关于drawInRect: withAttributes: 等新方法的使用

新的方法采用的是 attributes，attributes参数需要的是一个数组
我们常用的有几个：

    NSMutableParagraphStyle* paragraphStyle = [[NSParagraphStyle defaultParagraphStyle] mutableCopy];
    paragraphStyle.lineBreakMode = NSLineBreakByCharWrapping;
    NSDictionary* dic = @{NSFontAttributeName:font,NSParagraphStyleAttributeName:paragraphStyle,NSForegroundColorAttributeName:[UIColor lightGrayColor]};

通过设置 NSParagraphStyleAttributeName，我们可以设置string的段落风格，比如 lineBreakMode
NSForegroundColorAttributeName 字体颜色
eg：
原先可以这样写：

CGSize size = [text sizeWithFont:font constrainedToSize:CGSizeMake(300, MAXFLOAT)lineBreakMode:NSLineBreakByCharWrapping];
[text drawInRect:CGRectMake(10,10,300, size.height) withFont:font lineBreakMode:NSLineBreakByCharWrapping];

iOS7 之后需要切换新方法，如下：

    NSMutableParagraphStyle* paragraphStyle = [[NSParagraphStyle defaultParagraphStyle] mutableCopy];
    paragraphStyle.lineBreakMode = NSLineBreakByCharWrapping;
    NSDictionary*attribute = @{NSFontAttributeName:font,NSParagraphStyleAttributeName:paragraphStyle};
    CGSize size = [text boundingRectWithSize:CGSizeMake(300, MAXFLOAT) options:NSStringDrawingUsesLineFragmentOrigin attributes:attribute context:nil].size;
    [text drawWithRect:CGRectMake(10, 10,300, size.height) options:NSStringDrawingUsesLineFragmentOrigin attributes:attribute context:nil];