example and optimized none handling

Author: frawa

core/src/TeaCup/UpdatePiped.test.ts

@@ -23,22 +23,35 @@
  *
  */
 
-import { genericUpdatePiped } from "./UpdatePiped";
+import { Cmd } from './Cmd';
+import { genericUpdatePiped, updatePiped } from './UpdatePiped';
 
 describe('UpdatePiped', () => {
   type MyModel = number;
-  type MyCmd = string[];
+  type MyCmd = readonly string[];
 
   test('generic', () => {
-    const model0 : MyModel = 6;
+    const model0: MyModel = 6;
     const [model, cmd] = genericUpdatePiped(
-      (cmds: readonly MyCmd[]) => new Array().concat(...cmds),
+      (cmd1: MyCmd, cmd2: MyCmd) => new Array().concat(...cmd1, ...cmd2),
+      [],
       model0,
       (model) => [model + 1, ['add 1']],
       (model) => [model * 6, ['multiply by 6']],
     );
     expect(model).toBe(42);
     expect(cmd).toEqual(['add 1', 'multiply by 6']);
   });
-});
 
+  test('example with none handling', () => {
+    type MyMsg = string;
+    const model0: MyModel = 6;
+    const [model, cmd] = updatePiped(
+      model0,
+      (model) => [model + 1, Cmd.none()],
+      (model) => [model * 6, Cmd.none()],
+    );
+    expect(model).toBe(42);
+    expect(cmd).toEqual(Cmd.none());
+  });
+});

core/src/TeaCup/UpdatePiped.ts

@@ -35,7 +35,17 @@ export function updatePiped<Model, Msg>(
   model: Model,
   ...updates: readonly UpdateFunction<Model, Msg>[]
 ): [Model, Cmd<Msg>] {
-  return genericUpdatePiped(Cmd.batch, model, ...updates);
+  const none: Cmd<Msg> = Cmd.none();
+  const combine = (cmd1: Cmd<Msg>, cmd2: Cmd<Msg>) => {
+    const none1 = isNone(cmd1);
+    const none2 = isNone(cmd2);
+    return none1 && none2 ? cmd1 : none1 ? cmd2 : none2 ? cmd1 : Cmd.batch([cmd1, cmd2]);
+  };
+  return genericUpdatePiped(combine, none, model, ...updates);
+}
+
+function isNone<Msg>(cmd: Cmd<Msg>): boolean {
+  return cmd.constructor.name === 'CmdNone';
 }
 
 export type GenericUpdateFunction<Model, Cmd> = (model: Model) => [Model, Cmd];
@@ -45,17 +55,17 @@ export type GenericUpdateFunction<Model, Cmd> = (model: Model) => [Model, Cmd];
  * See updatePiped().
  */
 export function genericUpdatePiped<Model, Cmd>(
-  batch: (cmds: readonly Cmd[]) => Cmd,
+  combine: (cmd1: Cmd, cmd2: Cmd) => Cmd,
+  none: Cmd,
   model: Model,
   ...updates: readonly GenericUpdateFunction<Model, Cmd>[]
 ): [Model, Cmd] {
-  const cmd0: Cmd = batch([]);
   return updates.reduce<[Model, Cmd]>(
     (acc: [Model, Cmd], update: GenericUpdateFunction<Model, Cmd>) => {
       const [model0, cmd0] = acc;
       const [model1, cmd1] = update(model0);
-      return [model1, batch([cmd0, cmd1])];
+      return [model1, combine(cmd0, cmd1)];
     },
-    [model, cmd0],
+    [model, none],
   );
 }