AnimalsDataClient

When building products with dependencies on complex services like SwiftData, it can be very handy to be able to run things “end-to-end” outside our UI. We can think of this as an “integration test”; this is in addition to — not a replacement for — conventional unit tests.

Before we build our component tree and put these data models on-screen, let’s build a simple command-line executable against our LocalStore. Our AnimalsDataClient executable will build against our production LocalStore class and persist its data on our filesystem. This means we can run our AnimalsDataClient executable, mutate our data, and see that new data the next time we run.

To run against SwiftData from a command-line executable, we need a little work to configure our module.¹ The Workspace from the ImmutableData-Samples repo already includes this configuration to save us some time. All we have to do is select the AnimalsData package and open Sources/AnimalsDataClient/main.swift.

Here is all we need to begin operating on a LocalStore:

//  main.swift

import AnimalsData
import Foundation

func makeLocalStore() throws -> LocalStore<UUID> {
  if let url = Process().currentDirectoryURL?.appending(
    component: "default.store",
    directoryHint: .notDirectory
  ) {
    return try LocalStore<UUID>(url: url)
  }
  return try LocalStore<UUID>()
}

func main() async throws {
  let store = try makeLocalStore()
  
  let animals = try await store.fetchAnimalsQuery()
  print(animals)
  
  let categories = try await store.fetchCategoriesQuery()
  print(categories)
}

try await main()

Our main function builds a LocalStore instance. We can then read from our LocalStore and perform mutations.

Try it for yourself: think of this executable as a “playground”. Try adding mutations. Run your executable again and confirm the mutations were persisted.

1. https://forums.developer.apple.com/forums/thread/734540 ↩