IOS UILabel自适应里面的文字，自动调整宽度和高度的

UILabel *label = [[UILabel alloc] initWithFrame:CGRectMake(0,0,0,0)];//后面还会重新设置其size。
[label setNumberOfLines:0];
NSString *s = @"string......";
UIFont *font = [UIFont fontWithName:@"Arial" size:12];
CGSize size = CGSizeMake(320,2000);
CGSize labelsize = [s sizeWithFont:font constrainedToSize:sizelineBreakMode:UILineBreakModeWordWrap];
[label setFrame:CGRectMake(0, 0, labelsize.width, labelsize.height)];
[self.view addSubView:label];

引用：http://blog.sina.com.cn/s/blog_8988732e01010rvw.html