NSTokenField不可编辑

Question

我有一个NSTokenField，不会让我编辑它。不可编辑，我的意思是它被卡在占位符文本上并点击它不允许我输入它。有谁知道为什么会这样？

为了澄清，这是我的委托代码。我将NSTokenField连接到IBOutlet，并将令牌字段连接到InputFieldDelegate对象（蓝盒事物）。

InputFieldDelegate.h：

    @interface InputFieldDelegate : NSObject <NSTokenFieldDelegate> {

    NSTokenField *inputTokenField;
}
@property (assign) IBOutlet NSTokenField *inputTokenField;

- (NSArray *)tokenField:(NSTokenField *)tokenFieldArg 
completionsForSubstring:(NSString *)substring 
           indexOfToken:(NSInteger)tokenIndex 
    indexOfSelectedItem:(NSInteger *)selectedIndex;
- (id)tokenField:(NSTokenField *)tokenField
representedObjectForEditingString:(NSString *)editingString;

@end

InputFieldDelegate.m：

#import "InputFieldDelegate.h"

@implementation InputFieldDelegate
@synthesize inputTokenField;

- (void)applicationDidFinishLaunching:(NSNotification *)aNotification
{
    inputTokenField = [[NSTokenField alloc] init];
    [inputTokenField setDelegate:self];
}

- (NSArray *)tokenField:(NSTokenField *)tokenFieldArg 
completionsForSubstring:(NSString *)substring 
           indexOfToken:(NSInteger)tokenIndex 
    indexOfSelectedItem:(NSInteger *)selectedIndex {

    return [NSArray arrayWithObject: nil];
}

- (id)tokenField:(NSTokenField *)tokenField
representedObjectForEditingString:(NSString *)editingString {
    return editingString;
}

@end