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*********************
Type System Variables
*********************
User written code can be placed in arbitrary places using the
:doc:`inject-code <codeinjectionsemantics>` tag. To ease the binding developer
work, the injected code can make use of special variables that will be replaced
by the correct values. This also shields the developer from some |project|
implementation specifics.
Variables
=========
**%0**
Replaced by the name of the return variable of the Python method/function wrapper.
**%#**
Replaced by the name of a C++ argument in the position indicated by ``#``.
The argument counting starts with ``%1``, since ``%0`` represents the return
variable name.
**%ARGUMENT_NAMES**
Replaced by a comma separated list with the names of all arguments that were
not removed on the type system description for the method/function.
**%CONVERTTOPYTHON[CPPTYPE]**
Replaced by a |project| conversion call that converts a C++ variable of the
type indicated by ``CPPTYPE`` to the proper Python object.
**%CPPSELF**
Replaced by the wrapped C++ object instance that owns the method in which the
code with this variable was inserted.
**%FUNCTION_NAME**
Replaced by the name of a function or method.
**%PYARG_#**
Similar to ``%#``, but is replaced by the Python arguments (PyObjects)
received by the Python wrapper method.
**%PYSELF**
Replaced by the Python wrapper variable (a PyObject) representing the instance
bounded to the Python wrapper method which receives the custom code.
**%PYTHONTYPEOBJECT**
Replaced by the Python type object for the context in which it is inserted:
method or class modification.
**%RETURN_TYPE**
Replaced by the type returned by a function or method.
**%TYPE**
Replaced by the name of the class to which a function belongs. Should be used
in code injected to methods.
Example
=======
Just to illustrate the usage of the variables described in the previous
sections, below is an excerpt from the type system description of a |project|
test. It changes a method that received ``argc/argv`` arguments into something
that expects a Python sequence instead.
.. code-block:: xml
<modify-function signature="overloadedMethod(int, char**)">
<modify-argument index="1">
<replace-type modified-type="PySequence" />
</modify-argument>
<modify-argument index="2">
<remove-argument />
</modify-argument>
<inject-code class="target" position="beginning">
int argc;
char** argv;
if (!PySequence_to_argc_argv(%PYARG_1, &argc, &argv)) {
PyErr_SetString(PyExc_TypeError, "error");
return 0;
}
%RETURN_TYPE foo = %CPPSELF.%FUNCTION_NAME(argc, argv);
%0 = %CONVERTTOPYTHON[%RETURN_TYPE](foo);
for (int i = 0; i < argc; ++i)
delete[] argv[i];
delete[] argv;
</inject-code>
</modify-function>
|
