Re: [Swig-user] Java - adding code to a constructor

[Fabien R. <fab...@cy...>]

Fabien Rohrer wrote:
> 
> 
> wsfulton wrote:
>> 
>> Fabien Rohrer wrote:
>>> Hi,
>>>
>>>
>>> I'm trying to extend a C++ third part library to Java and I can't
>>> override the code of a constructor.
>>>
>>>
>>> Let say that I have a file MyClass.hpp:
>>>
>>> class MyClass{
>>>   public:
>>>     MyClass(){
>>>       cout << "Hello" << endl;
>>>    }
>>> }
>>>
>>> Is it possible to override this constructor into the SWIG interface
>>> file?
>>>
>>> I tried something like:
>>>
>>> %ignore MyClass::MyClass();
>>> %include <MyClass.hpp>
>>> %extend MyClass {
>>>   MyClass(){
>>>     cout << "Hello World" << endl;
>>>   }
>>> };
>>>
>>> But the ignore statement is still valid when the extend statement is
>>> applied. So no constructor is generated.
>>>
>>> Can anybody help me? Any suggestion is welcome!
>>>
>> Move the %extend to above the %ignore and it will work.
>> 
>> William
>> 
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>> 
> 
> Thanks for your consideration and your quick answer. But it appears to be
> not so easy. The following code you suggest:
> 
> %extend MyClass {
>   MyClass(){
>     cout << "Hello World" << endl;
>   }
> };
> %ignore MyClass::MyClass();
> %include <MyClass.hpp>
> 
> raise the following warning:
> 
> Warning(303): %extend defined for an undeclared class MyClass.
> 
> Is there a way to declare this class before the extend statement?
> 
> Fabien Rohrer
> 

I apologize; I wrote an answer too quickly. My error was due to a missing
namespace. After a little investigation, your suggestion works but raise
another error:

module_name_wrap.cpp:1858: warning : control reaches end of non-void
function

In the module_name_wrap.cpp file, SWIG generates something like:

SWIGINTERN MyClass *new_MyClass(){
    cout << "Hello World" << endl; 
  }

This can be solved by returning an instance of the C++ object at the end of
the function: here is the final code:

%extend MyClass {
  MyClass(){
    cout << "Hello World" << endl; 
    return new MyClass();
  }
};
%ignore MyClass::MyClass();
%include <MyClass.hpp>

I hope this can help someone else.

Thanks a lot,
Fabien Rohrer
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