface Foo {
>>>> id ref = [NSNull null];
>>>> }
>>>> @end
>>>>
>>>> This means, you have do some fancy code generation. This is a known
>>>> issue in XMLVM. In the meantime, you can explicitly initialize Java
>>>> members such as:
>>>>
>>>> public class Test {
>>>>   Object ref = null;
>>>> ...
>>>>
>>>> Arno
>>>>
>>>>
>>>> Panayotis Katsaloulis wrote:
>>>>> On 30 Οκτ 2009, at 8:35 μ.μ., Markus Heberling wrote:
>>>>>
>>>>>> Hi,
>>>>>>
>>>>>> take this code convert it to objc and run it:
>>>>>>
>>>>>> public class Test{
>>>>>>  Object thisIsNotInitialized;
>>>>>>
>>>>>>  void test(){
>>>>>>       if(thisIsNotInitialized==null)
>>>>>>           System.out.println("null");
>>>>>>  }
>>>>>>
>>>>>>  public static void main(String[] args){
>>>>>>      new Test().test();
>>>>>>  }
>>>>>> }
>>>>>>
>>>>>> I would expect to get "null" printed to the console. But that
>>>>>> doesn't happen. The generated if is something like thos:
>>>>>>
>>>>>> if (_op1.o != [NSNull null]) goto label0;
>>>>>>
>>>>>> So it checks for [NSNull null]. But _op1.o contains 0x0 and the
>>>>>> check is false. So I would guess that the initialization code of the
>>>>>> ObjC variables has to be changed so that they contain [NSNull null]
>>>>>> and not 0x0 by default.
>>>>>>
>>>>>> Hope you get what I mean.
>>>>>
>>>>>
>>>>>
>>>>> If a selector returns nil, what is seen in Java?
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