这有三个API都是新增的，标识有API_AVAILABLE(macosx(10.12), ios(10.0), watchos(3.0), tvos(10.0))。
.+ (NSTimer *)timerWithTimeInterval:(NSTimeInterval)interval repeats:(BOOL)repeats block:(void (^)(NSTimer *timer))block；
. + (NSTimer *)scheduledTimerWithTimeInterval:(NSTimeInterval)interval repeats:(BOOL)repeats block:(void (^)(NSTimer *timer))block；
.- (instancetype)initWithFireDate:(NSDate *)date interval:(NSTimeInterval)interval repeats:(BOOL)repeats block:(void (^)(NSTimer *timer))block；
特别是前两个，跟以下api一时手快容易混淆，容易让使用低于10.0系统的用户直接闪退,报错unrecognized selector;
.+ (NSTimer *)timerWithTimeInterval:(NSTimeInterval)ti invocation:(NSInvocation *)invocation repeats:(BOOL)yesOrNo;
.+ (NSTimer *)scheduledTimerWithTimeInterval:(NSTimeInterval)ti invocation:(NSInvocation *)invocation repeats:(BOOL)yesOrNo;
.+ (NSTimer *)timerWithTimeInterval:(NSTimeInterval)ti target:(id)aTarget selector:(SEL)aSelector userInfo:(nullable id)userInfo repeats:(BOOL)yesOrNo;
.+ (NSTimer *)scheduledTimerWithTimeInterval:(NSTimeInterval)ti target:(id)aTarget selector:(SEL)aSelector userInfo:(nullable id)userInfo repeats:(BOOL)yesOrNo;
