runtime关联属性

关联API介绍

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咱们先看看关联API，只有这三个API，使用也是很是简单的：

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/** * Sets an associated value for a given object using a given key and association policy. * * @param object The source object for the association. * @param key The key for the association. * @param value The value to associate with the key key for object. Pass nil to clear an existing association. * @param policy The policy for the association. For possible values, see “Associative Object Behaviors.” * * @see objc_setAssociatedObject * @see objc_removeAssociatedObjects */ void objc_setAssociatedObject ( id object , const void *key , id value , objc_AssociationPolicy policy )   /** * Returns the value associated with a given object for a given key. * * @param object The source object for the association. * @param key The key for the association. * * @return The value associated with the key \e key for \e object. * * @see objc_setAssociatedObject */ id objc_getAssociatedObject ( id object , const void *key )   /** * Removes all associations for a given object. * * @param object An object that maintains associated objects. * * @note The main purpose of this function is to make it easy to return an object *  to a "pristine state”. You should not use this function for general removal of *  associations from objects, since it also removes associations that other clients *  may have added to the object. Typically you should use \c objc_setAssociatedObject *  with a nil value to clear an association. * * @see objc_setAssociatedObject * @see objc_getAssociatedObject */ void objc_removeAssociatedObjects ( id object )

实际上，咱们几乎不会使用到objc_removeAssociatedObjects函数，这个函数的功能是移除指定的对象上全部的关联。

设置关联值

对于设置关联，咱们须要使用下面的API关联起来：

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void objc_setAssociatedObject ( id object , const void *key , id value , objc_AssociationPolicy policy )

参数说明：

• object：与谁关联，一般是传self
• key：惟一键，在获取值时经过该键获取，一般是使用static const void *来声明
• value：关联所设置的值
• policy：内存管理策略，好比使用copy

获取关联值

若是咱们要获取所关联的值，须要经过key来获取，调用以下函数：

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id objc_getAssociatedObject ( id object , const void *key )

参数说明：

• object：与谁关联，一般是传self，在设置关联时所指定的与哪一个对象关联的那个对象
• key：惟一键，在设置关联时所指定的键

关联策略

咱们先看看设置关联时所指定的policy，它是一个枚举类型，看官方说明：

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/** * Policies related to associative references. * These are options to objc_setAssociatedObject() */ typedef OBJC_ENUM ( uintptr_t , objc_AssociationPolicy ) {      OBJC_ASSOCIATION_ASSIGN = 0 ,            /**< Specifies a weak reference to the associated object. */      OBJC_ASSOCIATION_RETAIN_NONATOMIC = 1 , /**< Specifies a strong reference to the associated object.                                             *   The association is not made atomically. */      OBJC_ASSOCIATION_COPY_NONATOMIC = 3 ,    /**< Specifies that the associated object is copied.                                             *   The association is not made atomically. */      OBJC_ASSOCIATION_RETAIN = 01401 ,        /**< Specifies a strong reference to the associated object.                                             *   The association is made atomically. */      OBJC_ASSOCIATION_COPY = 01403            /**< Specifies that the associated object is copied.                                             *   The association is made atomically. */ } ;

咱们说明一下各个值的做用：

• OBJCASSOCIATIONASSIGN：表示弱引用关联，一般是基本数据类型，如int、float
• OBJCASSOCIATIONRETAIN_NONATOMIC：表示强（strong）引用关联对象
• OBJCASSOCIATIONCOPY_NONATOMIC：表示关联对象copy
• OBJCASSOCIATIONRETAIN：表示强（strong）引用关联对象，但不是线程安全的
• OBJCASSOCIATIONCOPY：表示关联对象copy，但不是线程安全的

扩展属性

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咱们来写一个例子，扩展UIControl添加Block版本的TouchUpInside事件。

扩展头文件声明：

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#import <UIKit/UIKit.h>   typedef void ( ^ HYBTouchUpBlock ) ( id sender ) ;   @interface UIControl ( HYBBlock )   @property ( nonatomic , copy ) HYBTouchUpBlock hyb_touchUpBlock ;   @end

扩展实现文件：

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#import "UIControl+HYBBlock.h" #import <objc/runtime.h>   static const void *sHYBUIControlTouchUpEventBlockKey = "sHYBUIControlTouchUpEventBlockKey" ;   @implementation UIControl ( HYBBlock )   - ( void ) setHyb_touchUpBlock : ( HYBTouchUpBlock ) hyb _ touchUpBlock {    objc_setAssociatedObject ( self ,                            sHYBUIControlTouchUpEventBlockKey ,                            hyb_touchUpBlock ,                            OBJC_ASSOCIATION_COPY ) ;       [ self removeTarget :self               action : @selector ( hybOnTouchUp : )     forControlEvents :UIControlEventTouchUpInside ] ;       if ( hyb_touchUpBlock ) {      [ self addTarget :self              action : @selector ( hybOnTouchUp : )    forControlEvents :UIControlEventTouchUpInside ] ;    } }   - ( HYBTouchUpBlock ) hyb _ touchUpBlock {    return objc_getAssociatedObject ( self , sHYBUIControlTouchUpEventBlockKey ) ; }   - ( void ) hybOnTouchUp : ( UIButton * ) sender {    HYBTouchUpBlock touchUp = self . hyb_touchUpBlock ;       if ( touchUp ) {      touchUp ( sender ) ;    } }   @end

使用起来很简单吧！！！

用法，在使用到的类进行 引用category；

   

UIButton *backBtn = [UIButton buttonWithType:UIButtonTypeCustom];

    [backBtn setHyb_touchUpBlock:^(id btn){

        NSLog(@"backk");

    }];

就这样愉快的使用啦