問題描述

我正在嘗試通過在 [UIBarButtonItem 外觀] 上運行 respondsToSelector 來檢測 iOS 6 特定的外觀方法.但是，無論我指定什么選擇器，它總是為我返回 NO:

I’m trying to detect an iOS 6-specific appearance method, by running respondsToSelector on the [UIBarButtonItem appearance]. However, it always returns NO for me, whatever selector I specify:

// 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"); 

實際上，在它們各自的 iOS 版本上使用這些方法都可以正常工作，但我似乎無法檢測到哪一個對我可用.那么我該如何正確地做到這一點呢?

Actually using those methods works fine on their respective versions of iOS, but I can’t seem to detect which one is available to me. So how do I properly do that?

推薦答案

不要檢查外觀代理.你永遠不能依賴它，因為它是一個代理.相反，直接檢查具有新方法的項目，在這種情況下，UIBarButtonItem:

Don't check the appearance proxy. You can never rely on that, since it's a proxy. Instead, directly check the item that has the new method, in this case, the 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...");

這篇關于respondsToSelector 外觀代理失敗的文章就介紹到這了，希望我們推薦的答案對大家有所幫助，也希望大家多多支持html5模板網！