如何在xcode中集成一个项目文件到另一个项目文件

Hello friends I developed an app in ios in that contains a database (coredata) the user can login with a username and a password and then he can store the personal details, pictures, files, documents.... Now, I want to link this Xcode project to another code project of mine so can anyone help how to add one Xcode project file to another. I tried by adding new files in Xcode but it was not showing project file which I want to add hope I'll get the best answer Hello friends I developed an app in ios in that