Object-C 开发(一、代码规则)

不写过多文字，直接上代码表示

 

一、Interface 定义

 

 @interface Circle : NSObject
{
ShapeColor fillColor;
ShapeRect bounds;
}
- (void) setFillColor: (ShapeColor) fillColor;
- (void) setBounds: (ShapeRect) bounds;
- (void) draw;
@end // Circle

 

 

二、Circle实现

 

@implementation Circle
- (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

 

三、相同可以用相同的方法实现：OblateSphereoid 和 Rectangle

四、使用方法:

 

int main (int argc, const char * argv[])
{
id shapes[3];
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];
drawShapes (shapes, 3);
return (0);
} // main

 

五、派生

 

对于各种形状的  setFillColor 和 setBounds 是重复代码。

 

@interface Shape : NSObject
{
ShapeColor fillColor;
ShapeRect bounds;
}
- (void) setFillColor: (ShapeColor) fillColor;
- (void) setBounds: (ShapeRect) bounds;
- (void) draw;
@end // Shape

 

实现Shape.
@implementation Shape
- (void) setFillColor: (ShapeColor) c
{
fillColor = c;
} // setFillColor
- (void) setBounds: (ShapeRect) b
{
bounds = b;
} // setBounds
- (void) draw
{
} // draw
@end // Shape

 

实现 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

 

实现 Rectangle

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

 

六、函数重载

 

Circle 要改变 setFillColor 行为

 

@implementation Circle
- (void) setFillColor: (ShapeColor) c
{
if (c == kRedColor) {
c = kGreenColor;
}
[super setFillColor: c];
} // setFillColor
// 其它Circle 部分代码不变

@end // Circle

 

 七、组合

Class tire

 

@interface Tire : NSObject
@end // Tire
@implementation Tire
- (NSString *) description
{
return (@"I am a tire. I last a while");
} // description
@end // Tire

 

 

Class Engine

 

@interface Engine : NSObject
@end // Engine
@implementation Engine
- (NSString *) description
{
return (@"I am an engine. Vrooom!");
} // description
@end // Engine

 

 

@interface Car : NSObject
{
Engine *engine;
Tire *tires[4];
}
- (void) print;
@end // Car

 

 

@implementation Car
- (id) init
{

//一种 Object-C 通用的初始化方法
if (self = [super init]) {
engine = [Engine new];
tires[0] = [Tire new];
tires[1] = [Tire new];
tires[2] = [Tire new];
tires[3] = [Tire new];
}
return (self);
} // init 

 

 

- (void) print
{
NSLog (@"%@", engine);
NSLog (@"%@", tires[0]);
NSLog (@"%@", tires[1]);
NSLog (@"%@", tires[2]);
NSLog (@"%@", tires[3]);
} // print
@end // Car

 

 

int main (int argc, const char * argv[])
{
Car *car;
car = [Car new];
[car print];
return (0);
} // main

Result:

 

I am an engine. Vrooom!
I am a tire. I last a while.
I am a tire. I last a while.
I am a tire. I last a while.
I am a tire. I last a while.

八、getter 和 setter

@interface Car : NSObject
{
 Engine *engine;
 Tire *tires[4];
}

//注意：对于 getter 方法不使用getEngie 的命令方式，而是直接使用 engine.
//get 在 Cocoa 中有特殊含义，
//The word “get” has a special meaning in Cocoa: in a Cocoa method name, it means the method returns a value via a pointer that you pass in as a parameter.
- (Engine *) engine;
- (void) setEngine: (Engine *) newEngine;
- (Tire *) tireAtIndex: (int) index;
- (void) setTire: (Tire *) tire
  atIndex: (int) index;
- (void) print;
@end // Car

@implement
- (Engine *) engine
{
return (engine);
} // engine
- (void) setEngine: (Engine *) newEngine
{
engine = newEngine;
} // setEngine

- (void) setTire: (Tire *) tire
atIndex: (int) index
{
 if (index < 0 || index > 3) {
  NSLog (@"bad index (%d) in setTire:atIndex:", index);
  exit (1);
 }
 tires[index] = tire;
} // setTire:atIndex:

- (Tire *) tireAtIndex: (int) index
{
 if (index < 0 || index > 3) {
  NSLog (@"bad index (%d) in "tireAtIndex:",index);
  exit (1);
 }
 return (tires[index]);
} // tireAtIndex
@end

int main (int argc, const char * argv[])
{
 Car *car = [Car new];
 Engine *engine = [Engine new];
 [car setEngine: engine];

 int i;
 for (i = 0; i < 4; i++) {
  Tire *tire = [Tire new];
  [car setTire: tire atIndex: i];
 }
 [car print];
 return (0);
} // main

//输出
I am an engine. Vrooom!
I am a tire. I last a while.
I am a tire. I last a while.
I am a tire. I last a while.
I am a tire. I last a while.

 九、扩展

@interface Slant6 : Engine
@end // Slant6
@implementation Slant6
- (NSString *) description
{
 return (@"I am a slant- 6. VROOOM!");
} // description
@end // Slant6

@interface AllWeatherRadial : Tire
@end // AllWeatherRadial
@implementation AllWeatherRadial
- (NSString *) description
{
 return (@"I am a tire for rain or shine.");
} // description
@end // AllWeatherRadial

int main (int argc, const char * argv[])
{
 Car *car = [Car new];
 int i;
 for (i = 0; i < 4; i++) {
  Tire *tire = [AllWeatherRadial new];
  [car setTire: tire
   atIndex: i];
 }
 Engine *engine = [Slant6 new];
 [car setEngine: engine];
 [car print];
 return (0);
} // main

 

 

Composition or Inheritance?

Composition = has a; Inheritance = is a.