[轉]Xcode6中如何添加pch檔案

標籤：blog   http   io   ar   os   使用   sp   for   檔案   

在Xcode6之前，建立一個工程的時候，系統會幫我們自動建立一個以工程名為名字的pch (precompile header)檔案，在開發過程中，可以將那些整個工程都廣泛使用的標頭檔包含在該檔案下，編譯器就會自動的將pch檔案中的標頭檔添加到所有的源檔案中去，這樣在需要使用相關類的時候不需要使用import就可以直接使用標頭檔中的內容，很大程度上帶來了編程的便利性，但潛在的也帶來了一些問題，這也是在Xcode6中預設不再建立pch的原因吧。

關於pch的得與失，stackoverflow上有段話講的比較透徹：http://stackoverflow.com/questions/24158648/why-isnt-projectname-prefix-pch-created-automatically-in-xcode-6

 

As to where to put code that you would put in a prefix header, there is no code you should put in a prefix header. Put your imports into the files that need them. Put your definitions into their own files. Put your macros...nowhere. Stop writing macros unless there is no other way (such as when you need __FILE__). If you do need macros, put them in a header and include it.

The prefix header was necessary for things that are huge and used by nearly everything in the whole system (like Foundation.h). If you have something that huge and ubiquitous, you should rethink your architecture. Prefix headers make code reuse hard, and introduce subtle build problems if any of the files listed can change. Avoid them until you have a serious build time problem that you can demonstrate is dramatically improved with a prefix header.

In that case you can create one and pass it into clang, but it‘s incredibly rare that it‘s a good idea.

 

但有些時候，還是需要pch檔案的，那麼怎麼在Xcode6中添加一個pch檔案呢？

首先，Command+N，開啟建立檔案視窗：ios->other->PCH file，建立一個pch檔案，添加需要引入的標頭檔名：

 

 

其次，修改工程設定檔，將剛剛建立的PCH file的路徑添加到building setting中的precompile header選項中去，注意debug和release兩欄都要添加：

 

 

至此，大功告成，編譯一遍，新添加的pch檔案就可以正常使用了^_^。

轉載自：http://blog.csdn.net/lihuiqwertyuiop/article/details/39268101

[轉]Xcode6中如何添加pch檔案