wallymathieu · September 20, 2022 19:32 · Sep 20, 2022 · Dec 5, 2020 · Nov 27, 2020
diff --git a/onion_1.ts b/onion_1.ts
@@ -0,0 +1,43 @@
+// 1_domain.ts
+// 1. pure, don't think about IO at all
+
+export function add(x: number, y: number) {
+  return x+y;
+}
+
+// 2_app.ts
+// 2. think about IO but not its implementation
+import * as Domain from './1_domain'
+
+export async function add( getX: () => Promise<number>, y: number) {
+  const x = await getX()
+  return Domain.add(x, y);
+}
+
+// 3_infra.ts
+// 3. IO implementation
+import fetch from 'node-fetch';
+
+export async function getX(apiUrl:string): Promise<number> {
+  const response = await fetch(apiUrl, { method: 'GET'});
+  const data = await response.json();
+  if (response.ok) {
+    return (data as number);
+  } else {
+    return Promise.reject(`Got an error response ${JSON.stringify(data)}`);
+  }
+}
+
+export function getConfigurationUrl() : string {
+  throw new Error('Function not implemented.');
+}
+
+// 4_index.ts
+import * as App from './2_app'
+import * as Infra from './3_infra'
+
+// 4. inject dependencies
+export function add (y:number){
+  const apiUrl = Infra.getConfigurationUrl();
+  return App.add ( ()=> Infra.getX(apiUrl), y);
+}
diff --git a/onion-1.fs b/onion-1.fs
@@ -4,7 +4,7 @@ module Domain =
 
 // 2. think about IO but not its implementation
 module App =
-    let add (getX: unit -> int32 Async) y =
+    let add (getX: unit -> Async<int32>) y =
         async {
             let! x = getX ()
             return Domain.add x y
@@ -18,6 +18,7 @@ module Infra =
 module Startup =
     let add = App.add Infra.getX
 
+// demo
 Startup.add 3
 |> Async.RunSynchronously
 |> printfn "%A" // 10
diff --git a/onion-2.fs b/onion-2.fs
@@ -4,7 +4,7 @@ module Domain =
 
 // 2. think about IO but not its implementation
 module App =
-    let add (getX: unit -> int32 Async) y =
+    let add (getX: unit -> Async<int32>) y =
         async {
             let! x = getX ()
             return Domain.add x y
@@ -24,6 +24,7 @@ module Startup =
             return! App.add (fun () -> Infra.getX conn) y
         }
 
+// demo
 Startup.add 3
 |> Async.RunSynchronously
 |> printfn "%A" // 10
diff --git a/onion-1.fs b/onion-1.fs
@@ -0,0 +1,23 @@
+// 1. pure, don't think about IO at all
+module Domain =
+    let add x y = x + y
+
+// 2. think about IO but not its implementation
+module App =
+    let add (getX: unit -> int32 Async) y =
+        async {
+            let! x = getX ()
+            return Domain.add x y
+        }
+
+// 3. IO implementation
+module Infra =
+    let getX () = async { return 7 }
+
+// 4. inject dependencies
+module Startup =
+    let add = App.add Infra.getX
+
+Startup.add 3
+|> Async.RunSynchronously
+|> printfn "%A" // 10
diff --git a/onion-2.fs b/onion-2.fs
@@ -0,0 +1,29 @@
+// 1. pure, don't think about IO at all
+module Domain =
+    let add x y = x + y
+
+// 2. think about IO but not its implementation
+module App =
+    let add (getX: unit -> int32 Async) y =
+        async {
+            let! x = getX ()
+            return Domain.add x y
+        }
+
+// 3. IO implementation
+module Infra =
+    open System.Data.SqlClient
+    let newConnection () = new SqlConnection ()
+    let getX conn = async { return 7 }
+
+// 4. inject dependencies
+module Startup =
+    let add y =
+        async {
+            use conn = Infra.newConnection ()
+            return! App.add (fun () -> Infra.getX conn) y
+        }
+
+Startup.add 3
+|> Async.RunSynchronously
+|> printfn "%A" // 10