如何限制NSTextField文本长度并始终保持大写？

Question

需要具有最多4个字符的文本限制的NSTextField，并且始终以大写显示，但无法找出实现该目的的好方法。我试图通过绑定与验证方法来做到这一点，但验证只有在控件失去第一响应者时才会被调用，这是不好的。

即暂时我把它通过观察文本字段通知NSControlTextDidChangeNotification并让它调用该方法的工作：

- (void)textDidChange:(NSNotification*)notification { 
    NSTextField* textField = [notification object]; 
    NSString* value = [textField stringValue]; 
    if ([value length] > 4) { 
    [textField setStringValue:[[value uppercaseString] substringWithRange:NSMakeRange(0, 4)]]; 
    } else { 
    [textField setStringValue:[value uppercaseString]]; 
    } 
} 

但是，这肯定是不这样做的最佳方式。有什么更好的建议？

Answer 1

我一样格雷厄姆·李建议它工作正常，这里是自定义的格式化程序代码：

更新：添加了由Dave Gallagher报告的修复程序。谢谢！

@interface CustomTextFieldFormatter : NSFormatter { 
    int maxLength; 
} 
- (void)setMaximumLength:(int)len; 
- (int)maximumLength; 

@end 

@implementation CustomTextFieldFormatter 

- (id)init { 

    if(self = [super init]){ 

     maxLength = INT_MAX; 
    } 

    return self; 
} 

- (void)setMaximumLength:(int)len { 
    maxLength = len; 
} 

- (int)maximumLength { 
    return maxLength; 
} 

- (NSString *)stringForObjectValue:(id)object { 
    return (NSString *)object; 
} 

- (BOOL)getObjectValue:(id *)object forString:(NSString *)string errorDescription:(NSString **)error { 
    *object = string; 
    return YES; 
} 

- (BOOL)isPartialStringValid:(NSString **)partialStringPtr 
    proposedSelectedRange:(NSRangePointer)proposedSelRangePtr 
      originalString:(NSString *)origString 
    originalSelectedRange:(NSRange)origSelRange 
     errorDescription:(NSString **)error { 
    if ([*partialStringPtr length] > maxLength) { 
     return NO; 
    } 

    if (![*partialStringPtr isEqual:[*partialStringPtr uppercaseString]]) { 
     *partialStringPtr = [*partialStringPtr uppercaseString]; 
     return NO; 
    } 

    return YES; 
} 

- (NSAttributedString *)attributedStringForObjectValue:(id)anObject withDefaultAttributes:(NSDictionary *)attributes { 
    return nil; 
} 

@end 

Answer 2

您是否尝试过附加自定义NSFormatter子类？

Answer 3

格雷姆李建议的自定义NSFormatter是最好的方法。

一个简单的组装机将设置您的视图控制器作为文本字段的委托，然后只是阻止涉及非大写或做任何编辑长度超过4长：

- (BOOL)textField:(UITextField *)textField 
    shouldChangeCharactersInRange:(NSRange)range 
    replacementString:(NSString *)string 
{ 
    NSMutableString *newValue = [[textField.text mutableCopy] autorelease]; 
    [newValue replaceCharactersInRange:range withString:string]; 

    NSCharacterSet *nonUppercase = 
     [[NSCharacterSet uppercaseLetterCharacterSet] invertedSet]; 
    if ([newValue length] > 4 || 
     [newValue rangeOfCharacterFromSet:nonUppercase].location != 
      NSNotFound) 
    { 
     return NO; 
    } 

    return YES; 
} 

Answer 4

在我评论了上面的例子，这是不好的：

// Don't use: 
- (BOOL)isPartialStringValid:(NSString *)partialString 
      newEditingString:(NSString **)newString 
      errorDescription:(NSString **)error 
{ 
    if ((int)[partialString length] > maxLength) 
    { 
     *newString = nil; 
     return NO; 
    } 
} 

使用此（或类似的东西），而不是：

// Good to use: 
- (BOOL)isPartialStringValid:(NSString **)partialStringPtr 
     proposedSelectedRange:(NSRangePointer)proposedSelRangePtr 
       originalString:(NSString *)origString 
     originalSelectedRange:(NSRange)origSelRange 
      errorDescription:(NSString **)error 
{ 
    int size = [*partialStringPtr length]; 
    if (size > maxLength) 
    { 
     return NO; 
    } 
    return YES; 
} 

两者都是NSFormatter方法。第一个有问题。假设您将文本输入限制为10个字符。如果您将字符逐个输入到NSTextField中，它可以正常工作，并防止用户超过10个字符。

但是，如果用户是贴的，比如说一个字符串，25个字符的文本字段，会发生什么事情是这样的：

1）用户将其粘贴到文本字段

2）的TextField将接受的字符的字符串

3）的TextField将格式化应用到“最后”字符在25长度的字符串

4）格式化程序的东西“最后“字符在25长度的字符串，忽略其它

5）文本字段将结束它25个字符，即使它限制为10

这是因为，我相信，只有第一种方法适用于键入NSTextField的“最后一个字符”。上面显示的第二种方法适用于键入NSTextField的“所有字符”。所以它不受“粘贴”漏洞的影响。

我刚刚发现了这个问题，试图破坏我的应用程序，我不是NSFormatter的专家，所以如果我错了，请纠正我。非常感谢你carlosb张贴该示例。它帮助了很多！ :)

Answer 5

该实现采用了上述评论的几个建议。值得注意的是，它可以正确地连续更新绑定。

另外：

1. 它正确地实现糊。

2. 它包括一些笔记，关于如何在没有进一步子类化的情况下有效地在笔尖 中使用该类。

代码：

@interface BPPlainTextFormatter : NSFormatter { 
    NSInteger _maxLength; 
} 


/* 

Set the maximum string length. 

