UILabel根据字数多少自动实现适应高度

UILabel *msgLabel = [[UILabel alloc] initWithFrame:CGRectMake(15,45,0,0)]; //290 230
    msgLabel.backgroundColor = [UIColor lightTextColor];
    [msgLabel setNumberOfLines:0];
    msgLabel.lineBreakMode = UILineBreakModeWordWrap;
    UIFont *fonts = [UIFont fontWithName:@"Arial" size:12];
    msgLabel.font = fonts;
    CGSize size = CGSizeMake(290,1000);
    msgLabel.text = @"获取到的devicetoken，我们可以通过webservice服务提交给.net应用程序，这里我简单处理，直接打印出来，拷贝到.net应用环境中使用。";
    CGSize msgSie = [msgLabel.text sizeWithFont:fonts constrainedToSize:size lineBreakMode:UILineBreakModeWordWrap];
    [msgLabel setFrame:CGRectMake(15,290,msgSie.height)];