Prefix header file is precompiled header file. Its automatically included while you create a new project. Normally developers use this file to declare common headers used in view controllers. Also used to import common frameworks. Headers & frameworks declared in prefix header will be accessible to all view controllers without creating any reference to it as it precompiled.

So from this point of view its very useful file & manages reusability & allows a user not to import frameworks again & again for each view controllers. Now if in your project prefix file is not present you can create it manually by following simple steps.

Here are the step to create and setup a Prefix Header File for iOS,

Right click on resources folder & click the new file

Select PCH file from others
Name it with exactly your project name & save it

Now go to targets -> build settings & find prefix header row. Now set a path for prefix header in the row. A path would be like, APPNAME/PREFIX FILENAME

Read more: Healthy iOS Development Tips & Tricks

That’s it!!! Now you can declare headers, common frameworks & third party classes which are commonly used.