对字符串进行格式设置

需要对输出字符串设置格式，这样可以将URL和内容分开显示。请指教。

代码：NSLog(@"Description %@", string);

输出字符串：

2013-07-28 11:13:59.083 RSSreader[4915:c07] Description         
http://www.apple.com/pr/library/2013/07/23Apple-Reports-Third-Quarter-Results.html?sr=hotnews.rss
Apple today announced financial results for its fiscal 2013 third quarter ended
June     29, 2013. The Company posted quarterly revenue of $35.3 billion and quarterly 
net profit of $6.9 billion, or $7.47 per diluted share. 
Apple sold 31.2 million iPhones, which set a June quarter record. 

要格式化输出字符串，可以使用printf函数或者NSString的stringWithFormat方法。

例如，你可以使用以下代码来格式化输出字符串：

NSLog(@"URL: %@", urlString);
NSLog(@"Content: %@", contentString);

或者：

NSLog(@"URL: %@\nContent: %@", urlString, contentString);

或者：

NSString *formattedString = [NSString stringWithFormat:@"URL: %@\nContent: %@", urlString, contentString];
NSLog(@"%@", formattedString);

其中，%@是占位符，表示后面的字符串会替换占位符。

还有很多其他的占位符，比如%d表示整数，%f表示浮点数等。详情可以参考Apple的文档：String Format Specifiers。