How to add a module for modularisation using Swift Package Manager
The following article is part 2 of a 4-part series on modularisation in iOS with Swift Package Manager and some approaches we may take. If you missed out on part 1, feel free to check it out. As a reference for examples, we will be using this GitHub Repository.
We shall take the ModularisationStarter project and vertically modularise it as per the approach we discussed in part 1 of the series. The current structure of the starter project looks as follows:
Adding a package
We shall be taking Feature1 and moving it out into its module called Feature1Module. The module will be created using Swift Package Manager. To add a package, within Xcode select File > New > Package
Add an appropriate name to your package in our example we’ll call it Feature1Module and make sure to add it to a Packages folder or create one if it doesn’t exist. Once you’ve created your Packages folder make sure to modify the Add to: and select your current project. As a group select the Packages group you’ve recently created.
Once created, add your supported platforms with targets to the package.swift file of your module. Here we’ll add iOS supporting iOS15 as an example
Your project structure should now look like this with the newly added package.
We are then free to move the code from our Main App to the module as per the diagram in part 1.
In our main app, we need to then make sure to import Feature1Module wherever we may need it, in our case this would be in the AppDependencyContainer.
To show clearer separation within our package, we can create further modules within the Feature1Module. To do this restructure your package as follows
Next, we’ll modify our package.swift file to represent the different targets and the relationships between them.
As per our package.swift above we have exposed two targets(FeatureModule1UI and FeatureImplementations) which can then be used externally outside our package, as in the case of our main app.
Add modules as dependencies
In our example for horizontal modularisation, where we defined each module as a separate package we may need to add links between packages. For example, referring to the Horizontal modularisation example diagram in part 1 we will need a link for our Presentation Module to our Feature Module to use it. To do this add the relevant dependencies to the package.swift file as below
Once this is done we are free to import our Feature module wherever we may need it.
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Follow up article
In the next part of the series, we’ll learn how to integrate the package into our workflow.
