计算NSAttributedString字符串size

/**
 *  return 动态返回字符串size大小
 *
 *  @param aString 字符串
 *  @param width   指定宽度
 *  @param height  指定宽度
 *
 *  @return CGSize
 */
- (CGSize)getStringRect:(NSAttributedString *)aString width:(CGFloat)width height:(CGFloat)height
{
    CGSize size = CGSizeZero;
    NSMutableAttributedString *atrString = [[NSMutableAttributedString alloc] initWithAttributedString:aString];
    NSRange range = NSMakeRange(0, atrString.length);
    
    //获取指定位置上的属性信息，并返回与指定位置属性相同并且连续的字符串的范围信息。
    NSDictionary* dic = [atrString attributesAtIndex:0 effectiveRange:&range];
    //不存在段落属性，则存入默认值
    NSMutableParagraphStyle *paragraphStyle = dic[NSParagraphStyleAttributeName];
    if (!paragraphStyle || nil == paragraphStyle) {
        paragraphStyle = [[NSParagraphStyle defaultParagraphStyle] mutableCopy];
        paragraphStyle.lineSpacing = 0.0;//增加行高
        paragraphStyle.headIndent = 0;//头部缩进，相当于左padding
        paragraphStyle.tailIndent = 0;//相当于右padding
        paragraphStyle.lineHeightMultiple = 0;//行间距是多少倍
        paragraphStyle.alignment = NSTextAlignmentLeft;//对齐方式
        paragraphStyle.firstLineHeadIndent = 0;//首行头缩进
        paragraphStyle.paragraphSpacing = 0;//段落后面的间距
        paragraphStyle.paragraphSpacingBefore = 0;//段落之前的间距
        [atrString addAttribute:NSParagraphStyleAttributeName value:paragraphStyle range:range];
    }
    
    //设置默认字体属性
    UIFont *font = dic[NSFontAttributeName];
    if (!font || nil == font) {
        font = [UIFont fontWithName:@"HelveticaNeue" size:12.0];
        [atrString addAttribute:NSFontAttributeName value:font range:range];
    }
    
    NSMutableDictionary *attDic = [NSMutableDictionary dictionaryWithDictionary:dic];
    [attDic setObject:font forKey:NSFontAttributeName];
    [attDic setObject:paragraphStyle forKey:NSParagraphStyleAttributeName];
    
    CGSize strSize = [[aString string] boundingRectWithSize:CGSizeMake(width, height)
                                                    options:NSStringDrawingUsesLineFragmentOrigin | NSStringDrawingUsesFontLeading
                                                 attributes:attDic
                                                    context:nil].size;
    
    size = CGSizeMake(strSize.width, strSize.height);
    return size;
}