Note that to use this class within a Nib: 
1. Add an NSFormatter as a Custom Formatter. 
2. In the Identity inspector set the Class to BPPlainTextFormatter 
3. In user defined attributes add Key Path: maxLength Type: Number Value: 30 

Note that rather than attaching formatter instances to individual cells they 
can be positioned in the nib Objects section and referenced by numerous controls. 
A name, such as Plain Text Formatter 100, can be used to identify the formatters max length. 

*/ 
@property NSInteger maxLength; 

@end 


@implementation BPPlainTextFormatter 
@synthesize maxLength = _maxLength; 

- (id)init 
{ 
    if(self = [super init]){ 
     self.maxLength = INT_MAX; 
    } 

    return self; 
} 

- (id)initWithCoder:(NSCoder *)aDecoder 
{ 
    // support Nib based initialisation 
    self = [super initWithCoder:aDecoder]; 
    if (self) { 
     self.maxLength = INT_MAX; 
    } 

    return self; 
} 

#pragma mark - 
#pragma mark Textual Representation of Cell Content 

- (NSString *)stringForObjectValue:(id)object 
{ 
    NSString *stringValue = nil; 
    if ([object isKindOfClass:[NSString class]]) { 

     // A new NSString is perhaps not required here 
     // but generically a new object would be generated 
     stringValue = [NSString stringWithString:object]; 
    } 

    return stringValue; 
} 

#pragma mark - 
#pragma mark Object Equivalent to Textual Representation 

- (BOOL)getObjectValue:(id *)object forString:(NSString *)string errorDescription:(NSString **)error 
{ 
    BOOL valid = YES; 

    // Be sure to generate a new object here or binding woe ensues 
    // when continuously updating bindings are enabled. 
    *object = [NSString stringWithString:string]; 

    return valid; 
} 

#pragma mark - 
#pragma mark Dynamic Cell Editing 

- (BOOL)isPartialStringValid:(NSString **)partialStringPtr 
     proposedSelectedRange:(NSRangePointer)proposedSelRangePtr 
       originalString:(NSString *)origString 
     originalSelectedRange:(NSRange)origSelRange 
      errorDescription:(NSString **)error 
{ 
    BOOL valid = YES; 

    NSString *proposedString = *partialStringPtr; 
    if ([proposedString length] > self.maxLength) { 

     // The original string has been modified by one or more characters (via pasting). 
     // Either way compute how much of the proposed string can be accommodated. 
     NSInteger origLength = origString.length; 
     NSInteger insertLength = self.maxLength - origLength; 

     // If a range is selected then characters in that range will be removed 
     // so adjust the insert length accordingly 
     insertLength += origSelRange.length; 

     // Get the string components 
     NSString *prefix = [origString substringToIndex:origSelRange.location]; 
     NSString *suffix = [origString substringFromIndex:origSelRange.location + origSelRange.length]; 
     NSString *insert = [proposedString substringWithRange:NSMakeRange(origSelRange.location, insertLength)]; 

#ifdef _TRACE 

     NSLog(@"Original string: %@", origString); 
     NSLog(@"Original selection location: %u length %u", origSelRange.location, origSelRange.length); 

     NSLog(@"Proposed string: %@", proposedString); 
     NSLog(@"Proposed selection location: %u length %u", proposedSelRangePtr->location, proposedSelRangePtr->length); 

     NSLog(@"Prefix: %@", prefix); 
     NSLog(@"Suffix: %@", suffix); 
     NSLog(@"Insert: %@", insert); 
#endif 

     // Assemble the final string 
     *partialStringPtr = [[NSString stringWithFormat:@"%@%@%@", prefix, insert, suffix] uppercaseString]; 

     // Fix-up the proposed selection range 
     proposedSelRangePtr->location = origSelRange.location + insertLength; 
     proposedSelRangePtr->length = 0; 

#ifdef _TRACE 

     NSLog(@"Final string: %@", *partialStringPtr); 
     NSLog(@"Final selection location: %u length %u", proposedSelRangePtr->location, proposedSelRangePtr->length); 

#endif 
     valid = NO; 
    } 

    return valid; 
} 

@end 

Answer 6

我需要一个格式转换为大写的斯威夫特4.参考我在这里包括它：

import Foundation 

class UppercaseFormatter : Formatter { 

    override func string(for obj: Any?) -> String? { 
     if let stringValue = obj as? String { 
      return stringValue.uppercased() 
     } 
     return nil 
    } 

    override func getObjectValue(_ obj: AutoreleasingUnsafeMutablePointer<AnyObject?>?, for string: String, errorDescription error: AutoreleasingUnsafeMutablePointer<NSString?>?) -> Bool { 
     obj?.pointee = string as AnyObject 
     return true 
    } 
}