In the previous versions of Xcode, a PCH file will be automatically added into your project upon creation. A PCH (precompiled header) file enables you to import certain headers into all your classes, so that you do not have to manually add them into all of them. This saves a lot of hassle and creates cleaner code (it can also save build time). I have to caution though, that we have to avoid importing ALL header files into ALL classes.

I create a Constants.h file to store my number and string constants for use in my classes, so I have to import it into almost every class. In this case, a PCH file will come in good use.

First, go to File > New > File...:

On the left pane, select Other under iOS. Select PCH File on the right pane.

Save your file in your project folder (let’s say your file name is “MyPrefixHeader.pch”).

Next, go to your Target’s Build Settings.

• Change the value in Prefix Header to the location of your PCH file (e.g. my project folder is Luvelle Codes, so the location of my PCH file is Luvelle Codes/MyPrefixHeader.pch).
• Also change the value in Precompile Prefix Header to YES.

Now, add import statements into your PCH file!

//
//  PrefixHeader.pch
//  Luvelle Codes
//
//  Created by Michelle Teo on 12/1/15.
//  Copyright (c) 2015 Michelle Teo. All rights reserved.
//

#ifndef Luvelle_Codes_PrefixHeader_pch
#define Luvelle_Codes_PrefixHeader_pch

// Include any system framework and library headers here that should be included in all compilation units.
// You will also need to set the Prefix Header build setting of one or more of your targets to reference this file.

#import "Constants.h"

#endif