一、声明类接口步骤：

1、声明一个类接口，使用@interfacekeyword加上类名称。

2、用  { 实例变量 }  来定义各种数据成员。

3、方法声明，採用中缀符语法声明一个c函数，用到了冒号 ： 。

二、声明类接口实例：

//声明圆形circle类接口
@interface Circle : NSObject
{
    ShapeColor fillColor;//每次创建新的Circle对象后，对象中都包含这两个元素——类的实例变量
    ShapeRect   bounds;
}//指定实例变量

-(void) setFillColor: (ShapeColor) fillColor;//方法声明、中缀符
-(void) setBounds: (ShapeRect) bounds;
-(void) draw;

@end //Circle 完毕类的声明

三、实现类步骤

1、用keyword@implementation加上类名称

2、实现类中声明的方法，编写方法体 { 方法体 } 。

四、实现类实例

@implementation Circle//类实现

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

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

-(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 完毕类的实现

//
//  main.m
//  Shapes-Object
//
//  Created by jason on 14-6-10.
//  Copyright (c) 2014年 JasonApp. All rights reserved.
//

#import <Foundation/Foundation.h>

//定义形状的不同颜色
typedef enum{
    kRedColor,
    kGreenColor,
    kBlueColor
} ShapeColor;

//定义一个矩形来指定屏幕上的绘制区域
typedef struct{
    int x,y,width,height;
} ShapeRect;

//负责转换传入的颜色值，并返回NSString字面量
NSString *colorName(ShapeColor color)
{
    switch (color) {
        case kRedColor:
            return @"Red";
            break;
            
        case kGreenColor:
            return @"Green";
            break;
            
        case kBlueColor:
            return @"Blue";
            break;
    }
    
    return @"no clue";

}//colorName

//声明圆形circle类接口
@interface Circle : NSObject
{
    ShapeColor fillColor;//每次创建新的Circle对象后，对象中都包含这两个元素——类的实例变量
    ShapeRect   bounds;
}//指定实例变量

-(void) setFillColor: (ShapeColor) fillColor;//方法声明、中缀符
-(void) setBounds: (ShapeRect) bounds;
-(void) draw;

@end //Circle 完毕类的声明

@implementation Circle//类实现

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

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

-(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 完毕类的实现

//定义矩形
@interface Rectangle : NSObject
{
	ShapeColor	fillColor;
	ShapeRect	bounds;
}

- (void) setFillColor: (ShapeColor) fillColor;

- (void) setBounds: (ShapeRect) bounds;

- (void) draw;

@end // Rectangle


@implementation Rectangle

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


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


- (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

//定义OblateSphereoids
@interface OblateSphereoid : NSObject
{
	ShapeColor	fillColor;
	ShapeRect	bounds;
}

- (void) setFillColor: (ShapeColor) fillColor;

- (void) setBounds: (ShapeRect) bounds;

- (void) draw;

@end // OblateSphereoid


@implementation OblateSphereoid

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


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


- (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

//定义三角形
@interface Triangle : NSObject
{
	ShapeColor	fillColor;
	ShapeRect	bounds;
}

- (void) setFillColor: (ShapeColor) fillColor;

- (void) setBounds: (ShapeRect) bounds;

- (void) draw;

@end // Triangle


@implementation Triangle

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


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


- (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

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

int main(int argc, const char * argv[])
{

    id shapes[4];
	
	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 };
	shapes[3] = [Triangle new];
	[shapes[3] setBounds: rect3];
	[shapes[3] setFillColor: kRedColor];
	
	drawShapes (shapes, 4);
	
	return (0);
}

六、小结

1、过程式编程——“函数第一，数据第二”

2、OOP——“数据第一，函数第二”

3、“开放/关闭原则”——软件实体应该对拓展开放、对改动关闭

4、objective-c中不存在private方法

5、objective-c执行时负责执行重要的任务，比方对象发送消息和传递參数等，以支持应用程序的执行

6、实例化对象——向对应的类发送new消息来创建对象。