iOS学习系列 - 扩展机制category与associative objc_setAssociatedObject
来源:互联网 发布:sql start with的意思 编辑:程序博客网 时间:2024/05/22 00:44
转自:http://www.cnblogs.com/liping13599168/archive/2012/09/13/2682664.html
category与associative作为objective-c的扩展机制的两个特性,category即类型,可以通过它来扩展方法;associative,可以通过它来扩展属性;在iOS开发中,可能category比较常见,相对的associative,就用的比较少,要用它必须使用<objc/runtime.h>的头文件,然后就可以自由使用objc_getAssociatedObject以及objc_setAssociatedObject,我们来看下这两个方法:
__OSX_AVAILABLE_STARTING(__MAC_10_6, __IPHONE_3_1);
OBJC_EXPORT id objc_getAssociatedObject(id object, const void *key)
__OSX_AVAILABLE_STARTING(__MAC_10_6, __IPHONE_3_1);
另外还有一个方法:
__OSX_AVAILABLE_STARTING(__MAC_10_6, __IPHONE_3_1);
objc_getAssociatedObject、objc_setAssociatedObject、objc_removeAssociatedObjects都是Obj-c中的外联方法,object 参数作为待扩展的对象实例,key作为该对象实例的属性的键,而value就是对象实例的属性的值,policy作为关联的策略,它的枚举包括:
OBJC_ASSOCIATION_ASSIGN = 0,
OBJC_ASSOCIATION_RETAIN_NONATOMIC = 1,
OBJC_ASSOCIATION_COPY_NONATOMIC = 3,
OBJC_ASSOCIATION_RETAIN = 01401,
OBJC_ASSOCIATION_COPY = 01403
};
具体我就多说了,可以看得懂的。
另外,objc_removeAssociatedObjects可以删除指定对象实例的所有扩展属性。
现在看一个简单的例子:(引用网上的例子:http://code4app.com/ios/Block-UI/504fe65d6803faa33f000003 )
这里,定义了一个"alert view"的按钮:
[viewController.view addSubview:button];
button.frame = CGRectMake(50, 50, 100, 44);
[button setTitle:@"alert view" forState:UIControlStateNormal];
现在对UIButton通过使用category对其进行方法扩展:
…...
- (void)handleControlEvent:(UIControlEvents)event withBlock:(void(^)(id sender))block {
NSString *methodName = [UIControl eventName:event];
NSMutableDictionary *opreations = (NSMutableDictionary*)objc_getAssociatedObject(self, &OperationKey);
if(opreations == nil)
{
opreations = [[NSMutableDictionary alloc] init];
objc_setAssociatedObject(self, &OperationKey, opreations, OBJC_ASSOCIATION_RETAIN);
}
[opreations setObject:block forKey:methodName];
[self addTarget:self action:NSSelectorFromString(methodName) forControlEvents:event];
}
objc_getAssociatedObject,objc_setAssociatedObject进行属性扩展:
OperationKey是一个字符类型,这里表示一个键,如果Opreations为空,会setAssociatedObject一个新的opreations对象到对应键的值中间。
addTarget:action:forControlEvents对于触摸事件进行目标绑定。
NSSelectorFromString(methodName) 将触发方法:
-(void)UIControlEventTouchDownRepeat{[self callActionBlock:UIControlEventTouchDownRepeat];}
-(void)UIControlEventTouchDragInside{[self callActionBlock:UIControlEventTouchDragInside];}
-(void)UIControlEventTouchDragOutside{[self callActionBlock:UIControlEventTouchDragOutside];}
-(void)UIControlEventTouchDragEnter{[self callActionBlock:UIControlEventTouchDragEnter];}
-(void)UIControlEventTouchDragExit{[self callActionBlock:UIControlEventTouchDragExit];}
-(void)UIControlEventTouchUpInside{[self callActionBlock:UIControlEventTouchUpInside];}
-(void)UIControlEventTouchUpOutside{[self callActionBlock:UIControlEventTouchUpOutside];}
-(void)UIControlEventTouchCancel{[self callActionBlock:UIControlEventTouchCancel];}
-(void)UIControlEventValueChanged{[self callActionBlock:UIControlEventValueChanged];}
-(void)UIControlEventEditingDidBegin{[self callActionBlock:UIControlEventEditingDidBegin];}
-(void)UIControlEventEditingChanged{[self callActionBlock:UIControlEventEditingChanged];}
-(void)UIControlEventEditingDidEnd{[self callActionBlock:UIControlEventEditingDidEnd];}
-(void)UIControlEventEditingDidEndOnExit{[self callActionBlock:UIControlEventEditingDidEndOnExit];}
-(void)UIControlEventAllTouchEvents{[self callActionBlock:UIControlEventAllTouchEvents];}
-(void)UIControlEventAllEditingEvents{[self callActionBlock:UIControlEventAllEditingEvents];}
-(void)UIControlEventApplicationReserved{[self callActionBlock:UIControlEventApplicationReserved];}
-(void)UIControlEventSystemReserved{[self callActionBlock:UIControlEventSystemReserved];}
-(void)UIControlEventAllEvents{[self callActionBlock:UIControlEventAllEvents];}
注意到这里会去执行callActionBlock:方法:
NSMutableDictionary *opreations = (NSMutableDictionary*)objc_getAssociatedObject(self, &OperationKey);
if(opreations == nil) return;
void(^block)(id sender) = [opreations objectForKey:[UIControl eventName:event]];
if (block) block(self);
}
最终会从扩展属性中得到^block,关于^block可以参考:http://blog.csdn.net/pjk1129/article/details/6577097
最后调用:
UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"alert"
message:nil
delegate:nil
cancelButtonTitle:@"ok"
otherButtonTitles:@"other",nil];
}];
点击按钮就会触发一个block函数。
这样就实现了objective-c的两种扩展机制。
- iOS学习系列 - 扩展机制category与associative objc_setAssociatedObject
- iOS学习系列 - 扩展机制category与associative
- iOS学习系列 - 扩展机制category与associative
- iOS学习系列 - 扩展机制category与associative
- iOS学习系列 - 扩展机制category与associative
- iOS学习系列 - 扩展机制category与associative
- iOS学习系列 - 扩展机制category与associative
- iOS学习系列 - 扩展机制category与associative
- iOS学习系列 - 扩展机制category与associative
- iOS学习之-扩展机制category与associative
- iOS 扩展机制category与associative
- iOS 扩展机制category与associative
- iOS 扩展机制category与associative
- iOS 扩展机制category与associative
- iOS扩展机制category与associative理解
- iOS 扩展机制category与associative
- iOS 扩展机制category与associative
- iOS 扩展机制category与associative
- 内网端口映射工具之80端口映射和全端口映射及辅助发布网站应用
- 图像处理基本概念——卷积,滤波,平滑
- Java接口与类集
- javaSE编程基础(函数)
- 更何况大家空间
- iOS学习系列 - 扩展机制category与associative objc_setAssociatedObject
- centos下firefox安装flash
- Error setting property values; nested exception is org.springframework.beans.NotWritablePropertyExce
- 最常用的两种C++序列化方案的使用心得(protobuf和boost serialization)
- POJ1151-(线段树扫描线+离散化)求矩形面积并
- pcDuino3 micro SD/TF 卡启动 (pcDuino3 Bootable SD )
- Scrum--迭代式增量软件开发
- 消息框MessageBox
- windows 8下VMWare创建MAC OS 虚拟机