在開發過程中一般會用到NSLog(<#NSString *format, ...#>)來獲得具體的資訊。

#ifdef DEBUG
#    define DLog(...) NSLog(__VA_ARGS__)
#else
#    define DLog(...) /* */
#endif
#define ALog(...) NSLog(__VA_ARGS__)
 

2.進入Xcode 4，選擇選單“Product”->“Manage Schemes”,選擇一個專案，點選“Edit”,Bulid Configuration

附： 檢查DEBUG標誌是否正確定義，xcode一般會在debug執行配置項裡面已經定義號了DEBUG標誌，如果沒定義我們就自己寫上，以我的xcode 4 為例，如下圖：

　　找到PreProcessor Macros 這個屬性，對於Debug配置我們給他寫上DEBUG，而在Release配置中把它留空。 這樣我們剛才那段預處理命令就可以根據這個標誌來判斷我們編譯的時除錯版本還是釋出版本，從而控制NSLog的輸出。 (因為xcode 4 會把debug/release 兩個配置項同時對比展現出來，而3.x版本的只能分別設定， 如果你用的時xcode 3.x 開發工具， 那麼就分別對Debug/Release 都檢查一下)。

NSLog() is a great tool that helps debugging efforts. Unfortunately it is expensive, especially on the iPhone, and depending on how it’s used or what you’re logging, it could leak sensitive or proprietary information. If you look around the web, you’ll find a few different ways to drop NSLog in your release builds. Here is what I’ve put together based on those.

First add the following to the <AppName>_Prefix.pch file in your Xcode project:

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#ifdef DEBUG
#    define DLog(...) NSLog(__VA_ARGS__)
#else
#    define DLog(...) /* */
#endif
#define ALog(...) NSLog(__VA_ARGS__)

Right-click on your target and click Get Info. Select the Build tab. Make sure Configuration is set to Debug. Add -DDEBUG to the Other C Flags of your target.

And that’s about it. When you want to log only in debug builds use DLog(). In release builds DLog() will be compiled as an empty comment. Otherwise use ALog() for logging in both debug and release builds. (A as in always.)

I like this approach for a few reasons:

1. Some approaches comment out all NSLog() statements when compiled. This approach lets me keep some logging if I want.
2. Using ALog() and DLog(), I make a conscious choice about which builds I’m going to log in.
3. There is very little setup.
4. There is no overhead. Because DLog() is defined as NSLog(), executing DLog() is no different than executing NSLog()

If you’d like to replace NSLog with DLog in your source files, here’s a quick sed command that you can run in Terminal:$ sed -i ".bak" 's/NSLog/DLog/' *.mFYI, this will make a backup of each of the .m files whether it changed them or not.