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)
     
    …
     
    @end

扩展：

    @imterface 也有类()
    {
        实例变量
    }
    //方法
     
    ...
     
    @end

 
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;
    @end
     
    #endif /* NSNumber_fk_h */


NSNumer+fk.m

    #import <Foundation/Foundation.h>
    #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)];
    }
    @end

 
MyApple.h

    #import <Foundation/Foundation.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;
    @end


MyApple.m

    #import "MyApple.h"
    //#import "MyApple+fk.h"
     
    #import <Foundation/Foundation.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");
    }
    @end


MyApple+fk.h

    #import "MyApple.h"
     
    #ifndef MyApple_fk_h
    #define MyApple_fk_h
    @interface MyApple(fk)
    -(void)test;
    @end
    #endif /* MyApple_fk_h */

 

main.h

 
    #import "MyApple.h"
    #import "NSNumber+fk.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
     
    #import <Foundation/Foundation.h>
    @interface Car : NSObject
    @property (nonatomic, copy) NSString *brand;
    @property (nonatomic, copy) NSString *model;
    -(void)drive;
    @end
    #endif /* Car_h */


Car+drive.h

    #import "Car.h"
    #ifndef Car_drive_h
    #define Car_drive_h
     
    @interface Car()
    @property (nonatomic, copy) NSString *color;
    -(void)drive:(NSString *)owner;
    @end
     
    #endif /* Car_drive_h */


Car.m

    #import <Foundation/Foundation.h>
    #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];
    }
    @end

main.m

    #import "Car+drive.h"
    int main(int argc, char * argv[]) {
        @autoreleasepool {
            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

 
 
作者：chen.yu
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