Re: [pygccxml-development] How to manage wrapper classes?

[Matthias B. <ba...@ir...>]

Roman Yakovenko wrote:
> First of all I think you should be able to create custom call policies.
> Take a look on this link:
> http://boost.org/libs/python/doc/v2/CallPolicies.html#CallPolicies-concept
> 
> May be, this will be enough, I am not sure.

Interesting idea. From reading the above page I couldn't say if it is 
possible or not. precall() and postcall() are supposed to manage Python 
tuples which might indicate that they cannot access the original 
arguments....? Well, anyway, I posted a message to the c++-sig list, 
let's see what the "experts" have to say about this.

>> So how should that be accomplished?
> 
> There are 2 other ways to solve this problem.
> 1. Create small wrappers in Python. I do not know exactly how it should be done.
>     But, I feel that this is the right way to go. I hope some days
> pyplusplus will have
>     3'rd tree - Python code creators ( they will generate Python code ).

I have also thought about that and I might even get away with this for 
the Maya SDK, but in general, I think the problem would be that those 
Python wrappers would only be active when the object was created on the 
Python side and not on the C++ side.

> 2. Create small wrapper in C++, in the way you did it. Just put that declaration
>     in some namespace and add it to using add_code functions. 

But as I don't want to create the wrappers manually, how could I add 
wrappers that I generate automatically to the generated source files 
(not the main file)?

> Using this
>     approach you should be carefull. There are so many cases, while exporting
>     some function to Python. By the way, do we talk about pure virtual
> functions or overloaded ones?

What do you mean? The functions are not pure virtual, they are already 
implemented in the Maya SDK and I only need to access them. They are 
neither overloaded.... maybe I didn't understand the actual question...?

>> (and how can it be guaranteed that
>> the user's wrapper code doesn't interfere with the wrapper code that
>> might already get generated by pyplusplus?)
> 
> 1. Do you still want to expose functions that returns, take by
> reference MStatus object?

Uhm, yes? (that's what my mail was about...?)

> If the answer is not then we can add replace_code function to decl_wrapper_t
> class. Then pyplusplus will generate that code.

What code would replace_code() replace?

> If the answer is yes, then you have a problem. It seems to me that pyplusplus
> contains all tools in order to solve this problem, may be it does not
> expose good interface ( we will find out, right :-) ).

I hope so. :)

Well, I hope I'll get an answer to my mail on the c++-sig list so that 
we'll see if explicit wrappers are definitely required or not.

- Matthias -