我如何正确使用NSString sizeWithFont constratinedToSize与NIAttributedLabel

我已经走过了什么感觉就像这个方法在SO上的每一篇文章。很多海报的答案都是把一个非常大的值作为高度限制。我如何正确使用NSString sizeWithFont constratinedToSize与NIAttributedLabel

但是，对我来说这是行不通的。这是我的代码：

//Create the contentLabel Label 
    CGSize size = [contentText sizeWithFont:[UIFont fontWithName:@"Helvetica" size:14] constrainedToSize:CGSizeMake(286, 9999) lineBreakMode:UILineBreakModeWordWrap]; 

    //Create the content label with its position 7 pixels below the title 
    contentLabel = [[NIAttributedLabel alloc] initWithFrame: 
        CGRectMake(7, titleContainerView.frame.origin.y + 7, 286, size.height)]; 

    //Set the provided text and the font 
    contentLabel.font = [UIFont fontWithName:@"Helvetica" size:14]; 
    contentLabel.numberOfLines = 0; 
    contentLabel.lineBreakMode = UILineBreakModeWordWrap; 
    contentLabel.text = contentText;

~~我使用 NIAttributedLabel，认为这不应该真的有效果，因为该方法返回了我认为是错误的大小是 NSString一部分。~~

~~我没有苹果的文档中读取的方法有时会截断字符串，但我认为多数民众赞成在大高度约束是为~~

编辑： 我发现它是一个问题NIAttributedLabel，如果我使用普通的UILabel，它可以很好地工作。这里有两个来源字符串和相应的截图，第一表明我的问题，其他的决定是罚款：

"Buying a Mobile\nHello - I'd like a Motorola Defy with a Smartphone 60 Plan.\nBroadband Problem\nMy Broadband’s out. I've tested the router and cables and ruled out my equipment. Is there a problem at your end?"

Screenshot 1

"Buying a Mobile\nI\'m Mrs Sina Manu-Harris. My account number is 156205169. I\'m going overseas in 6 months time on the 2nd of September and I\'d like to get organized in advance and buy a new mobile phone.\nBroadband Problem\nGood afternoon. It’s Mrs Sina Manu-Harris here. My account number is 156205169. My Broadband isn’t working. I’ve checked my network and phone cables and I've also checked my filters."

Screenshot 2