Adapter pattern

一応自分の言葉で説明できるように、自分なりの解釈を書くようにしてるので、間違いがたぶんにあると思う。

[category]
Structural pattern.

[brief description]
This pattern translates one interface for a class into compatible interface.
=> Wrapper

[detail description]
Adapter class provides interfaces to client from incompatible classes or, this is my opinion, a new interface wrapped around a simple interface such as MFC. cf) MFC wraps Windows API about C++ interface, I think, I've never used MFC... --;

[expression in UML]
                               ┌───────┐
                               │   Adaptee    │
                               ├───────┤
                               ├───────┤
                               │+ methodB()   │
                               └───────┘
                                       ↑
                                       │
                                       │
┌───────┐             ┌───────┐
│    Client    │──────>│   Adapter    │
├───────┤             ├───────┤
│- adapter     │             │- adaptee     │
│   : Adapter  │             │   : Adaptee  │
├───────┤             ├───────┤
│+ doWork()    │             │+ methodA()   │
└───────┘             └───────┘
       │                              │
       │                              │
       ↓                              ↓
┌─ doWork()   ───┐       ┌─ methodA()  ───┐
│                    │       │                    │
│ adapter.methodA()  │       │ adaptee.methodB()  │
│                    │       │                    │
└──────────┘       └──────────┘

[sample code]

(C++)

#include <iostream>
//---- this is adaptee classes for other file
struct Point
{
    Point(int x_, int y_) : x(x_), y(y_) {}
    int x;
    int y;
};

std::ostream& operator<<(std::ostream& ost, Point p)
{
    ost << "(" << p.x << "," << p.y << ")";
    return ost;
}

class LinePrinter
{
  public:
    void printLine(Point* a, Point* b)
    {
        std::cout << "draw line from " << *a << " to " << *b << std::endl;
    }

    void printRectangle(Point* a, Point* b)
    {
        std::cout << "draw rectangle from " << *a << " to " << *b << std::endl;
    }
};
//---- end adaptee classed

//---- these are adapter
class Shape
{
  public:
    Shape(int x1, int x2, int y1, int y2)
         : p1(x1, y1), p2(x2, y2)
    {}
    virtual ~Shape() {}

    virtual void draw() = 0;
  protected:
    void setPrinter(LinePrinter* printer_)
    {
        printer = printer_;
    }
    LinePrinter* printer;

    Point p1;
    Point p2;
};

class Line
     : public Shape
{
  public:
    Line(int x1, int x2, int y1, int y2)
         : Shape(x1, x2, y1, y2)
    {
        setPrinter(new LinePrinter());
    }
    virtual ~Line() {}

    virtual void draw()
    {
        printer->printLine(&p1, &p2);
    }
};

class Rectangle
     : public Shape
{
  public:
    Rectangle(int x1, int x2, int y1, int y2)
         : Shape(x1, x2, y1, y2)
    {
        setPrinter(new LinePrinter());
    }
    virtual ~Rectangle() {}

    virtual void draw()
    {
        printer->printRectangle(&p1, &p2);
    }
};
//---- end adapter

int main(int, char**)
{
    Shape *line = new Line(0, 0, 10, 5);
    Shape *rect = new Rectangle(0, 0, 10, 10); // must be square

    line->draw();
    rect->draw();

    delete line;
    delete rect;

    return 0;
}