objective-c - NSTokenField 委托(delegate)

Question

在 Apple 的“Cocoa token 字段编程指南”中的“与委托(delegate)的基本交互”部分中，当用户在 token 字段中键入一些文本时，委托(delegate)会收到 tokenField:completionsForSubstring:indexOfToken:indexOfSelectedItem:消息。

当用户键入时，标记字符委托(delegate)会收到 tokenField:representedObjectForEditingString: 消息。

因此，当我实现此方法时，它的行为方式非常不同。

这是我的委托(delegate)方法的实现:

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

NSLog(@"completionsForSubstring: %@", substring);
return [NSArray array];
}    

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

NSLog(@"representedObjectForEditingString: %@", editingString);
return editingString;
}

当我在 token 字段中输入“maksim”然后删除它时，会有一个日志:

2011-03-01 19:03:01.286 Aurum[23269:a0f] representedObjectForEditingString: m
2011-03-01 19:03:01.287 Aurum[23269:a0f] representedObjectForEditingString: m
2011-03-01 19:03:01.493 Aurum[23269:a0f] completionsForSubstring: m
2011-03-01 19:03:01.633 Aurum[23269:a0f] representedObjectForEditingString: ma
2011-03-01 19:03:01.633 Aurum[23269:a0f] representedObjectForEditingString: ma
2011-03-01 19:03:01.637 Aurum[23269:a0f] completionsForSubstring: ma
2011-03-01 19:03:03.737 Aurum[23269:a0f] representedObjectForEditingString: mak
2011-03-01 19:03:03.737 Aurum[23269:a0f] representedObjectForEditingString: mak
2011-03-01 19:03:03.741 Aurum[23269:a0f] completionsForSubstring: mak
2011-03-01 19:03:05.089 Aurum[23269:a0f] representedObjectForEditingString: maks
2011-03-01 19:03:05.089 Aurum[23269:a0f] representedObjectForEditingString: maks
2011-03-01 19:03:05.094 Aurum[23269:a0f] completionsForSubstring: maks
2011-03-01 19:03:05.841 Aurum[23269:a0f] representedObjectForEditingString: maksi
2011-03-01 19:03:05.841 Aurum[23269:a0f] representedObjectForEditingString: maksi
2011-03-01 19:03:05.845 Aurum[23269:a0f] completionsForSubstring: maksi
2011-03-01 19:03:06.697 Aurum[23269:a0f] representedObjectForEditingString: maksim
2011-03-01 19:03:06.697 Aurum[23269:a0f] representedObjectForEditingString: maksim
2011-03-01 19:03:06.701 Aurum[23269:a0f] completionsForSubstring: maksim
2011-03-01 19:03:12.353 Aurum[23269:a0f] representedObjectForEditingString: maksi
2011-03-01 19:03:12.354 Aurum[23269:a0f] representedObjectForEditingString: maksi
2011-03-01 19:03:12.853 Aurum[23269:a0f] representedObjectForEditingString: maks
2011-03-01 19:03:12.854 Aurum[23269:a0f] representedObjectForEditingString: maks
2011-03-01 19:03:12.936 Aurum[23269:a0f] representedObjectForEditingString: mak
2011-03-01 19:03:12.937 Aurum[23269:a0f] representedObjectForEditingString: mak
2011-03-01 19:03:13.020 Aurum[23269:a0f] representedObjectForEditingString: ma
2011-03-01 19:03:13.020 Aurum[23269:a0f] representedObjectForEditingString: ma
2011-03-01 19:03:13.103 Aurum[23269:a0f] representedObjectForEditingString: m
2011-03-01 19:03:13.104 Aurum[23269:a0f] representedObjectForEditingString: m

那么谁能解释一下出了什么问题以及为什么 token 字段表现得如此奇怪？

Answer 1

我只是尝试通过复制并粘贴您的代码来重现此问题。我得到:

2011-03-09 14:52:48.888 StackOverflowTesting[27789:a0f] completionsForSubstring: m
2011-03-09 14:52:49.242 StackOverflowTesting[27789:a0f] completionsForSubstring: ma
2011-03-09 14:52:49.560 StackOverflowTesting[27789:a0f] completionsForSubstring: mak
2011-03-09 14:52:49.911 StackOverflowTesting[27789:a0f] completionsForSubstring: maks
2011-03-09 14:52:50.017 StackOverflowTesting[27789:a0f] completionsForSubstring: maksi
2011-03-09 14:52:50.217 StackOverflowTesting[27789:a0f] completionsForSubstring: maksim
2011-03-09 14:52:50.647 StackOverflowTesting[27789:a0f] representedObjectForEditingString: maksim

这正是我所期望的输出。您是否更改了 NSTokenField 的默认标记字符？当您点击标记化字符时，它看起来不像标记化了 maksim(因为毕竟您可以逐个字符地删除它)。