state preservation when replacing a reducer: continue incrementing th…

…e id
reduxjs · Jul 1, 2015 · 4c3101c · 4c3101c
1 parent 34d90b9
commit 4c3101c
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Showing 2 changed files with 12 additions and 6 deletions.
diff --git a/test/Store.spec.js b/test/Store.spec.js
@@ -95,7 +95,7 @@ describe('Store', () => {
 
     store.dispatch(addTodo('Perhaps'));
     expect(store.getState()).toEqual([{
-      id: 2,
+      id: 3,
       text: 'Perhaps'
     }, {
       id: 1,
@@ -108,7 +108,7 @@ describe('Store', () => {
     nextStore = new Store(todos);
     store.replaceReducer(nextStore.getReducer());
     expect(store.getState()).toEqual([{
-      id: 2,
+      id: 3,
       text: 'Perhaps'
     }, {
       id: 1,
@@ -120,7 +120,7 @@ describe('Store', () => {
 
     store.dispatch(addTodo('Surely'));
     expect(store.getState()).toEqual([{
-      id: 2,
+      id: 3,
       text: 'Perhaps'
     }, {
       id: 1,
@@ -129,7 +129,7 @@ describe('Store', () => {
       id: 2,
       text: 'World'
     }, {
-      id: 3,
+      id: 4,
       text: 'Surely'
     }]);
   });

diff --git a/test/helpers/reducers.js b/test/helpers/reducers.js
@@ -1,10 +1,16 @@
 import { ADD_TODO } from './actionTypes';
 
+
+var id = (state = []) =>
+  state.reduce((id, item) => (
+    item.id > id ? item.id : id
+  ), 0) + 1;
+
 export function todos(state = [], action) {
   switch (action.type) {
   case ADD_TODO:
     return [...state, {
-      id: state.length ? state[state.length - 1].id + 1 : 1,
+      id: id(state),
       text: action.text
     }];
   default:
@@ -16,7 +22,7 @@ export function todosReverse(state = [], action) {
   switch (action.type) {
   case ADD_TODO:
     return [{
-      id: state.length ? state[0].id + 1 : 1,
+      id: id(state),
       text: action.text
     }, ...state];
   default: