Correct use of the IOS development Pch file

Before Xcode6, create a new project Xcode automatically creates a "project name-prefix.pch" file under the supporting Files folder, which is also a header file, and the contents of the PCH header file can be shared and accessed by all other source files in the project. is a precompiled file.

First, let's talk about the role of PCH:

1, the storage of some global macro (the whole project is used in the macro);

2, used to include a number of all the header files (the entire project is used in the header file);

3, can automatically turn on or off the log output function.

How to add a PCH file in Xcode

In the project targets inside building setting search Prefix header, and then the Precompile Prefix header to the right of the no change to Yes

Then double-click on the right side of the Prefix header below the precompile Prefix header to add the project path to the PCH file you just created, adding the format: "$ (srcroot)/project name/PCH filename", $ (srcroot) The meaning of the project root directory. If you're not sure, you can right-click the PCH file and show in Finder:

The yellow circle comes out of $ (srcroot), which is the project root directory, and then there is a Pchtext and PCH two folders, so the path to the complete PCH file is: $ (srcroot)/pchtext/pch

Once added, he will automatically help you become the path where your project is located:

Yes, compile the program, if you have an error check the path you added is correct.

Precompile Prefix header is yes, pre-compiled PCH files are cached to improve compilation speed

Correct use of the IOS development Pch file