NSTextField, maximum string length, bindings and NSFormatter
NSTextField, maximum string length, bindings and NSFormatter
- Subject: NSTextField, maximum string length, bindings and NSFormatter
- From: "email@hidden" <email@hidden>
- Date: Thu, 24 Oct 2013 16:01:02 +0100
Have I missed something or is access to a decent NSFormatter subclass to handle NSTextField string length limiting troublesome?
There is some form on this:
http://stackoverflow.com/questions/827014/how-to-limit-nstextfield-text-length-and-keep-it-always-upper-case/827598#827598
http://www.cocoabuilder.com/archive/cocoa/184885-nsformatter-interfering-with-bindings-continuous-update.html
However the solutions provided have issues, some with bindings, and most suggestions don't handle pasted text well.
I am currently using the following. Comments, suggested improvements etc welcome.
Jonathan
@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
#define _TRACE
#import "BPPlainTextFormatter.h"
@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];
// 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;
}
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