ObjectiveC中的继承

#import <Foundation/Foundation.h>

// --------------------------------------------------
// constants for the different kinds of shapes and their colors

typedef enum {
    kRedColor,
    kGreenColor,
    kBlueColor
} ShapeColor;


// --------------------------------------------------
// Shape bounding rectangle


typedef struct {
    int x, y, width, height;
} ShapeRect;


// --------------------------------------------------
// convert from the ShapeColor enum value to a human-readable name

NSString *colorName (ShapeColor color)
{
    NSString *colorName;
    
    switch (color) {
        case kRedColor:
            colorName = @"red";
            break;
        case kGreenColor:
            colorName = @"green";
            break;
        case kBlueColor:
            colorName = @"blue";
            break;
        default:
            colorName = @"oops! Unexpected color";
            break;
    }
    
    return (colorName);
    
} // colorName


// --------------------------------------------------
// Shapes base class

@interface Shape : NSObject
{
    ShapeColor  fillColor;
    ShapeRect   bounds;
}

- (void) setFillColor: (ShapeColor) fillColor;
- (void) setBounds: (ShapeRect) bounds;
- (void) draw;

@end // Shape


@implementation Shape

- (void) setFillColor: (ShapeColor) c
{
    fillColor = c;
} // setFillColor

- (void) setBounds: (ShapeRect) b
{
    bounds = b;
} // setBounds

- (void) draw
{
} // draw

@end // Shape




// --------------------------------------------------
// All about Triangles

@interface Triangle : Shape
@end // Triangle


@implementation Triangle

- (void) draw
{
    NSLog (@"drawing a triangle at (%d %d %d %d) in %@",
           bounds.x, bounds.y, 
           bounds.width, bounds.height,
           colorName(fillColor));
} // draw

@end // Triangle




// --------------------------------------------------
// All about Circles

@interface Circle : Shape
@end // Circle


@implementation Circle

- (void) draw
{
    NSLog (@"drawing a circle at (%d %d %d %d) in %@",
           bounds.x, bounds.y, 
           bounds.width, bounds.height,
           colorName(fillColor));
} // draw

@end // Circle




// --------------------------------------------------
// All about Rectangles

@interface Rectangle : Shape
@end // Rectangle


@implementation Rectangle

- (void) draw
{
    NSLog (@"drawing a rectangle at (%d %d %d %d) in %@",
           bounds.x, bounds.y, 
           bounds.width, bounds.height,
           colorName(fillColor));
} // draw

@end // Rectangle


// --------------------------------------------------
// All about OblateSphereoids

@interface OblateSphereoid : Shape
@end // OblateSphereoid


@implementation OblateSphereoid

- (void) draw
{
    NSLog (@"drawing an egg at (%d %d %d %d) in %@",
           bounds.x, bounds.y, 
           bounds.width, bounds.height,
           colorName(fillColor));
} // draw

@end // OblateSphereoid



// --------------------------------------------------
// Draw the shapes

void drawShapes (id shapes[], int count)
{
    for (int i = 0; i < count; i++)
    {
        id shape = shapes[i];
        [shape draw];
    }
    
} // drawShapes



// --------------------------------------------------
// The main function.  Make the shapes and draw them

int main (int argc, const char * argv[]) 
{
    id shapes[4]; // I'm different!
    
    ShapeRect rect0 = { 0, 0, 10, 30 };
    shapes[0] = [Circle new];
    [shapes[0] setBounds: rect0];
    [shapes[0] setFillColor: kRedColor];
    
    ShapeRect rect1 = { 30, 40, 50, 60 };
    shapes[1] = [Rectangle new];
    [shapes[1] setBounds: rect1];
    [shapes[1] setFillColor: kGreenColor];
    
    ShapeRect rect2 = { 15, 19, 37, 29 };
    shapes[2] = [OblateSphereoid new];
    [shapes[2] setBounds: rect2];
    [shapes[2] setFillColor: kBlueColor];
    
    ShapeRect rect3 = { 47, 32, 80, 50 };    // I'm new!
    shapes[3] = [Triangle new];
    [shapes[3] setBounds: rect3];
    [shapes[3] setFillColor: kRedColor];
    
    drawShapes (shapes, 4); // I'm different!
    
    return (0);
    
} // main