Question

我正在尝试通过在respondsToSelector上运行[UIBarButtonItem appearance]来检测iOS 6特定的外观方法。但是，它始终为我返回NO，无论我指定哪个选择器：

// Should show NOPE in iOS 5, YEP in iOS 6. Shows NOPE always
NSLog(@"%@", [[UIBarButtonItem appearance] respondsToSelector:@selector(setBackgroundImage:forState:style:barMetrics:)] ? @"YEP" : @"NOPE"); 

// Should show YEP in both iOS 5 and iOS 6. Shows NOPE always
NSLog(@"%@", [[UIBarButtonItem appearance] respondsToSelector:@selector(setBackgroundImage:forState:barMetrics:)] ? @"YEP" : @"NOPE");

实际上使用这些方法在他们各自的iOS版本上运行良好，但我似乎无法检测到哪些可供我使用。那我该怎么做呢？

Answer 1

不要检查外观代理。你永远不能依赖它，因为它是一个代理。而是直接检查具有新方法的项目，在本例中为UIBarButtonItem：

BOOL hasNewMethod = [UIBarButtonItem instancesRespondToSelector:@selector(setBackgroundImage:forState:style:barMetrics:)];
if( hasNewMethod )
  NSLog(@"Running iOS 6 with new method");
else
  NSLog(@"Current OS doesn't support method...");

respondsToSelector因外观代理而失败

1 个答案: