4.14, redux middleware

trance128 · Sep 13, 2020 · 1ddca82 · 1ddca82
1 parent 5ea6761
commit 1ddca82
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Showing 4 changed files with 64 additions and 17 deletions.
diff --git a/redux_tut/lib/main.dart b/redux_tut/lib/main.dart
@@ -1,14 +1,15 @@
 import 'package:flutter/material.dart';
 import 'package:flutter_redux/flutter_redux.dart';
 import 'package:redux/redux.dart';
-import 'package:redux_tut/redux/reducers.dart';
-import 'package:redux_tut/redux/store.dart';
 
+import 'redux/middleware.dart';
+import 'redux/reducers.dart';
+import 'redux/store.dart';
 import 'screens/home_screen.dart';
 
 void main() {
   Store<AppState> _store =
-      Store<AppState>(reducers, initialState: AppState.initial());
+      Store<AppState>(reducers, initialState: AppState.initial(), middleware: [appStateMiddleware]);
 
   runApp(MyApp(store: _store));
 }

diff --git a/redux_tut/lib/redux/actions.dart b/redux_tut/lib/redux/actions.dart
@@ -9,3 +9,17 @@ class UpdateKm extends Action {
     this.payload,
   );
 }
+
+class UpdateKmCleaned extends Action {
+  String payload;
+
+  UpdateKmCleaned(
+    this.payload,
+  );
+}
+
+class UpdateMiles extends Action {
+  String payload;
+
+  UpdateMiles(this.payload);
+}
diff --git a/redux_tut/lib/redux/middleware.dart b/redux_tut/lib/redux/middleware.dart
@@ -0,0 +1,37 @@
+import 'package:redux/redux.dart';
+import 'package:redux_tut/redux/actions.dart';
+import 'store.dart';
+
+bool isNumeric(String c) {
+  /// isNumeric takes a string of length 1
+  /// returns true if string is numeric, returns false otherwise
+  
+  return c.compareTo('0') >= 0 && c.compareTo('9') <= 0;
+}
+
+void appStateMiddleware(Store<AppState> store, dynamic action, NextDispatcher next) {
+  print("In the middleware");
+
+  if (action is UpdateKm) {
+    String cleanedString = '';
+    for (String c in action.payload.split('')) {
+      if (isNumeric(c)) {
+        print("Adding $c to cleanedString");
+        cleanedString += c;
+        print("cleanedString is $cleanedString");
+      } else {
+        print("$c is not recognized as numeric");
+      }
+    }
+
+    store.dispatch(UpdateKmCleaned(cleanedString));
+  } else if (action is Convert) {
+    print("Action is convert");
+    double kmAsDouble = double.parse(store.state.km);
+    double milesAsDouble = kmAsDouble * 0.621371;
+
+    store.dispatch(UpdateMiles(milesAsDouble.toString()));
+  }
+
+  next(action);
+}
diff --git a/redux_tut/lib/redux/reducers.dart b/redux_tut/lib/redux/reducers.dart
@@ -2,21 +2,16 @@ import 'actions.dart';
 import 'store.dart';
 
 AppState reducers(AppState prevState, dynamic action) {
-  AppState newState;
+  print("-------------");
+  print("In the reducer");
 
-  if (action is UpdateKm) {
-    newState = AppState.copyWith(prev: prevState, km: action.payload);
-  } else if (action is Convert) {
+  if (action is UpdateKmCleaned) {
     print(action);
-    //! THE FOLLOW CODE BELONGS IN MIDDLEWARE
-    //! NOT IN REDUCERS!!
-    double kmAsDouble = double.parse(prevState.km);
-    double milesAsDouble = kmAsDouble * 0.621371;
-
-    print(milesAsDouble);
-
-    newState = AppState.copyWith(prev: prevState, miles: milesAsDouble.toString());
+    return AppState.copyWith(prev: prevState, km: action.payload);
+  } else if (action is UpdateMiles) {
+    print(action);
+    return AppState.copyWith(prev: prevState, miles: action.payload);
+  } else {
+    return AppState(miles: prevState.miles, km: prevState.km);
   }
-
-  return newState;
 }