IOS学习笔记十二(类别和扩展)

1、类别(category)和扩展

类别:OC动态特征许使用类别添加新的方法，不需要创建子类

扩展：和类别相似，扩展相对于匿名类别

2、使用格式

类别：

@interface 已有类(类别名)

…

@end

@implmentaion 已有类(类别名)

扩展：

@imterface 也有类()

{

   实例变量

}

//方法

...

3、哪些功能

1)、给一个现成的类增加类别，然后实现其方法

2)、模块化设计

3)、调用私有方法（没有在接口部分定义而是在类实现部分定义的方法相对于私有方法，不许调用），通过定义向前引用，实现对私有方法调用

4、测试类别Demo

NSNumer+fk.h

#ifndef NSNumber_fk_h

#define NSNumber_fk_h

#import <Foundation/Foundation.h>

@interface NSNumber(fk)

-(NSNumber *)add:(double)num2;

-(NSNumber *)sub:(double)num2;

#endif /* NSNumber_fk_h */

NSNumer+fk.m

#import "NSNumber+fk.h"

@implementation NSNumber(fk)

-(NSNumber *)add:(double)num2

   return [NSNumber numberWithDouble:([self doubleValue] + num2)];

-(NSNumber *)sub:(double)num2

   return [NSNumber numberWithDouble:([self doubleValue] - num2)];

MyApple.h

#ifndef MyApple_h

#define MyApple_h

@interface MyApple : NSObject

@property (nonatomic, assign) double weight;

@property (nonatomic, copy) NSString *color;

//java方法构造方法一般没有返回，oc这里需要返回id,记住

-(id)initWithColor:(NSString *)color weight:(double)weight;

MyApple.m

#import "MyApple.h"

//#import "MyApple+fk.h"

@implementation MyApple

@synthesize color = _color;

@synthesize weight = _weight;

-(id)initWithColor:(NSString *)color weight:(double)weight

   if (self = [super init])

   {

       self.color = color;

       self.weight = weight;

   }

   return self;

-(NSString *) description

   return [NSString stringWithFormat:@"<MyApple[color=%@, weight=%g]>", self.color, self.weight];

-(void)test

   NSLog(@"this is test method");

MyApple+fk.h

#ifndef MyApple_fk_h

#define MyApple_fk_h

@interface MyApple(fk)

-(void)test;

#endif /* MyApple_fk_h */

main.h

#import "MyApple+fk.h"

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

   @autoreleasepool {

       NSNumber *num = [NSNumber numberWithDouble:3.5];

       NSLog(@"3.5 - 2 is %@", [num sub:2]);

       NSLog(@"3.5 + 2 is %@", [num add:2]);

       MyApple *apple = [[MyApple alloc] initWithColor:@"red" weight:5.6];

       NSLog(@"%@", apple);

       //No visible @interface for 'MyApple' declares the selector 'test'

       [apple test];

5、运行类别结果

3.5 - 2 is 1.5

3.5 + 2 is 5.5

<MyApple[color=red, weight=5.6]>

this is test method

6、测试扩展的Demo

Car.h

#ifndef Car_h

#define Car_h

@interface Car : NSObject

@property (nonatomic, copy) NSString *brand;

@property (nonatomic, copy) NSString *model;

-(void)drive;

#endif /* Car_h */

Car+drive.h

#import "Car.h"

#ifndef Car_drive_h

#define Car_drive_h

@interface Car()

-(void)drive:(NSString *)owner;

#endif /* Car_drive_h */

Car.m

#import "Car+drive.h"

@implementation Car

@synthesize brand;

@synthesize model;

@synthesize color;

-(void)drive

   NSLog(@"%@汽车正在路上奔驰",self);

-(void)drive:(NSString *)owner

   NSLog(@"%@正驾驶%@汽车在路上奔驰", owner, self);

-(NSString *)description

   return [NSString stringWithFormat:@"<Car [brand=%@, model=%@, color=%@]>", self.brand, self.model, self.color];

main.m

       Car *car = [Car new];

       car.brand = @"奔驰";

       car.model = @"S300";

       car.color = @"red";

       [car drive];

       [car drive:@"chenyu"];

7、运行扩展的结果

<Car [brand=奔驰, model=S300, color=red]>汽车正在路上奔驰

chenyu正驾驶<Car [brand=奔驰, model=S300, color=red]>汽车在路上奔驰