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

[Markus H. <ma...@ti...>]

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...>:

> 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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