Properties in C++

A long time ago when I was working on Borland C++ and Delphi was just a baby, we added properties as a language extension to C++. Nobody at the C++ committee liked the notion (not sure why, but Java didn't like it either), but I came up with a way of doing properties in C++ using templates. Here is the property class:

enum PropertyType {READ_ONLY, WRITE_ONLY, READ_WRITE};

template <typename Container, typename ValueType, PropertyType Type>

class Property {

private:

    Container* FObject;

    void (Container::*FSetter)(ValueType value);

    ValueType (Container::*FGetter)();

    

public:

    Property() {

        FObject = NULL;

        FSetter = NULL;

        FGetter = NULL;

    }

    

    void InitializeSetterGetter(Container* Value,

                                void (Container::*Setter)(ValueType Value),

                                ValueType (Container::*Getter)()) {

        assert(Type == READ_WRITE);

        FObject = Value;

        FSetter = Setter;

        FGetter = Getter;

    }

    void InitializeSetter(Container* Value,

                          void (Container::*Setter)(ValueType Value)) {

        assert(Type == WRITE_ONLY);

        FObject = Value;

        FSetter = Setter;

    }

    void InitializeGetter(Container* Value,

                          ValueType (Container::*Getter)()) {

        assert(Type == READ_ONLY);

        FObject = Value;

        FGetter = Getter;

    }

    

    // To set the value using the set method.

    ValueType operator =(const ValueType& Value) {

        assert(FObject != NULL);

        assert(FSetter != NULL);

        (FObject->*FSetter)(Value);

        return Value;

    }

    

    // The Property class is treated as the internal type.

    operator ValueType() {

        assert(FObject != NULL);

        assert(FGetter != NULL);

        return (FObject->*FGetter)();

    }

};

Now, to use this, call one of the Initializer* functions from within your classes constructor, provide getter and setter methods and instantiate the property as follows:

class TestProperty {

protected:

    std::string FMyProperty;

    

public:

    TestProperty() {

        MyProperty.InitializeGetter(this,

                                    &TestProperty::SetMyProperty

                                    &TestProperty::GetMyProperty);

    }

    std::string GetMyProperty() {

        return FMyProperty;

    }

    void SetMyProperty(std::string Value) {

        FMyProperty = Value

    }

    

    Property<Process, std::string, READ_WRITE> MyProperty;

};

It's a bit more work than if you were to use a language that supports properties such as Delphi or C#, but it can be a very handy syntactic sugar.