我如何正確使用NSString sizeWithFont constratinedToSize與NIAttributedLabel

我已經走過了什麼感覺就像這個方法在SO上的每一篇文章。很多海報的答案都是把一個非常大的值作爲高度限制。我如何正確使用NSString sizeWithFont constratinedToSize與NIAttributedLabel

但是，對我來說這是行不通的。這是我的代碼：

//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，認爲這不應該真的有效果，因爲該方法返回了我認爲是錯誤的大小是 NSString一部分。~~

~~我沒有蘋果的文檔中讀取的方法有時會截斷字符串，但我認爲多數民衆贊成在大高度約束是爲~~

編輯： 我發現它是一個問題NIAttributedLabel，如果我使用普通的UILabel，它可以很好地工作。這裏有兩個來源字符串和相應的截圖，第一表明我的問題，其他的決定是罰款：

"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?"

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"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