Re: [Swig-user] Wrapping abstract class

[Rubyo <ste...@gm...>]

William S Fulton ha scritto:
> Rubyo wrote:
>> Juan Manuel Alvarez wrote:
>>>> Hi everyone!
>>>>
>>>> I am trying to wrap an abstract class to C#, but I always get the
>>>> "cannot instantiate abstract class" error, since SWIG generates a
>>>> construction function.     
> This shouldn't happen by default. Please show a minimal example 
> demonstrating the problem if you want any more advice.
>
>>> You should be able to turn off automatic constructor generation with 
>>> the
>>> %nodefaultctor feature flag directive. See the manual: 
>>> http://www.swig.org/Doc1.3/SWIGDocumentation.html#SWIGPlus_nn8
>>>
>> I'm trying to solve the same situation..
>> ..the problem is tha you don't have the body of the pure virtual 
>> function .. so eliminating the constructor is not a solution ... I 
>> think ...( or I'm wrong ? )...swig  translate the abstract class as a 
>> usual class  ( not interface! ) and try to instantiate it anyway... 
>> so you get that error ... or is there  some news on that?
>>
>> anyway in the manul page you read .. "Default constructors are not 
>> generated for classes with pure virtual methods or for classes that 
>> inherit from an abstract class, but don't provide definitions for all 
>> of the pure methods."...
>>
>
> Stefano, I have an example of how to wrap abstract base classes which 
> I've pasted below. It is for Java, but with a bit of modification can 
> be made to work for C#. Just modify the typemap names as described in 
> the CSharp.html documentation, eg javabody->csbody. The example shows 
> how multiple inheritance can be made to work, even though there is a 
> lot of swig machinery to write. As Zhiyang Jiang mentioned in another 
> thread, he might be able to modify swig so that just one line of code 
> can replace all of the typemaps and features below.
>
> William
>
> /* File : example.i */
> %module example
>
> // Turn the proxy class into an interface
> %typemap(javaclassmodifiers) IRemoteSyncIO "interface";
> %typemap(javaclassmodifiers) IRemoteAsyncIO "interface";
> %typemap(javabody) IRemoteSyncIO "";
> %typemap(javabody) IRemoteAsyncIO "";
> %typemap(javafinalize) IRemoteSyncIO "";
> %typemap(javafinalize) IRemoteAsyncIO "";
> %typemap(javadestruct) IRemoteSyncIO "";
> %typemap(javadestruct) IRemoteAsyncIO "";
>
> // Turn the methods into abstract methods
> %javamethodmodifiers IRemoteSyncIO::syncmethod "abstract public";
> %javamethodmodifiers IRemoteAsyncIO::asyncmethod "abstract public";
> %typemap(javaout) void IRemoteSyncIO::syncmethod ";"
> %typemap(javaout) void IRemoteAsyncIO::asyncmethod ";"
>
> // Features are inherited by derived classes, so override this
> %javamethodmodifiers RemoteMpe::syncmethod "public"
> %javamethodmodifiers RemoteMpe::asyncmethod "public"
>
> // Modify multiple inherited base classes into inheriting interfaces
> %typemap(javainterfaces) RemoteMpe "IRemoteSyncIO, IRemoteAsyncIO";
> %typemap(javabase, replace="1") RemoteMpe "";
>
>
> %inline %{
> class IRemoteSyncIO
> {
> public:
>   virtual ~IRemoteSyncIO () {}
>   virtual void syncmethod() = 0;
> protected:
>   IRemoteSyncIO () {}
>
> private:
>   IRemoteSyncIO (const IRemoteSyncIO&);
>   IRemoteSyncIO& operator= (const IRemoteSyncIO&);
> };
>
> class IRemoteAsyncIO
> {
> public:
>   virtual ~IRemoteAsyncIO () {}
>   virtual void asyncmethod() = 0;
> protected:
>   IRemoteAsyncIO () {}
>
> private:
>   IRemoteAsyncIO (const IRemoteAsyncIO&);
>   IRemoteAsyncIO& operator= (const IRemoteAsyncIO&);
> };
>
> class RemoteMpe : public IRemoteSyncIO, public IRemoteAsyncIO
> {
> public:
>   virtual void syncmethod() {}
>   virtual void asyncmethod() {}
> };
>
> %}
>
Thank you William,
                                I'm studing this code in my use 
case...(soon some try)
Obviously Zhiyang Jiang's work will be greatly appreciated...

Stefano