Re: [Swig-user] Problem with the Java callback example

[William S F. <ws...@fu...>]

Fabian Bernhard wrote:
> Dear list
> 
> I'm new to Swig and have limited knowledge of it.
> 
> I have to implement an observable pattern. The observer is a Java class 
> and the notifier is implemented in C++. I can basically break the 
> problem down to the callback example provided with the Swig source code [0].
> 
> Unfortunately even the simple example does not work for me. I can 
> generate and compile both the C++ and Java code but, when I run the Java 
> application:
> 
> (1) The C++ Callback class is always equals to 0 and thus not called by 
> the Caller class
> (2) The Java Callback class is never passed down to the C++ Caller class
> 
> As a result, the line in example.h
> 
>       if (_callback) _callback->run();
> 
> is never executed (because _callback == false).
> 
> I must assume that it has either something to do with my machine 
> (GNU/Linux system with g++ 4.3.2 compiler) or something I missed due to 
> my lack of knowledge about Swig, i.e. missing compile flags.
> 
> How can I make the example work?
> 

Not sure what you are doing wrong. Below is a compile and run session 
that works. Hope that helps.

William

william@caracal:~/swig/trunk/Examples/java/callback$ g++ --version
g++ (Ubuntu 4.3.2-1ubuntu12) 4.3.2
Copyright (C) 2008 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

william@caracal:~/swig/trunk/Examples/java/callback$ java -version
java version "1.6.0_10"
Java(TM) SE Runtime Environment (build 1.6.0_10-b33)
Java HotSpot(TM) Server VM (build 11.0-b15, mixed mode)

william@caracal:~/swig/trunk/Examples/java/callback$ make clean all && 
java runme
make -f ../../Makefile java_clean
make[1]: Entering directory 
`/home/william/swig/trunk/Examples/java/callback'
rm -f *_wrap* *~ .~* *.class `find . -name \*.java | grep -v runme.java`
rm -f core
rm -f *.o *.so
make[1]: Leaving directory `/home/william/swig/trunk/Examples/java/callback'
make -f ../../Makefile CXXSRCS='example.cxx' SWIG='../../../preinst-swig' \
	SWIGOPT='' TARGET='example' INTERFACE='example.i' java_cpp
make[1]: Entering directory 
`/home/william/swig/trunk/Examples/java/callback'
../../../preinst-swig -java -c++  example.i
g++ -c -fpic    example.cxx example_wrap.cxx 
-I"/usr/lib/jvm/java-6-sun-1.6.0.10/include" 
-I"/usr/lib/jvm/java-6-sun-1.6.0.10/include/linux"
g++ -shared    example.o example_wrap.o    -o libexample.so
make[1]: Leaving directory `/home/william/swig/trunk/Examples/java/callback'
javac *.java
Adding and calling a normal C++ callback
----------------------------------------
Callback::run()
Callback::~Callback()

Adding and calling a Java callback
------------------------------------
JavaCallback.run()
Callback::~Callback()

java exit