selectors in tutorial

docs/tutorial-selectors.test.js

@@ -0,0 +1,27 @@
+import { test, expect } from 'vitest';
+
+import { Updux } from '../src/index.js';
+
+test( 'selectors', () => {
+    const dux = new Updux({
+        initial: { a: 1, b: 2 },
+        selectors: {
+            getA: ({a}) => a,
+            getBPlus: ({b}) => addition => b + addition,
+        },
+        subduxes: {
+            subbie: new Updux({
+                initial: { d: 3 },
+                selectors: {
+                    getD: ({d}) => d
+                    }
+            })
+        }
+    })
+
+    const store = dux.createStore();
+
+    expect( store.getState.getA() ).toEqual(1);
+    expect( store.getState.getBPlus(7) ).toEqual(9);
+    expect( store.getState.getD() ).toEqual(3);
+} );

docs/tutorial.md

@@ -126,8 +126,49 @@ store.dispatch.addTodo('Do the thing');
 ### Catch-all effect
 
 It is possible to have an effect match all actions via the special `*` token.
+
 ```
 todosUpdux.addEffect('*', () => next => action => {
     console.log( 'seeing action fly by:', action );
     next(action);
 });
+```
+
+## Adding selectors
+
+Selectors can be defined to get data derived from the state.
+From now you should know the drill: selectors can be defined at construction
+time or via `setSelector`.
+
+```
+const getTodoById = ({todos}) => targetId => todos.find(({id}) => id === targetId);
+
+const todosUpdux = new Updux({
+    selectors: {
+       getTodoById
+    }
+})
+```
+
+or
+
+```
+todosDux.setSelector('getTodoById', getTodoById);
+```
+
+### Accessing selectors
+
+The `getState` method of a dux store is augmented 
+with its selectors, with the first call for the state already
+called in for you. 
+
+```js
+const store = todosDux.createStore();
+
+console.log(
+    todosUpdux.getState.getTodoById(1)
+);
+```
+
+
+

src/Updux.js

@@ -148,20 +148,17 @@ export class Updux {
 
         store.actions = this.actions;
 
-        //        store.selectors = this.selectors;
+        store.selectors = this.selectors;
 
-        // store.getState = R.merge(
-        //     store.getState,
-        //     R.mapValues(this.selectors, (selector) => {
-        //         return (...args) => {
-        //             let result = selector(store.getState());
+        Object.entries(this.selectors).forEach(([selector, fn]) => {
+            store.getState[selector] = (...args) => {
+                let result = fn(store.getState());
 
-        //             if (typeof result === 'function') return result(...args);
+                if (typeof result === 'function') return result(...args);
 
-        //             return result;
-        //         };
-        //     })
-        // );
+                return result;
+            };
+        });
 
         for (const action in this.actions) {
             store.dispatch[action] = (...args) => {

src/createStore.test.js

@@ -11,6 +11,7 @@ test('basic createStore', async () => {
 
     const store = foo.createStore();
 
+    expect(store.getState).toBeTypeOf('function');
     expect(store.getState()).toEqual({ a: 1 });
 
     expect(store.actions.a1).toBeTypeOf('function');