該實現採用了上述評論的幾個建議。值得注意的是，它可以正確地連續更新綁定。
另外：
它正確地實現糊。
它包括一些筆記，關於如何在沒有進一步子類化的情況下有效地在筆尖 中使用該類。
代碼：
@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
你應該接受Grahams的回答，因爲他指出你的方向正確！好工作壽！ – Jab
感謝您花時間回來發佈整個解決方案！ –
我發現上面的代碼有錯誤。有一個潛在的利用isPartialStringValid：newEditingString：errorDescription :.如果您在鍵盤上逐字輸入文本到NSTextField中，則不會出現問題。但是，如果您將一個包含2個或更多字符的字符串粘貼到文本字段中，它將對輸入的最後一個字符執行驗證，但忽略所有先前輸入的字符。這可能會導致插入更多字符而不允許插入到文本字段中。 下面我會發布更多的細節和解決方案（空間不足）。 –