上一篇展示了如何用传统的“面向过程编程方法”，实现画“矩形”、“圆”、“椭圆”，这一篇看下如何改用OOP的方法来实现：
因为要用到“颜色”以及“矩形区域”二个枚举，先把他们抽出来单独放在CommDef.h文件中
//定义“几何形状颜色”枚举
typedef enum
{
kRedColor,
kGreenColor,
kBlueColor
} ShapeColor;
//定义“几何形状矩形区域”结构
typedef struct
{
int x,y,width,height;
} ShapeRect;
然后再定义基类Shape，注意：在obj-C中，定义一个类通常分成二部分，一部分是".h"的文件，用来申明类有哪些成员（也称为类的定义文件，类似于接口），另一部分是".m"的文件，用来提供具体实现
Shape类的申明部分如下:(Shape.h)
//
// Shape.h
// HelloWorld
//
// Created by jimmy.yang on 11-1-26.
// Copyright 2011 __MyCompanyName__. All rights reserved.
//
#import "CommDef.h"
@interface Shape : NSObject {
ShapeColor fillColor;
ShapeRect bounds;
}
- (void) setFillColor:(ShapeColor) fillColor;
- (void) setBounds:(ShapeRect) bounds;
- (void) draw;
- (NSString*) getColorName:(ShapeColor) fillColor;
@end //Shape
Shape类的实现部分如下:(Shape.m)
//
// Shape.m
// HelloWorld
//
// Created by jimmy.yang on 11-1-26.
// Copyright 2011 __MyCompanyName__. All rights reserved.
//
#import "Shape.h"
@implementation Shape
- (void) setBounds:(ShapeRect)b
{
bounds = b;
}
- (void) setFillColor:(ShapeColor)f
{
fillColor =f;
}
//注：这个方法留给子类去实现，所以这里只要一个空壳就行了
- (void) draw
{
}
- (NSString*) getColorName:(ShapeColor)f
{
switch (f) {
case kRedColor:
return @"red";
break;
case kGreenColor:
return @"green";
break;
case kBlueColor:
return @"blue";
break;
default:
return @"no clue";
break;
}
}
@end
语法有点奇怪，初次接触，只能强迫自己忘记吧。
然后定义子类Circle
申明部分Circle.h
//
// Circle.h
// HelloWorld
//
// Created by jimmy.yang on 11-1-26.
// Copyright 2011 __MyCompanyName__. All rights reserved.
//
#import "Shape.h"
//注：因为Circle类不需要扩展其它方法，所以这里也只要一个空壳
@interface Circle : Shape {
}
@end
实现部分Circle.m
//
// Circle.m
// HelloWorld
//
// Created by jimmy.yang on 11-1-26.
// Copyright 2011 __MyCompanyName__. All rights reserved.
//
#import "Circle.h"
@implementation Circle
-(void) draw
{
NSLog(@"drawing a Cirle at (%d,%d,%d,%d) in %@",bounds.x,bounds.y,bounds.width,bounds.height,[super getColorName:fillColor]);
}
@end
注：上面展示了在obj-C中如何调用父类的方法[super getColorName:fillColor]
子类Rectangle
//
// Rectangle.h
// HelloWorld
//
// Created by jimmy.yang on 11-1-26.
// Copyright 2011 __MyCompanyName__. All rights reserved.
//
#import "Shape.h"
@interface Rectangle : Shape {
}
@end
实现部分
//
// Rectangle.m
// HelloWorld
//
// Created by jimmy.yang on 11-1-26.
// Copyright 2011 __MyCompanyName__. All rights reserved.
//
#import "Rectangle.h"
@implementation Rectangle
-(void) draw
{
NSLog(@"drawing a Rectangle at (%d,%d,%d,%d) in %@",bounds.x,bounds.y,bounds.width,bounds.height,[super getColorName:fillColor]);
}
@end
子类Ellipse
//
// Ellipse.h
// HelloWorld
//
// Created by jimmy.yang on 11-1-26.
// Copyright 2011 __MyCompanyName__. All rights reserved.
//
#import "Shape.h"
@interface Ellipse : Shape{
}
@end
实现部分
//
// Ellipse.m
// HelloWorld
//
// Created by jimmy.yang on 11-1-26.
// Copyright 2011 __MyCompanyName__. All rights reserved.
//
#import "Ellipse.h"
@implementation Ellipse
-(void) draw
{
NSLog(@"drawing a ellipse at (%d,%d,%d,%d) in %@",bounds.x,bounds.y,bounds.width,bounds.height,[super getColorName:fillColor]);
}
@end
最后看下调用的主函数HelloWorld.m
#import "CommDef.h"
#import "Circle.h"
#import "Rectangle.h"
#import "Ellipse.h"
int main (int argc, const char * argv[]) {
id shape[2] ;
ShapeRect rect0 = {0,0,10,30};
shape[0] = [Circle new];
[shape[0] setBounds:rect0];
[shape[0] setFillColor:kGreenColor];
[shape[0] draw];
ShapeRect rect1 = {0,0,40,50};
shape[1] = [Rectangle new];
[shape[1] setBounds:rect1];
[shape[1] setFillColor:kRedColor];
[shape[1] draw];
ShapeRect rect2 = {0,0,30,30};
shape[2] = [Ellipse new];
[shape[2] setBounds:rect2];
[shape[2] setFillColor:kBlueColor];
[shape[2] draw];
return 0;
}
注：上面的代码中有一个id的变量，在obj-C中id相当于“任意类型”，意为指向某对象的指针（哪怕你不知道这个对象是什么类型），总之，如果你不知道某对象的具体类型时，用它就对了。同时我们也看到了，创建一个类的实例用“[类 new]”来完成。
最后附上文件结构图:
