[IOS]label自适应高度换行

_wifi_analyzer_label.numberOfLines = 0;
_wifi_analyzer_label.lineBreakMode = NSLineBreakByWordWrapping;
CGSize size = [_wifi_analyzer_label sizeThatFits:CGSizeMake(_wifi_analyzer_label.frame.size.height, MAXFLOAT)];
CGRect frame = _wifi_analyzer_label.frame;
frame.size.height = size.height;
[_wifi_analyzer_label setFrame:frame];