一个字符串展现多种字体、字号、字体大小（NSAttributedString）

NSAttributedString叫做富文本，是一种带有属性的字符串，通过它可以轻松的在一个字符串中表现出多种字体、字号、字体大小等各不相同的风格，还可以对段落进行格式化。

   以下是实现代码：

 UILabel *label = [[UILabel alloc] initWithFrame:CGRectMake(0, 0, 1000, 500)];
    label.numberOfLines = 0;//设置段落paragraphStyle，numberOfLines必须为0
    label.lineBreakMode = NSLineBreakByWordWrapping;
    label.backgroundColor = [UIColor redColor];
    
    NSString *str1 = @"全球开发者大会（WWDC）";
    NSString *str2 = @"美国在旧金山芳草地";
    NSString *str5 = @"太平洋时间";
    NSString *str3 = @"开始：2016-03-10";
    NSString *str4 = @"结束：2016-03-20";
    NSString *string = [NSString stringWithFormat:@"%@\n%@\n%@\n%@\n%@",str1,str2,str5,str3,str4];
    NSMutableAttributedString *attributedString = [[NSMutableAttributedString alloc] initWithString:string];
    NSMutableParagraphStyle *paragraphStyle = [[NSMutableParagraphStyle alloc] init];
    paragraphStyle.lineSpacing = 20.0;
    NSDictionary *attrsDictionary1 = @{NSFontAttributeName:[UIFont systemFontOfSize:30],
                                      NSParagraphStyleAttributeName:paragraphStyle};
    NSDictionary *attrsDictionary2 = @{NSParagraphStyleAttributeName:paragraphStyle};
    //给str1添加属性，字体加粗，并且设置段落间隙
    [attributedString addAttributes:attrsDictionary1 range:NSMakeRange(0, str1.length)];
    //给str2设置段落间隙
    [attributedString addAttributes:attrsDictionary2 range:NSMakeRange(str1.length, str2.length)];
    //attributedString如果还有别的样式需要添加可以这样依次加属性
    label.attributedText = attributedString;
    [self.view addSubview:label];