Mastering MVVM With Swift

Episode 1

Welcome to Mastering MVVM With Swift


Welcome to Mastering MVVM With Swift. In this series, you learn the ins and outs of the Model-View-ViewModel pattern. The goal is to provide you with the ingredients you need to implement the Model-View-ViewModel pattern in your own projects.

Episode 2

Is the Model-View-Controller Pattern Dead


Model-View-Controller, or MVC for short, is a widely used design pattern for architecting software applications. Cocoa applications are centered around the Model-View-Controller pattern and many of Apple's frameworks make heavy use of the Model-View-Controller pattern.

Episode 4

Meet Cloudy


In the remainder of this series, we refactor an application that is built with the Model-View-Controller pattern and make it adopt the Model-View-ViewModel pattern instead. This will answer two important questions. (1) What are the shortcomings of the MVC pattern? (2) How can the MVVM pattern help resolve these shortcomings?

Episode 5

What Is Wrong With Cloudy


Now that you have an idea of the ins and outs of Cloudy, I'd like to take a few minutes to highlight some of Cloudy's issues. Keep in mind that Cloudy is a small project. The problems we're going to fix with the Model-View-ViewModel pattern are less apparent, which is why I'd like to highlight them before we fix them.

Episode 6 Plus

A Quick Recap


Before you create your first view model, I want to revisit the internals of the Model-View-ViewModel pattern. We need to keep the following in mind. The model is owned by the view model. The controller doesn't know about and cannot access the model. The controller owns the view model and the view model doesn't know about the controller it is owned by.

Episode 7

Time to Create a View Model


In this episode, we create a view model for the day view controller. Fire up Xcode and open the starter project of this episode. We start by creating a new group, View Models, in the Weather View Controllers group. I prefer to keep the view models close to the view controllers in which they are used.

Episode 8 Plus

Put the View Model to Work


If you are not sure how the various pieces of the Model-View-ViewModel pattern fit together, then this episode will be helpful. In this episode, we put the DayViewModel struct we created in the previous episode to use. This means that we need to refactor the DayViewController and the RootViewController classes.

Episode 9 Plus

Rinse and Repeat


In this episode, we shift focus to the WeekViewController class. To adopt the Model-View-ViewModel pattern in the WeekViewController class, we start by creating a type for the view model of the week view controller. Create a new file in the View Models group and name the file WeekViewModel.swift.

Episode 10 Plus

Using MVVM In the Settings View


The Model-View-ViewModel pattern isn't only useful for populating data-driven user interfaces. In this episode, I show you how to apply the MVVM pattern in the SettingsViewController class.

Episode 11 Plus

Adding Protocols to the Mix


In the previous episode, I mentioned that we are repeating ourselves in the tableView(_:cellForRowAt:) method of the SettingsViewController class. We can resolve this problem with protocol-oriented programming.

Episode 13 Plus

Supercharging MVVM With Protocols


Let's apply what we learned in the previous episodes to the week view controller. The week view controller currently configures the cells of its table view. That is something we want to change. The refactoring of the week view controller involves four steps. We create a view model for each table view cell. The WeekViewModel struct generates a view model for each table view cell. We define a protocol to which the view models for the table view cells conform. The WeatherDayTableViewCell class has the ability to configure itself using a view model.

Episode 14

Ready, Set, Test


Because we moved a fair bit of logic from the view controllers of the project to the view models, we gained an important advantage, improved testability. As I mentioned earlier in this series, unit testing view controllers is known to be difficult. View models, however, are easy to test and that is the focus of the next few episodes.

Episode 15

Testing Your First View Model


In this episode, we unit test the view models of the settings view controller. We start with the SettingsTimeViewModel struct. Create a new file in the Test Cases group and select the Unit Test Case Class template.

Episode 16

Using Stubs for Better Unit Tests


Unit testing the DayViewModel struct isn't very different from unit testing the view models of the SettingsViewController class. The only tricky aspect is creating a DayViewModel object in a unit test.

Episode 17 Plus

A Few More Unit Tests


Writing units tests for the view models of the WeekViewController class is just as easy as writing unit tests for the DayViewModel struct. We start with the unit tests for the WeekViewModel struct.

Episode 18

Taking MVVM to the Next Level


You should now have a good understanding of what the Model-View-ViewModel pattern is and how it can be used to cure some of the problems the Model-View-Controller pattern suffers from. We can do better, though. Data is currently flowing in one direction. The view controller asks its view model for data and populates the view it manages. This is fine and many projects can greatly benefit from this lightweight implementation of the Model-View-ViewModel pattern.

Episode 19 Plus

What Are the Options


How do we bind the various components of the Model-View-ViewModel pattern together? That is the question we focus on in the next few episodes. It is a problem most developers new to the MVVM pattern struggle with. It isn't difficult to use the Model-View-ViewModel pattern to push data from the controller layer to the view layer. We already covered that extensively in this series. What do we need to change to automatically update the user interface if the user interacts with the application or the environment changes?