iOS Unit Testing by Example

Replace String Literals to Use a View Model

The simplest place to begin a view model is to look for string literals. Search through ChangePasswordViewController, looking for double quotes. You will find:

• Various empty strings
• Alert messages
• The “OK” alert action label

The empty strings can remain. But let’s pull the other string literals into a view model. These strings don’t change, so we can start with a view model that doesn’t change state at first. Let’s begin by defining an empty view model. Add this file to the project:

MVVM/Refactoring/ChangePasswordViewModel.swift

struct ChangePasswordViewModel {
}

Then add it as a property in ChangePasswordViewController. In our case, we’re using a storyboard supporting iOS versions before ...