您的问题对我很感兴趣。所以在几个小时内我就提出了解决方案。它远非完美，但您可以使用它并修复剩余的错误。
这是一个带文本视图的简单视图控制器。您可以添加输入文本的文本，也可以使用

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;

所以这是代码：

ReverseTextVC.h

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

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

希望它可以帮助你=）

Hope it helps you =)