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Object properties for C++

, 19 May 2005
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A small library that gives C++ objects the ability to have properties.

Introduction

The purpose of this library is to provide object properties. Instead of coding setter and getter methods, it is better to use properties because it is a more intuitive interface. Unfortunately, C++ does not offer native properties, but they can be emulated using templates and operator overloading, with a small memory overhead.

Installation

In order to use properties, you have to do include the file "property.hpp" in your project, then use the following fragment in your code:

    #include "property.hpp"
    using namespace cpp::properties;

The library is documented using Doxygen.

Declaring properties

The main class of this library is the class 'property'. It can be used to declare a property member. For example:

    class MyClass {
    public:
        property<MyClass, int> data;

        MyClass() : data(this, &MyClass::data_changed, 5) {
        }

    protected:
        virtual void data_changed() {
        }
    };

In the above example, a property 'data' is declared. The property class has two main parameters: the type of owner class (needed in order to make a typesafe callback interface) and the type of the property value.

The property's callback (and optional initial value) must be declared at construction time. It can not be changed afterwards. Callback parameters must not be null, otherwise your application will crash.

Using properties

Usage of properties is like data members. For example:

    MyClass obj;
    obj.data = 5;
    int i = obj.data + 1;
    cout << obj.data() << endl;

Advanced options

The default property declaration declares a property that has a read-write value stored inside the property. The type of access (read-write, read-only, write-only) and the type of storage (variable or interface) can be changed by supplying different template parameters.

Interface properties are properties that don't store the value, but they call the owner object for getting and setting the value of the property.

For example, a read-write interface property must be declared like this:

    class MyClass {
    public:
        property<MyClass, int, read_write, interface> data;

        MyClass() : 
            m_data(0),
            data(this, &MyClass::data_get, &MyClass::data_set) {
        }

    private:
        int m_data;

        const int &data_get() const {
            return m_data;
        }

        void data_set(const int &value) {
            m_data = value;
        }
    };

Usage of interface properties is exactly the same as variable properties. You can do different combinations of read_write, read_only, write_only and variable, interface to provide your own taste of a property.

License

As the included readme.txt explains, it's freeware, i.e. you can do whatever you like with it, except claim it for yours (of course!).

Notes

I have modified the library so that the declaration of different flavors of properties has become simpler. It works under MS VC++ 6.0 and DevCpp 4.9.

License

This article has no explicit license attached to it but may contain usage terms in the article text or the download files themselves. If in doubt please contact the author via the discussion board below.

A list of licenses authors might use can be found here

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About the Author

Achilleas Margaritis
Software Developer (Senior)
Greece Greece
No Biography provided

Comments and Discussions

 
GeneralMy vote of 2 PinmemberColdShine24-Nov-08 10:36 
GeneralSize increase PinmemberMichel Helms22-Nov-06 0:52 
GeneralMSVC versions PinmemberErnesto Savoretti7-Jun-06 15:31 
GeneralNice, but... PinmemberYevhen Fedin26-May-05 23:11 
Generalimprovement! PinmemberAchilleas Margaritis20-May-05 2:19 
GeneralRe: improvement! PinmemberChauJohnthan20-May-05 8:05 
GeneralRe: improvement! PinmemberAchilleas Margaritis20-May-05 8:41 
GeneralMS specific solution Pinmembercmk20-May-05 0:25 
GeneralNot bad PinmemberPetar K. Shomov19-May-05 13:26 
GeneralRe: Not bad PinmemberAchilleas Margaritis19-May-05 23:00 
GeneralRe: Not bad PinmemberPetar K. Shomov20-May-05 6:29 
GeneralRe: Not bad PinmemberAchilleas Margaritis20-May-05 8:55 
GeneralRe: Not bad PinmemberPetar K. Shomov20-May-05 12:55 
GeneralRe: Not bad PinmemberAchilleas Margaritis21-May-05 3:43 
GeneralRe: Not bad PinmemberPetar K. Shomov22-May-05 8:05 
GeneralRe: Not bad PinmemberAchilleas Margaritis23-May-05 6:18 
GeneralRe: Not bad PinmemberTutu24-May-05 13:26 
GeneralRe: Not bad Pinmemberbarok25-May-05 20:52 
GeneralRe: Not bad PinmemberAchilleas Margaritis26-May-05 2:03 
GeneralRe: Not bad PinmemberAchilleas Margaritis26-May-05 1:59 
GeneralRe: Not bad PinsussAnonymous14-Jul-05 14:53 
GeneralNice PinsussAnonymous19-May-05 5:49 

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