iOS runtime基本用法

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一. 改變實(shí)例變量的值 (KVC/MJExtension都是通過這種方式來實(shí)現(xiàn)的)

• 添加Person類, 只添加了name屬性, 這里跳過實(shí)現(xiàn)文件

  @interface Person : NSObject
  
  @property (copy, nonatomic) NSString *name;
  
  @end
  

• 創(chuàng)建Person類型的實(shí)例對(duì)象

  self.person = [Person new];
  self.person.name = @"homer";
  NSLog(@"%@", self.person.name);
  

• 添加方法, 修改name屬性的值

  - (void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event {
      /// 獲取變量個(gè)數(shù)
      unsigned int count = 0;
      /// 獲取所有的實(shí)例變量
      Ivar *ivar = class_copyIvarList([self.person class], &count);
      /// 遍歷
      for (int i = 0; i < count; i++) {
          /// 實(shí)例變量
          Ivar var = ivar[i];
          /// 實(shí)例變量名字
          const char *varName = ivar_getName(var);
          /// 轉(zhuǎn)化一下
          NSString *name = [NSString stringWithUTF8String:varName];
          
          if ([name isEqualToString:@"_name"]) {
              object_setIvar(self.person, var, @"lynn");
              break;
          }
      }
      NSLog(@"%@", self.person.name);
  }
  

• 控制臺(tái)輸出,顯示修改成功

  [圖片上傳失敗...(image-da361-1523429930821)]

二. 方法交換(常用來hock/埋點(diǎn)等)

• 在Person中新增2個(gè)方法

  - (void)firstMethod {
      NSLog(@"1st method has been called");
  }
  
  - (void)secondMethod {
      NSLog(@"2nd method has been called");
  }
  

• 實(shí)現(xiàn)方法交換

  - (void)exchangeMethod {
      /// 獲取方法
      Method m1 = class_getInstanceMethod([self.person class], @selector(firstMethod));
      Method m2 = class_getInstanceMethod([self.person class], @selector(secondMethod));
      
      /// 交換方法
      method_exchangeImplementations(m1, m2);
  }
  

• 分別在交換前后調(diào)用firstMethod和secondMethod, 查看控制臺(tái)輸出

  [圖片上傳失敗...(image-a492d2-1523429930821)]

三. 動(dòng)態(tài)添加方法

• 添加方法

  - (void)addMethod {
      /// "v@:@"      v表示void, @表示id類型, :表示SEL
      class_addMethod([self.person class], @selector(run:), (IMP)run, "v@:@");
  }
  
  void run(id self, SEL _cmd, NSString *miles) {
      NSLog(@"Tome run %@ miles", miles);
  }
  
  - (void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event {
      [self addMethod];
      
      if ([self.person respondsToSelector:@selector(run:)]) {
          [self.person performSelector:@selector(run:) withObject:@"1"];
      } else {
          NSLog(@"Method named run: is not been defined!");
      }
  }
  

• 查看輸出

  [圖片上傳失敗...(image-9484c4-1523429930821)]

四. 使用關(guān)聯(lián)屬性給類型添加屬性

• 給Person類添加nick屬性

  @property (copy, nonatomic) NSString *name;
  
  - (void)firstMethod {
      NSLog(@"1st method has been called");
  }
  
  - (void)secondMethod {
      NSLog(@"2nd method has been called");
  }
  

• 調(diào)用屬性

  - (void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event {
      self.person.nick = @"Homer Lynn";
      NSLog(@"%@", self.person.nick);
  }
  

• 查看輸出

  [圖片上傳失敗...(image-7b5e8c-1523429930821)]