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|
return_reference_to
-------------------
Motivation
~~~~~~~~~~
It is very common to return references to arguments or the this-pointer to
allow for chaining in C++.
::
struct A
{
float val;
A& set(float v)
{
val = v;
return *this;
}
};
When luabind generates code for this, it will create a new object for the
return-value, pointing to the self-object. This isn't a problem, but could be a
bit inefficient. When using the return_reference_to-policy we have the ability
to tell luabind that the return-value is already on the lua stack.
Defined in
~~~~~~~~~~
.. parsed-literal::
#include <luabind/return_reference_to_policy.hpp>
Synopsis
~~~~~~~~
.. parsed-literal::
return_reference_to(index)
Parameters
~~~~~~~~~~
========= =============================================================
Parameter Purpose
========= =============================================================
``index`` The argument index to return a reference to, any argument but
not ``result``.
========= =============================================================
Example
~~~~~~~
.. parsed-literal::
struct A
{
float val;
A& set(float v)
{
val = v;
return \*this;
}
};
module(L)
[
class_<A>("A")
.def(constructor<>())
.def("set", &A::set, **return_reference_to(_1)**)
];
.. warning::
This policy ignores all type information and should be used only it
situations where the parameter type is a perfect match to the
return-type (such as in the example).
|
