Objective c 如何限制NSTextField文本长度并始终保持大写？

需要一个文本限制为最多4个字符的NSTextField，并始终以大写形式显示，但无法找到一个实现此目标的好方法。我曾尝试通过绑定验证方法来实现这一点，但只有当控件失去第一响应程序时才会调用验证，这是不好的

暂时，我通过观察文本字段上的通知NSControlTextDidChangeNotification并让它调用以下方法使其工作：

- (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]];
  }
}

---

但这肯定不是最好的方法。有更好的建议吗？

您是否尝试附加自定义的

NSFormatter

子类？

Graham Lee建议的自定义NSFormatter是最好的方法

一个简单的难题是将视图控制器设置为文本字段的委托，然后只阻止任何涉及非大写或使长度超过4的编辑：

- (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;
}

---

我按照Graham Lee的建议做了，效果很好，下面是自定义格式化程序代码：

更新：添加了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

---

在上面我评论的例子中，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;
    }
}

改用这个（或类似的东西）：

这两种方法都是NSFormatter方法。第一个问题。假设您将文本输入限制为10个字符。如果在NSTEXT字段中逐个键入字符，它将正常工作，并防止用户超过10个字符

但是，如果用户将一个字符串粘贴到文本字段中，例如25个字符，则会发生如下情况：

1） 用户将粘贴到文本字段中

2） TextField将接受字符串

3） TextField将格式化程序应用于25长度字符串中的“最后一个”字符

4） 格式化程序将填充到25长度字符串中的“最后一个”字符，忽略其余字符

5） TextField将以25个字符结束，即使限制为10个字符

这是因为，我相信，第一种方法只适用于在NSTextField中键入的“最后一个字符”。上面显示的第二种方法适用于在NSTEXT字段中键入的“所有字符”。所以它对“粘贴”攻击免疫

---

我刚刚在尝试破解我的应用程序时发现了这个问题，我不是NSFormatter方面的专家，所以如果我错了，请纠正我。非常感谢您carlosb发布了这个示例。这帮了大忙！：）

这一实施采纳了上述几条建议。值得注意的是，它可以正确地处理不断更新的绑定

此外：

它正确地实现了粘贴

它包括一些关于如何在nib中有效使用该类的注释 没有进一步的子类化

守则：

@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

---

我需要一个格式化程序将Swift 4转换为大写。为了便于参考，我将其包括在这里：

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
    }
}

<代码>导入基础 类UppercaseFormatter:格式化程序{ 覆盖func字符串（对象：有？->字符串{ 如果let stringValue=obj as？字符串{ 返回stringValue.uppercased（） } 归零 } 重写func getObjectValue（j:autoreleasingusafmtablepointer？，对于字符串：string，errorDescription error:autoreleasingusafmtablepointer？）->Bool{ obj？.pointee=字符串作为任意对象 返回真值 } } 如果有人需要，快速回答

用法示例：

myTextField.formatter = CustomTextFieldFormatter(maxLength: 10, isUppercased: true)

---

class CustomTextFieldFormatter:格式化程序{
变量最大长度：UInt
变量大写：Bool
init（最大长度：UInt，大写：Bool）{
self.maxLength=maxLength
self.isUppercased=isUppercased
super.init（）
}
必需初始化？（编码器：NSCoder）{
fatalError（“初始化（编码者：）尚未实现”）
}
覆盖func字符串（对象：有？->字符串{
返回obj作为字符串
}
重写func getObjectValue（j:autoreleasingusafmtablepointer？，对于字符串：string，errorDescription error:autoreleasingusafmtablepointer？）->Bool{
obj？.pointee=字符串作为任意对象
返回真值
}
重写函数isPartialStringValid（uPartialStringPtr:AutoreleasingUnsafeMutablePointer，proposedSelectedRange proposedSelRangePtr:NSRangePointer？，OriginalStringOrigString:String，originalSelectedRange origSelRange:NSRange，错误描述错误：AutoreleasingUnsafeMutablePointer？->Bool{
如果partialStringPtr.pointee.length>maxLength{
返回错误
}
如果isUppercased&&partialStringPtr.pointee！=partialStringPtr.pointee.uppercased为NSString{
partialStringPtr.pointee=partialStringPtr.pointee.UPPERCASE为NSString
返回错误
}
返回真值
}
重写func attributedString（对于obj:Any，使用defaultattributes attrs:[NSAttributedString.Key:Any]？=nil）->NSAttributedString{
归零
}
}

你应该接受格雷厄姆的回答，因为他为你指明了正确的方向！干得好！感谢您抽出时间回来发布整个解决方案！我发现上面的代码有一个错误。使用isPartialStringValid:newEditingString:errorDescription:存在潜在的攻击。如果在键盘上逐个字符地将文本输入NSTEXT字段，则不会出现任何问题。但是，如果将包含2个或更多字符的字符串粘贴到文本字段中，它将对最后输入的字符执行验证，但忽略以前输入的所有字符。这可能导致在文本字段中插入的字符超过允许的数量。下面我将发布更多详细信息和解决方案（此处空间不足）。请您编辑“-init{”以读取“-（id）init{”？将使复制/粘贴更容易。请记住，如果您从Interface Builder将自定义格式设置程序拖到文本字段上，您将需要使用-（id）initWithCoder:（NSCoder*）aDecoder而不是

myTextField.formatter = CustomTextFieldFormatter(maxLength: 10, isUppercased: true)

class CustomTextFieldFormatter: Formatter {
    var maxLength: UInt
    var isUppercased: Bool
    
    init(maxLength: UInt, isUppercased: Bool) {
        self.maxLength = maxLength
        self.isUppercased = isUppercased
        super.init()
    }
    
    required init?(coder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
    
    override func string(for obj: Any?) -> String? {
        return obj as? String
    }
    
    override func getObjectValue(_ obj: AutoreleasingUnsafeMutablePointer<AnyObject?>?, for string: String, errorDescription error: AutoreleasingUnsafeMutablePointer<NSString?>?) -> Bool {
        obj?.pointee = string as AnyObject
        return true
    }
    
    override func isPartialStringValid(_ partialStringPtr: AutoreleasingUnsafeMutablePointer<NSString>, proposedSelectedRange proposedSelRangePtr: NSRangePointer?, originalString origString: String, originalSelectedRange origSelRange: NSRange, errorDescription error: AutoreleasingUnsafeMutablePointer<NSString?>?) -> Bool {
        
        if partialStringPtr.pointee.length > maxLength {
            return false
        }
        
        
        if isUppercased && partialStringPtr.pointee != partialStringPtr.pointee.uppercased as NSString {
            partialStringPtr.pointee = partialStringPtr.pointee.uppercased as NSString
            return false
        }
        
        return true
    }
    
    override func attributedString(for obj: Any, withDefaultAttributes attrs: [NSAttributedString.Key : Any]? = nil) -> NSAttributedString? {
        return nil
    }
}