//初始化label 

UILabel *label = [[UILabel alloc] initWithFrame:CGRectMake(0,0,0,0)];

//設置自動行數與字符換行

[label setNumberOfLines:0]; 

label.lineBreakMode = UILineBreakModeWordWrap;  

// 測試字串   NSString *s = @"這是一個測試！！！";

  UIFont *font = [UIFont fontWithName:@"Arial" size:12];

  //設置一個行高上限

CGSize size = CGSizeMake(320,2000);

//計算實際frame大小，並將label的frame變成實際大小   CGSize labelsize = [s sizeWithFont:font constrainedToSize:size lineBreakMode:UILineBreakModeWordWrap];  [label setFrame:CGRectMake:(0,0, labelsize.width, labelsize.height)];