Added reminder to use the .fetch() in the reduce() when using NumberF…

[siliconsorcery]

Small update for the documentation. This should help beginners avoid the confusion I found myself in.

[stephencelis]

@siliconsorcery Thanks for taking the time to PR! I think that code is already taken care of here, though:

swift-composable-architecture/README.md

Lines 392 to 399 in a658e25

	Then we can use it in the `reduce` implementation:
	```swift
	case .numberFactButtonTapped:
	return .task { [count = state.count] in
	await .numberFactResponse(TaskResult { try await self.numberFact(count) })
	}
	```

Luckily, switching from holding onto a dependency explicitly as a property vs. implicitly through a property wrapper means the call site in reduce doesn't need to change!

[siliconsorcery]

@stephencelis Thanks for your response.

Unless I missed a step, we are using a variable to hold our function to fetch a number fact. The default definition is set in:

extension NumberFactClient: DependencyKey {
  static let liveValue = Self(
    fetch: ..
 )
}

It can be overridden for testing

let store = TestStore(
  initialState: Feature.State(),
  reducer: Feature()
) {
  $0.numberFact.fetch = { "\($0) is a good number Brent" }
}

Note we are referencing the fetch function we are replacing.

Now for usage we need to call the fetch function.

        case .numberFactButtonTapped:
            return .task { [count = state.count] in
                await .numberFactResponse(
                    TaskResult {
                        try await self.numberFact.fetch(count)
                    }
                )
            }

If I omit the fetch function

  try await self.numberFact(count)

Xcode throws an error: Cannot call value of non-function type 'NumberFactClient'

This had me very confused until I studied the code.

Again, unless I missed something, I think the correct function access for all uses (production, development and testing) in this case is to call the fetch function.

  try await self.numberFact.fetch(count)

Thanks four your great work.

[stephencelis]

@siliconsorcery Ah you're right. I overlooked the .fetch. Will chat with @mbrandonw about this just to see if there's a way of minimizing README steps, but good catch, thanks!

[stephencelis]

@siliconsorcery Rather than add another step and more prose, what do you think of folding the required change into this code block:

swift-composable-architecture/README.md

Lines 497 to 504 in d73a349

	```swift
	struct Feature: ReducerProtocol {
	struct State { … }
	enum Action { … }
	@Dependency(\.numberFact) var numberFact
	…
	}
	```

Basically change it to this diff instead?

 struct Feature: ReducerProtocol {
   …
-  let numberFact: (Int) async throws -> String
+  @Dependency(\.numberFact) var numberFact
   …
-  try await self.numberFact(count)
+  try await self.numberFact.fetch(count)
   …
 }

[mbrandonw]

Hi @siliconsorcery, I have made the changes that @stephencelis mentioned and think it reads better now. Will merge this and hopefully it helps people in the future.

Thanks for bringing this up!