iOS中，通常設置字體都是使用UIFont, 但是CATextLayer例外，詳細閱讀CATextLayer Class Reference，
May be either a CTFontRef, a
CGFontRef, an instance of
NSFont (Mac OS X only), or a string naming the font. In iOS, you cannot assign a
UIFont object to this property. Defaults to Helvetica.
The font property is only used when the string
property is not an NSAttributedString.
Note: If the font property is a CTFontRef, a
CGFontRef, or an instance of NSFont, the font size of the property is ignored.
設置CATextLayer字體：
錯誤： textLayer.font = [UIFont fontWithName:@"HiraKakuProN-W3" size:12];正確： textLayer.font = @"HiraKakuProN-W3"; textLayer.fontSize = 12;