Properties

We are now ready to expand our point class to include access to x,y and z.

    class point : public object {
    public:
	//construction
	point(double x,double y,double z);

	//access
	double get_x() const;
	double get_y() const;
	double get_z() const;

	void set_x(double x);
	void set_y(double y);
	void set_z(double z);
    private:
	double x_,y_,z_;
    };

Above, we have implemented both read and write access to x,y and z.
We'll examine read and write access in turn:

Read access

There are three ways to expose read-access to dynamic data in a class:

• member-function
• free functions threated as member functions (first argument interpreted as this)
• member-data

in addition, there are three ways to expose read-access to global data in a class:

• free function threated as static function
• constant values
• references

Here are some examples of the different forms for access:

    //dynamic data access:
    double point::get_x();                   //member-functions
    double point::y_;                        //member-data
    double point_get_z(const point& p);      //free functions as member
    //static data access:
    double get_earth_gravity();              //free function
    3.14                                     //constant value
    static int global_var;                   //Global value

And this is how to expose the above to CliPP:

    //dynamic data access:
    cls.read("x",get_x);                     //member-functions
    cls.read("y",&y_);                       //member-data
    cls.read("z",point_get_z);               //free functions as member
    //static data access:
    cls.read("gravity",get_earth_gravity);   //free function
    cls.read("PI",3.14);                     //constant value
    cls.read("ref",boost::ref(global_var));  //reference to value

static data read access can also be made available globally:

    context* c=parser.get_context();
    //static data access:
    read(c,"gravity",get_earth_gravity);     //free function
    read(c,"PI",3.141);                      //constant value
    read(c,"ref",boost::ref(global_var));    //reference to value

Write access

There are three ways to expose write-access to dynamic data in a class:

• member-function
• free functions threated as member functions (first argument interpreted as this)
• member-data

in addition, there is two way to expose write-access to global data in a class:

• free function
• reference

    //dynamic data access:
    void point::set_x(double x);                   //member-functions
    double point::y_;                              //member-data
    void point_set_z(const point& p,double z);     //free functions as member
    //static data access:
    void set_earth_gravity(double g);              //free function
    static int global_var;                         //Global value

And this is how to expose the above to CliPP:

    //dynamic data access:
    cls.write("x",set_x);                    //member-functions
    cls.write("y",&y_);                      //member-data
    cls.write("z",point_set_z);              //free functions as member
    //static data access:
    cls.write("gravity",set_earth_gravity);  //free function
    cls.write("ref",boost::ref(global_var)); //reference to value

static data write access can also be made available globally:

    context* c=parser.get_context();
    //static data access:
    write(c,"gravity",set_earth_gravity);    //free function
    write("ref",boost::ref(global_var));     //reference to value

Read/Write access

If you want to create both read and write access, you can use the read_write function with the same restrictions as above:

    cls.read_write("x",get_x,set_x);
    cls.read_write("y",&y_,set_y);
    cls.read_write("y",&z_,&z);

Copyright © 2003-2005 Peder Holt

Permission to copy, use, modify, sell and distribute this document is granted provided this copyright notice appears in all copies. This document is provided "as is" without express or implied warranty, and with no claim as to its suitability for any purpose.