-（nullable id）performSelectorWithArgs:(SEL)sel, ...;
与- (void)performSelector:(SEL)sel afterDelay:(NSTimeInterval)delay;差不多
立即执行方法sel，使用如下：
1.无arg ：[view performSelectorWithArgs:@selector(removeFromSuperView)];
2.arg不是对象：[view performSelectorWithArgs:@selector(setCenter:),CGPointMake(0,0)];
3.arg是对象、且返回值是对象UIImage *image=[UIImage.class performSelectorWithArgs:@selector(imageWithData:sxale:),data,2.0];//这个好像运行不了
4.NSNumber *lengthValue=[@"hello" performSelectorWithArgs:@selector(length)];
NSUinteger length=lengthValue.unsignIntegerValue;
5.NSValue *frameValue=[view performSelectorWithArgs:@selector(frame)];
CGRect frame=frameValue.CGRectValue
ps.该方法在任何线程调用有效。与SEL sel的方法的线程是一致的
-（void）performSelectorWithArgs:(SEL)sel afterDelay:(NSTimeInterVal)delay,...;
过delay秒后执行sel，使用如下:
1.无arg [view performSelectorWithArgs:@selector(removeFromSuperView) afterDelay:2.0];
2.有arg [view performSelector:@selector(setCenter:) afterDelay:2.0,CGPointMake(0,0)];
这个可用于提交资料成功以后，过几秒推回上一个界面。
ps.该方法在子线程不起作用 ，要在主线程调用
-（nullable id）performSelectorWithArgsOnMainThred:@sel waitUntilDone:(BOOL)wait,...;
1.[view performSelectorWithArgsOnMainThread:@selector(removeFromSuperView), waitUntilDone:NO];
//variable arg is not object
2.[view performSelectorWithArgsOnMainThread:@selector(setCenter:), waitUntilDone:NO, CGPointMake(0, 0)];
wait,为no的时候表示异步操作。yes同步操作，要等Sel执行玩才进行下一步。
- (nullable id)performSelectorWithArgs:(SEL)sel onThread:(NSThread *)thread waitUntilDone:(BOOL)wait, ...;
thread 自己传，我测试子线程方法sel不走。待解决
- (void)performSelectorWithArgsInBackground:(SEL)sel, ...;
sel 在子线程运行
