I have written another example that override the assign operator, take a look http://tiannocky.spaces.live.com/blog/cns!D80340372C1B949E!346.entry Though, the comments are in Chinese, the code is C++
Date: Mon, 19 Oct 2009 19:03:52 +0200 From: peder.holt@gmail.com To: boost@lists.boost.org Subject: [boost] [property] interest in C# like properties for C++?
I have implemented a prototype support for properties in C++. It has no space overhead as it manages to deduce the this pointer of the class owning it.
Code sample:
#include <boost/static_assert.hpp> #include <boost/property.hpp> #include <iostream>
class class_with_property { public: //Implement property template template<typename Base> class property_with_a_sensible_name : public Base { public: void set(const double& a) { //Implement setting of the variable here. m_var=a; //You can access the owner of the property's this value by calling self(), e.g. self()->refresh(); } const double& get() const { return m_var; } private: double m_var; }; void refresh() { std::cout << "Refreshed"; } //Instantiate property template. These can be reused.
BOOST_PROPERTY(class_with_property,property_with_a_sensible_name,property_name); };
//And usage: void test() { class_with_property cls; cls.property_name=54.3; BOOST_STATIC_ASSERT(sizeof(class_with_property)==sizeof(double)); }
The trick used is the following:
class my_class { public: class property_x { public: my_class* self() { //Find offset of member relative to my_class size_t offset=size_t(&((my_class*)0)->x); //Use this to deduce the address of my_class return reinterpret_cast<my_class*>(size_t(this)-offset); } }; property_x x; };
It currently support: Read/Write properties Read properties Write properties
Not supported yet: indexed properties operator overloads for properties, e.g. my_class.property*my_class.property will currently fail.
Regards Peder
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