iOS:(boundingRectWithSize)按大小计算字符串高度

    NSString *text = @"这里要很多字符，我就不打了……";
    NSAttributedString *attributeString = [[NSAttributedString alloc] initWithString:text attributes:attributes];
    NSRange range = NSMakeRange(0, attributeString.length);
    NSDictionary *dict = [attributeString attributesAtIndex:0 effectiveRange:&range];

    CGSize textSize = [text boundingRectWithSize:_contentTextView.bounds.size options:NSStringDrawingUsesLineFragmentOrigin| NSStringDrawingUsesFontLeading attributes:dict context:nil].size;

    NSLog(@"height ----> %f,width ----> %f", textSize.height, textSize.width);