You question have really interested me. So in a matter of hour I've came up with solution. It is far from perfect, but you can use it and fix remaining bugs.
This is a simple view controller with text view. You can add text typing it or you can set the value using
-(void) setText:(NSString*) txt;
So here is the code:
ReverseTextVC.h
@interface ReverseTextVC : UIViewController <UITextViewDelegate> {
NSMutableArray* _lines;
UITextView* _tv;
}
/**
Returns reversed text.
The lines is also updated. This array contains all lines. You should pass this array again if you want to append the text.
*/
+(NSString*) reverseText:(NSString*) text withFont:(UIFont*) font carretPosition:(NSRange*) cpos Lines:(NSMutableArray*) lines Bounds:(CGRect) bounds;
-(void) setText:(NSString*) txt;
@end
ReverseTextVC.m
@implementation ReverseTextVC
-(id) init {
if( self = [super init] ) {
_tv = [[UITextView alloc] initWithFrame: CGRectMake(0, 0, 320, 480)];
_tv.textAlignment = UITextAlignmentRight;
_tv.delegate = self;
[self.view addSubview: _tv];
[_tv release];
_lines = [[NSMutableArray alloc] initWithCapacity: 10];
[_lines addObject: [NSMutableString stringWithCapacity: 255]];
}
return self;
}
-(void) dealloc {
[_lines release];
[super dealloc];
}
-(void) loadView {
UIView* v = [[UIView alloc] initWithFrame: CGRectMake(0, 20, 320, 480)];
self.view = v;
[v release];
}
-(void) setText:(NSString*) txt {
NSString* result = nil;
NSRange rng;
NSArray* words = [txt componentsSeparatedByString: @" "];
//we should do it iteratively (cause it's the simplest way =) )
for(NSString* word in words) {
word = [NSString stringWithFormat: @"%@ ", word];
for(int i=0; i<[word length]; ++i) {
NSRange r; r.length = 1; r.location = i;
result = [ReverseTextVC reverseText: [word substringWithRange: r]
withFont: _tv.font
carretPosition: &rng
Lines: _lines
Bounds: _tv.bounds];
}
}
_tv.text = result;
}
#pragma mark -
#pragma mark UITextViewDelegate
-(BOOL) textView:(UITextView*) textView shouldChangeTextInRange:(NSRange) range replacementText:(NSString*) text {
NSRange rng;
textView.text = [ReverseTextVC reverseText: text
withFont: textView.font
carretPosition: &rng
Lines: _lines
Bounds: textView.bounds];
textView.selectedRange = rng;
return NO;
}
#pragma mark -
#pragma mark Static
+(NSString*) reverseText:(NSString*) text withFont:(UIFont*) font carretPosition:(NSRange*) cpos Lines:(NSMutableArray*) lines Bounds:(CGRect) bounds {
cpos->length = 0;
cpos->location = 0;
if( [text length] ) {
if( ![text isEqualToString: @"\n"] ) {
[(NSMutableString*)[lines lastObject] insertString: text
atIndex: 0];
} else {
[lines addObject: [NSMutableString stringWithCapacity: 255]];
}
} else {
//backspace
//TODO:
NSRange del_rng;
del_rng.length = 1;
del_rng.location = 0;
if( [(NSMutableString*)[lines lastObject] length] ) {
[(NSMutableString*)[lines lastObject] deleteCharactersInRange: del_rng];
}
if( ![(NSMutableString*)[lines lastObject] length] ) {
[lines removeLastObject];
}
}
CGSize sz = [(NSString*)[lines lastObject] sizeWithFont: font];
if( sz.width >= bounds.size.width-15 ) {
NSMutableArray* words = [NSMutableArray arrayWithArray: [(NSString*)[lines lastObject] componentsSeparatedByString: @" "]];
NSString* first_word = [words objectAtIndex: 0];
[words removeObjectAtIndex: 0];
[(NSMutableString*)[lines lastObject] setString: [words componentsJoinedByString: @" "]];
[lines addObject: [NSMutableString stringWithString: first_word]];
}
NSMutableString* txt = [NSMutableString stringWithCapacity: 100];
for(int i=0; i<[lines count]; ++i) {
NSString* line = [lines objectAtIndex: i];
if( i<([lines count]-1) ) {
[txt appendFormat: @"%@\n", line];
cpos->location += [line length]+1;
} else {
[txt appendFormat: @"%@", line];
}
}
return txt;
}
@end
Hope it helps you =)