Add SQLite setup playground page

Playgrounds/ApolloMacPlayground.playground/Pages/SQLiteCache.xcplaygroundpage/Contents.swift

@@ -0,0 +1,66 @@
+//: [Subscriptons](@previous)
+
+import Apollo
+import Foundation
+import PlaygroundSupport
+
+//: # Setting up a client with a SQLite cache
+
+//: First, you'll need to set up a network transport, since you will also need that to set up the client:
+let serverURL = URL(string: "http://localhost:8080/graphql")!
+let networkTransport = HTTPNetworkTransport(url: serverURL)
+
+//: You'll need to make sure you import the ApolloSQLite library IF you are not using CocoaPods (CocoaPods will automatically flatten everything down to a single Apollo import):
+import ApolloSQLite
+
+//: Next, you'll have to figure out where to store your SQLite file. A reasonable place is the user's Documents directory in your sandbox.
+let documentsPath = NSSearchPathForDirectoriesInDomains(.documentDirectory, .userDomainMask, true).first!
+let documentsURL = URL(fileURLWithPath: documentsPath)
+let sqliteFileURL = documentsURL.appendingPathComponent("test_apollo_db.sqlite")
+
+print("File path: \(sqliteFileURL.path)")
+
+//: Use that file URL to instantiate the SQLite cache:
+let sqliteCache = try SQLiteNormalizedCache(fileURL: sqliteFileURL)
+
+//: And then instantiate an instance of `ApolloStore` with the cache you've just created:
+let store = ApolloStore(cache: sqliteCache)
+
+//: Finally, pass that into your `ApolloClient` initializer, and you're now set up to use the SQLite cache for persistent storage:
+let apolloClient = ApolloClient(networkTransport: networkTransport, store: store)
+
+
+//: Now, let's test
+import StarWarsAPI
+let query = HeroDetailsQuery(episode: .newhope)
+apolloClient.fetch(query: query) { result in
+    // This is the outer Result, which has either a `GraphQLResult` or an `Error`
+    switch result {
+    case .success(let graphQLResult):
+        if let errors = graphQLResult.errors {
+            // Errors here were returned by the GraphQL system.
+            // Note that the presence of errors does NOT necessarily indicate a request failed: GraphQL requests can return partial results in the event of an error.
+            print("GraphQL errors: \(errors)")
+        }
+
+        if let hero = graphQLResult.data?.hero {
+            // Here, we've used a type-safe accessor to the nested type to access the specific type with the specific fields requested by this query.
+            print("Hero name: \(hero.name)")
+        }
+    case .failure(let error):
+        // If this happens, something's gone wrong at the network level before the GraphQL server could respond.
+        print("Network error: \(error)")
+    }
+}
+
+//: Give the database write a chance to finish before the playground finishes executing
+DispatchQueue.main.asyncAfter(deadline: .now() + 1) {
+    print("FINISHED")
+    PlaygroundPage.current.finishExecution()
+}
+
+PlaygroundPage.current.needsIndefiniteExecution = true
+
+//: Once "FINISHED" prints, you can open the database file at the path printed out with "File path" and examine it to see the persisted data.
+
+//: [Next](@next)

Playgrounds/ApolloMacPlayground.playground/Pages/Subscriptions.xcplaygroundpage/Contents.swift

@@ -126,3 +126,5 @@ for _ in 0..<loops {
 }
 
 PlaygroundPage.current.needsIndefiniteExecution = true
+
+//: [SQLiteCache](@next)

Playgrounds/ApolloMacPlayground.playground/contents.xcplayground

@@ -1,5 +1,5 @@
 <?xml version="1.0" encoding="UTF-8" standalone="yes"?>
-<playground version='6.0' target-platform='macos' display-mode='rendered' buildActiveScheme='true'>
+<playground version='6.0' target-platform='macos' display-mode='raw' buildActiveScheme='true'>
     <pages>
         <page name='Introduction'/>
         <page name='Queries'/>