iOS

取经地址

1.使用关联##

关联是指把两个对象相互关联起来，使得其中的一个对象作为另一个对象的一部分。

使用关联，是基于关键字的，因此，我们可以为任意对象增加任意多的关联，但是关键字是唯一的。关联可以保证被关联对象在关联对象的整个生命周期都是可用的。

1.1 创建关联、获取被关联的关联对象、断开关联###

使用Objective-C中的runtime.h中

1. 创建关联：objc_setAssociatedObject函数

/** 
 * 使用给出的关键字和关联策略来设置对象的关联值
 * 
 * @param object       被关联对象、目标对象
 * @param key          关键字
 * @param value        关联对象，输入nil时候清除存在关联
 * @param policy       关联策略
 */
 void objc_setAssociatedObject(id object, const void *key, id value, objc_AssociationPolicy policy)

//*> objc_AssociationPolicy 关联策略枚举
typedef OBJC_ENUM(uintptr_t, objc_AssociationPolicy) {
    OBJC_ASSOCIATION_ASSIGN = 0,                   
    OBJC_ASSOCIATION_RETAIN_NONATOMIC = 1,
    OBJC_ASSOCIATION_COPY_NONATOMIC = 3,
    OBJC_ASSOCIATION_RETAIN = 01401,           
    OBJC_ASSOCIATION_COPY = 01403               
};

2）获取关联：objc_getAssociatedObject函数

/** 
 * 通过关键字返回被关联对象的关联值
 * 
 * @param object 被关联对象、目标对象
 * @param key     关键字
 * 
 * @return The value associated with the key e key for e object.
 */
 id objc_getAssociatedObject(id object, const void *key)

3）断开关联：objc_removeAssociatedObjects函数

/** 
 * 移除被关联对象的所有关联
 * 
 * @param object 被关联对象、目标对象
 * 
 * @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.
 */

备注：
1.关键字：void *类型，通常使用静态变量作为关键字，例如：
static const char *associatedKeyPanGesture = "__associated_key_pangesture";
2.关联策略：objc_AssociationPolicy枚举，和类声明中修饰属性的关键字一样。有assign和retain之分，有atomically和 no atomically之分。

1.2创建关联的测试代码###

static const char * associatedKeyMyname        = "_associated_key_myName";
static const char * associatiedKeyPersonalInfo = "_associated_key_personalinfomation";

//*> 关联对象
- (void)AssociationApiTest
{
    //*> 把array关联到tempstring - 观察作用域
    NSDictionary * infoDic  = @{@"Name":@"吕洪阳",@"Age":@"23",@"Gender":@"Male"};
    NSString     * infoNote = @"Personal information";
    objc_setAssociatedObject(infoNote, associatiedKeyPersonalInfo, infoDic, OBJC_ASSOCIATION_RETAIN);
    
    NSDictionary * associatedInfoDic   = (NSDictionary *)objc_getAssociatedObject(infoNote, associatiedKeyPersonalInfo);
    NSLog(@"
%@%@",infoNote,associatedInfoDic);
    
    //*> 把_myName关联到self - 观察作用域
    _myName = @"吕洪阳";
    objc_setAssociatedObject(self, associatedKeyMyname, _myName, OBJC_ASSOCIATION_RETAIN);

    NSNumber * associatedName1 = (NSNumber *)objc_getAssociatedObject(self, associatedKeyMyname);
    _myName = @"Steven Jobs";
    NSNumber * associatedName2 = (NSNumber *)objc_getAssociatedObject(self, associatedKeyMyname);
    
    NSLog(@"关联姓名之后：%@",associatedName1);
    NSLog(@"关联姓名修改：%@",associatedName2);//*> 关联的name没有因为关联对象的值而发成改变！
}

//*> 打印结果：
/*
2016-04-16 22:10:20.778 AssociatedDemo[2648:1100881] 
Personal information{
    Age = 23;
    Gender = Male;
    Name = "U5415U6d2aU9633";
}
2016-04-16 22:10:20.779 AssociatedDemo[2648:1100881] 关联姓名之后：吕洪阳
2016-04-16 22:10:20.779 AssociatedDemo[2648:1100881] 关联姓名修改：吕洪阳
*/

2.全屏滑动POP代码##

我的测试代码多多指教