performSelector （选择器，用于消息传递）
前段时间在使用performSelector时出现了以下警告：performSelector may cause a leak because its selector is unknown，于是上网搜了一下资料，了解了一下performSelector这个东西。
先来看看关于performSelector的调用方法：
- (id)performSelector:(SEL)aSelector;
- (id)performSelector:(SEL)aSelector withObject:(id)object;
- (id)performSelector:(SEL)aSelector withObject:(id)object1 withObject:(id)object2;
以上三个方法只有参数不同，但最多只支持两个参数传递，当然多余的参数可以放到字典、数组里，这个不存在问题。
当调用我[target performSelector:action withObject:selfwithObject:arr];时，出现警告：performSelector may cause a leak because its selector is unknown，原因是arc下在编译期只确定消息名和参数数目,并不确定方法的地址，也不知道方法会返回什么，所以会出现警告。
解决办法：
1.宏定义忽略警告
#define SuppressPerformSelectorLeakWarning(Stuff) \
do { \
_Pragma("clang diagnostic push") \
_Pragma("clang diagnostic ignored \"-Warc-performSelector-leaks\"") \
Stuff; \
_Pragma("clang diagnostic pop") \
} while (0)
调用
SuppressPerformSelectorLeakWarning（
[target performSelector:action withObject:selfwithObject:arr];
）;
当然这只能忽略而已
2.延时调用，但是多线程中想过去maybe会出问题，没测过
[targetperformSelector:actionwithObject:selfafterDelay:1];
3.函数指针调用,符合oc底层调用
（stackoverflow：http://stackoverflow.com/questions/7017281/performselector-may-cause-a-leak-because-its-selector-is-unknown）
SELselector =NSSelectorFromString(@"someMethod");
((void(*)(id,SEL))[targetmethodForSelector:selector])(target, selector);
例如：((void(*)(id,SEL))[currentTargetmethodForSelector:currentAction])(message,currentAction);
