[C++-sig] Boost.Python : Return std::string by ref?

[Brian O'Kennedy]

Hi All, 

 

I'm new to using Boost.Python so this might be a silly question, but
bear with me.  I've got a very simple c++ class as such:

 

class MyClass

{  

 public: 

   const std::string GetName() { return m_Name; };

   void SetName( const std::string & Name ) { m_Name = Name; };

 private:

   std::string m_Name;

};

 

Which I wrap using Boost.Python:

  class_ < MyClass >("MyClass", "Testing String returned by value")

     .def( "GetName", &MyClass::GetName )

     .def( "SetName", &MyClass::SetName);

 

And I get to use it in Python as expected:

>>> import BoostPythonTest

>>> a = BoostPythonTest.MyClass()

>>> a.SetName("foo")

>>> a.GetName()

'foo'

>>> type(a.GetName())

<type 'str'>

>>> ^Z

 

The problem comes when I try to wrap this:

class MyOtherClass

{  

public: 

  const std::string & GetName() { return m_Name; };

  void SetName( const std::string & Name ) { m_Name = Name; };

private:

  std::string m_Name;

};

 

Notice that GetName() now returns the string by const reference; this is
done in a lot of our c++ code for efficiency sake. To wrap this using
Boost.Python I do:

  class_ < MyOtherClass >("MyOtherClass", "Testing String returned by
const ref")

      .def( "GetName", &MyOtherClass::GetName,
return_internal_reference<>() )

      .def( "SetName", &MyOtherClass::SetName);

 

Which when used in Python does:

>>> import BoostPythonTest

>>> a = BoostPythonTest.MyOtherClass()

>>> a.SetName('bar')

>>> a.GetName()

Traceback (most recent call last):

  File "<stdin>", line 1, in <module>

TypeError: No Python class registered for C++ class class
std::basic_string<char,struct std::char_traits<char>,class
std::allocator<char> >

 

Is it possible to make Boost.Python automatically convert that const
std::string & into a python string?  Assume that I cannot go changing
the c++ code of the classes that I want to wrap.  

 

Thanks, 

 Brian

 

 


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