错误：在NSTimer选择器中，ARC无法将Objective-C指针隐式转换为'SEL _Nonnull'

Question

我有这样的方法：

-(void)fastTapCartBack:(NSString*)ActionType

我想像这样在NSTimer中将其用作选择器：

self.timer = [NSTimer scheduledTimerWithTimeInterval:1 target:self selector:[self performSelector:@selector(fastTapCartBack:) withObject:@"FAST"] userInfo:nil repeats:NO]

但是有错误：

ARC不允许将Objective-C指针隐式转换为'SEL _Nonnull'

Answer 1

您正在传递一个方法调用[self performSelector:@selector(fastTapCartBack:) withObject:@"FAST"]作为选择器，Objective-C不允许这样做

取代这个

self.timer = [NSTimer scheduledTimerWithTimeInterval:1 target:self selector:[self performSelector:@selector(fastTapCartBack:) withObject:@"FAST"] userInfo:nil repeats:NO];

这样

您应该使用NSInvocation方式

NSMethodSignature * signature = [ViewController instanceMethodSignatureForSelector:@selector(fastTapCartBack:)];
NSInvocation * invocation = [NSInvocation
             invocationWithMethodSignature:signature];
[invocation setTarget:self];
[invocation setSelector:@selector(fastTapCartBack:)];
NSString * argument = @"FAST";
[invocation setArgument:&argument atIndex:2];

self.timer2 = [NSTimer scheduledTimerWithTimeInterval:1 invocation:invocation repeats:NO];

Answer 2

您无法在目标/操作模式中传递第二个参数。

但是，对于NSTimer有一个非常合适的解决方案， userInfo参数

self.timer = [NSTimer scheduledTimerWithTimeInterval:1 
                                              target:self 
                                            selector:@selector(fastTapCartBack:)
                                            userInfo:@"FAST" 
                                             repeats:NO];

并在选择器方法中获取信息

-(void)fastTapCartBack:(NSTimer *)timer {
     NSString *info = (NSString *)timer.userInfo;
}