问 将字符串写入NSPasteBoard

EN

我不能让这个方法返回YES：

- (BOOL) writeToPasteBoard:(NSString *)stringToWrite
    return [pasteBoard setString:stringToWrite forType:NSStringPboardType];
}

我已经验证了stringToWrite是正确的，这个方法总是返回NO。

有什么想法吗？

下面是这个类的其余部分：

@interface ClipBoard : NSObject {
    NSPasteboard *pasteBoard;
- (BOOL) writeToPasteBoard:(NSString *)stringToWrite;
- (NSString *) readFromPasteBoard;
@implementation ClipBoard
- (id) init
    [super init];
    pasteBoard = [NSPasteboard generalPasteboard];
    return self;
- (BOOL) writeToPasteBoard:(NSString *)stringToWrite
    return [pasteBoard setString:stringToWrite forType:NSStringPboardType];
- (NSString *) readFromPasteBoard