RWModel

Module:  Essential Tools Module   Group:  Miscellaneous Classes

Does not inherit

• Local Index
• Synopsis
• Description
• Persistence
• Example
• Public Constructor
• Public Member Functions

Members

addDependent()

changed()

removeDependent()

RWModel()

#include <rw/model.h>
(abstract base class)

This abstract base class has been designed to implement the "Model" leg of a Model-View-Controller architecture. A companion class, RWModelClient, supplies the "View" leg.

It maintains a list of dependent RWModelClient objects. When member function changed(void*) is called, the list of dependents will be traversed, calling updateFrom(RWModel*, void*) for each one, with itself as the first argument. Subclasses of RWModelClient should be prepared to accept such a call.

None

This is an incomplete and somewhat contrived example in that it does not completely define the classes involved. "Dial" is assumed to be a graphical representation of the internal settings of "Thermostat." The essential point is that there is a dependency relationship between the "Thermostat" and the "Dial": when the setting of the thermostat is changed, the dial must be notified so that it can update itself to reflect the new setting of the thermostat.

#include <iostream>
#include <rw/model.h>

class Dial : public RWModelClient
{
    int dialNumber;
public:
    explicit
    Dial(int /* dialNumber */);
    virtual void 
    updateFrom(RWModel* /* m */, void* /* d */);
};


class Thermostat : public RWModel
{
    double setting;
public:
    Thermostat( Dial* d ) { 
        addDependent (d); 
        setting = 0; 
    }
    double temperature() const { 
        return setting; 
    }
    void setTemperature(double t) { 
        setting = t; 
        changed (); 
    }
};


void Dial::updateFrom(RWModel* m, void*)
{
    Thermostat* t = (Thermostat*)m;
    double temp = t -> temperature ();

    // Redraw graphic.
    std::cout << "Dial #" << dialNumber << " says " << temp << std::endl;
}

Dial::Dial (int num) : dialNumber (num)
{
}

int main ()
{
    Dial one(1);
    Dial two(2);

    Thermostat therm(&one);

    therm.setTemperature(77);
    therm.setTemperature(-4);
    therm.addDependent(&two);
    therm.setTemperature(47); 
    return 0;
}

Program output:

Dial #1 says 77
Dial #1 says -4
Dial #1 says 47
Dial #2 says 47

RWModel();

When called by the specializing class, sets up the internal ordered list of dependents.

void
addDependent(RWModelClient* m);

Adds the object pointed to by m to the list of dependents of self.

virtual void
changed(void* d);

Traverse the internal list of dependents, calling member function updateFrom(RWModel*, void*) for each one, with self as the first argument and d as the second argument.

void
removeDependent(RWModelClient* m);

Removes the object pointed to by m from the list of dependents of self.

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