如何在NSString中反轉（顛倒）文本

Question

如何反轉iOS7中NSString變量的文本？ （我想顯示文字顛倒）。 注意：有很多解決方案將UILabel或UITextView顛倒過來，但這不是我想要的。

目前我能做到其中反轉串類別如下：

+ (NSString *)stringByReversingString:(NSString *)str 
{ 
char cString[150]; 
char revString[150]; 
NSString *retval; 
[str getCString:cString 
     maxLength:[str lengthOfBytesUsingEncoding:NSUTF8StringEncoding] + 1 
     encoding:NSUTF8StringEncoding]; 

for (int i = 0; i < strlen(cString); i++) { 
    revString[i] = cString[strlen(cString) - (i + 1)]; 
} 
revString[strlen(cString)] = '\0'; 
retval = [NSString stringWithCString:revString encoding:NSUTF8StringEncoding]; 

return retval; 
} 

但我怎麼會變成文字顛倒嗎？

Answer 1

您不能用純字符串轉換顯示一個顛倒的字符串，您有 來翻轉包含該字符串的視圖。

有一些 Unicode字符是「正常」的信件， 如

Ⅎ - TURNED CAPITAL F (U+2132) 

但不是所有字符顛倒版本。 你只能模擬天生通過使用一個表像http://www.fileformat.info/convert/text/upside-down-map.htm彈射：

uʍop-ǝpısdn sı ɹoʇıuoɯ ɹnoʎ uǝɥʇ sıɥʇ pɐǝɹ uɐɔ noʎ ɟI 

（創建使用http://www.fileformat.info/convert/text/upside-down.htm）

但需要注意的是一些字母只有一個非常粗略的顛倒近似， 如

K --> ⋊ - RIGHT NORMAL FACTOR SEMIDIRECT PRODUCT (U+22CA) 

和許多字符什麼也沒有。所以這適合一些有趣的顯示， 但不適用於生產應用程序。更好地翻轉視圖。

Answer 2

如果你想畫一個像這樣的字符串，子類NSLayoutManager和覆蓋-drawGlyphsForGlyphRange:atPoint:，在其中設置有CGAffineTransformMakeScale(-1, 1))發送-showCGGlyphs:positions:count:font:matrix:attributes:inContext:之前，在當前背景下的文本矩陣。 快速樣品重寫-drawGlyphsForGlyphRange:atPoint:繪製文本 「顛倒」，但不採取型動物的保健屬性，如下劃線，strikethoughs ...

@implementation ViewController 
- (void)viewDidLoad 
{ 
    [super viewDidLoad]; 
    // setup text objects 
    NSTextStorage *textStorage = [[NSTextStorage alloc] initWithString:[@"Lorem ipsum dolor sit er elit lamet, consectetaur cillium adipisicing pecu, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua." stringByReversingString]]; 

    MyLayoutManager *textLayout = [[MyLayoutManager alloc] init]; 

    [textStorage addLayoutManager:textLayout]; 

    NSTextContainer *textContainer = [[NSTextContainer alloc] initWithSize:self.view.bounds.size]; 

    [textLayout addTextContainer:textContainer]; 
    UITextView *textView = [[UITextView alloc] initWithFrame:CGRectMake(0,20,self.view.bounds.size.width,self.view.bounds.size.height-20) 
               textContainer:textContainer]; 
    [self.view addSubview:textView]; 
} 
@end 

@implementation MyLayoutManager 
- (void)drawGlyphsForGlyphRange:(NSRange)glyphsToShow atPoint:(CGPoint)origin 
{ 
    NSUInteger i; 
    CGContextRef ctx = UIGraphicsGetCurrentContext(); 
    NSRange lineRange; 

    for (i = glyphsToShow.location; i < NSMaxRange(glyphsToShow); i = NSMaxRange(lineRange)) 
    { 
     CGRect lineRect = [self lineFragmentRectForGlyphAtIndex:i effectiveRange:&lineRange]; 

     NSRange characterRange = [self characterRangeForGlyphRange:lineRange actualGlyphRange:NULL]; 

     /* This sample don't take care of different font attributes (size, etc ..) for the each lines */ 
     UIFont *font = [[self.textStorage attributesAtIndex:characterRange.location effectiveRange:NULL] objectForKey:NSFontAttributeName]; 
     UIColor *color = [[self.textStorage attributesAtIndex:characterRange.location effectiveRange:NULL] objectForKey:NSForegroundColorAttributeName]; 

     CGGlyph *glyphs = malloc(sizeof(CGGlyph) * lineRange.length); 
     CGSize *advances = malloc(sizeof(CGSize) * lineRange.length); 

     [self getGlyphsInRange:lineRange glyphs:glyphs properties:NULL characterIndexes:NULL bidiLevels:NULL]; 

     CTFontGetAdvancesForGlyphs((CTFontRef)font, kCTFontHorizontalOrientation, glyphs, advances, lineRange.length); 

     [color set]; 

     CGFontRef cgfont = CTFontCopyGraphicsFont((CTFontRef)font, NULL); 

     // setup CGContextRef to draw text "upside-down" 
     CGAffineTransform textMatrix = CGAffineTransformMakeScale(-1, 1); 
     CGContextSetFont(ctx, cgfont); 
     CGContextSetFontSize(ctx, [font pointSize]); 
     CGContextSetTextMatrix(ctx, textMatrix); 

     CGPoint position = lineRect.origin; 
     position.x += origin.x; 
     position.y += origin.y; 

     int j; 

     /* if you want the text to be right align, like the 'Lorem ipsum dolor' screenshot */ 
#if 1 
     position.x += lineRect.size.width; 
#else 
     /* if you want the text to be left align */ 
     for (j = 0; j < characterRange.length; j++) 
     { 
      position.x += advances[j].width; 
     } 
#endif 

     for (j = characterRange.length - 1; j >= 0; j--) 
     { 
      [self showCGGlyphs:&glyphs[j] positions:&position count:1 font:font matrix:textMatrix attributes:nil inContext:ctx]; 
      position.x -= advances[j].width; 
     } 

     CGFontRelease(cgfont); 

     free(glyphs); 
     free(advances); 
    } 
} 
@end