ios UILabel 自動換行，縮小字型代碼

既可以自動換行，又可以根據字串的長度來調整字型的大小。

代碼：

_label = [ [ UILabel alloc ] initWithFrame: CGRectMake( 20 , 280 , 280 , 100 ) ];    _label.textAlignment = UITextAlignmentCenter;    _label.adjustsFontSizeToFitWidth = YES;    _label.minimumFontSize = 2;    _label.alpha = 0.4;    [ self.view addSubview: _label ];        // 文字    message = [ [ NSString alloc ] init ];    message = [ resultSet.resultDictionary objectForKey: @"saying" ];        CGFloat actualFontSize;    int numberOfLine = message.length / 23;    if ( !numberOfLine )    {        numberOfLine = 1;    }         [ message sizeWithFont: [ UIFont systemFontOfSize: 18 ] minFontSize: 6 actualFontSize: &actualFontSize forWidth: 300*numberOfLine lineBreakMode: NSLineBreakByWordWrapping ];    _label.text = message;    [ _label setFont: [ UIFont systemFontOfSize: actualFontSize  ] ];    _label.numberOfLines = numberOfLine + 1;