This is one of the simplest but could also be the toughest to crack.
Imagine this, you wrote most of the Database class for your new application . At the same time you have created your database schema, and save a copy of the file (.sqlite) in where your project folder is.
You tried running the codes but it seems that there’s a error with the file not found.
To resolve this simply add the Application.sqlite file to your xcode project.
Then make sure that under Targets-> Build Phases -> Copy Bundle Resources, you have your Application.sqlite in there.
To really confirm again, when you have ran your simulator once, you can browse to the following path,
/Users/<yourname>/Library/Application Support/iPhone Simulator/5.0/Applications/<GUID>/<ApplicationName>.app
Right Click on the file and show content.