cannot find protocol declaration for "RefreshAudioListViewDelegate"

今天一個很變態的問題卡住了：cannot find protocol declaration for "RefreshAudioListViewDelegate"

1.在PlayerController.h自定義了 一個代理 RefreshAudioListViewDelegate

#import "PlayerListViewController.h"
@protocol RefreshAudioListViewDelegate <NSObject>
- (void) updateCurrentPlayedAudio:(NSUInteger) currentPlayedIndex;
@end

@interface PlayerController : NSObject

2.在PlayerListViewController.h中

#import "PlayerController.h"

@class PlayerController;
@interface PlayerListViewController : UIViewController< RefreshAudioListViewDelegate>
{
    PlayerController                 *playerController;
}

編譯器提示“cannot find protocol declaration for "RefreshAudioListViewDelegate”

分析原因：

在編譯器編譯順序：

1.PlayerListViewController.h文件時，首先發現#import "PlayerController.h",編譯器會跑到PlayerController.h中。

2.在PlayerController.h中首先發現#import "PlayerListViewController.h"，編譯器又會到PlayerListViewController中加載內容。

3.這時 當見到

@interface PlayerListViewController : UIViewController< RefreshAudioListViewDelegate>這一句的時候，由於在PlayerController中定義代理的語句還沒有加載，所以編譯器會報錯：

cannot find protocol declaration for "RefreshAudioListViewDelegate"

解決辦法：

刪除PlayerController.h中的

#import "PlayerListViewController.h"