feature: #2151 Feature/mvi pattern (#2177)

* #2151 add module and pom.xml * #2151 add Calculator Actions * #2151 add remaining mvi pattern classes (actions already implemented) * #2151 add Main and unit tests * add README.md and class diagrams * #2151 add module and pom.xml * #2151 add Calculator Actions * #2151 add remaining mvi pattern classes (actions already implemented) * #2151 add Main and unit tests * add README.md and class diagrams * fixes for lint errors * #2151 add module and pom.xml * #2151 add Calculator Actions * #2151 add remaining mvi pattern classes (actions already implemented) * #2151 add Main and unit tests * add README.md and class diagrams * fixes for lint errors * use Lombok @Data decorator and decouple View from ViewModel * add comments and documentation * fix checkstyle, the smart switch syntax was breaking checkstyle, so I had to change it back
2026-05-16 04:58:46 +00:00 · 2023-01-21 10:45:07 +01:00
parent 6b0a90ee61
commit fb86ca1156
19 changed files with 943 additions and 0 deletions
@@ -0,0 +1,87 @@
+/*
+ * This project is licensed under the MIT license.
+ * Module model-view-viewmodel is using ZK framework licensed under LGPL
+ * (see lgpl-3.0.txt).
+ *
+ * The MIT License
+ * Copyright © 2014-2022 Ilkka Seppälä
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+package com.iluwatar.model.view.intent;
+
+/**
+ * Model-View-Intent is a pattern for implementing user interfaces.
+ * Its main advantage over MVVM  which it closely mirrors is a
+ * minimal public api with which user events can be exposed to the ViewModel.
+ * In case of the MVI every event is exposed by using a single method
+ * with 1 argument which implements UserEvent interface.
+ * Specific parameters can be expressed as its parameters. In this case,
+ * we'll be using MVI to implement a simple calculator
+ * with +, -, /, * operations and the ability to set the variable.
+ * It's important to note, that every user action happens through the
+ * view, we never interact with the ViewModel directly.
+ */
+public final class App {
+
+
+  /**
+   * To avoid magic value lint error.
+   */
+  private static final double RANDOM_VARIABLE = 10.0;
+
+  /**
+   * Program entry point.
+   *
+   * @param args command line args
+   */
+  public static void main(final String[] args) {
+    // create model, view and controller
+
+    // initialize calculator view, output and variable = 0
+    var view = new CalculatorView(new CalculatorViewModel());
+    var variable1 = RANDOM_VARIABLE;
+
+    // calculator variable = RANDOM_VARIABLE -> 10.0
+    view.setVariable(variable1);
+
+    // add calculator variable to output -> calculator output = 10.0
+    view.add();
+    view.displayTotal();  // display output
+
+    variable1 = 2.0;
+    view.setVariable(variable1);  // calculator variable = 2.0
+
+    // subtract calculator variable from output -> calculator output = 8
+    view.subtract();
+
+    // divide calculator output by variable -> calculator output = 4.0
+    view.divide();
+
+    // multiply calculator output by variable -> calculator output = 8.0
+    view.multiply();
+    view.displayTotal();
+  }
+
+  /**
+   * Avoid default constructor lint error.
+   */
+  private App() {
+  }
+}
@@ -0,0 +1,23 @@
+package com.iluwatar.model.view.intent;
+
+import lombok.Data;
+import lombok.Getter;
+
+/**
+ * Current state of calculator.
+ */
+@Data
+public class CalculatorModel {
+
+  /**
+   * Current calculator variable used for operations.
+   **/
+  @Getter
+  private final Double variable;
+
+  /**
+   * Current calculator output -> is affected by operations.
+   **/
+  @Getter
+  private final Double output;
+}
@@ -0,0 +1,74 @@
+package com.iluwatar.model.view.intent;
+
+import com.iluwatar.model.view.intent.actions.AdditionCalculatorAction;
+import com.iluwatar.model.view.intent.actions.DivisionCalculatorAction;
+import com.iluwatar.model.view.intent.actions.MultiplicationCalculatorAction;
+import com.iluwatar.model.view.intent.actions.SetVariableCalculatorAction;
+import com.iluwatar.model.view.intent.actions.SubtractionCalculatorAction;
+import lombok.Data;
+import lombok.Getter;
+import lombok.extern.slf4j.Slf4j;
+
+/**
+ * Exposes changes to the state of calculator
+ * to {@link CalculatorViewModel} through
+ * {@link com.iluwatar.model.view.intent.actions.CalculatorAction}
+ * and displays its updated {@link CalculatorModel}.
+ */
+@Slf4j
+@Data
+public class CalculatorView {
+
+  /**
+   * View model param handling the operations.
+   */
+  @Getter
+  private final CalculatorViewModel viewModel;
+
+  /**
+   * Display current view model output with logger.
+   */
+  void displayTotal() {
+    LOGGER.info(
+        "Total value = {}",
+        viewModel.getCalculatorModel().getOutput().toString()
+    );
+  }
+
+  /**
+   * Handle addition action.
+   */
+  void add() {
+    viewModel.handleAction(new AdditionCalculatorAction());
+  }
+
+  /**
+   * Handle subtraction action.
+   */
+  void subtract() {
+    viewModel.handleAction(new SubtractionCalculatorAction());
+  }
+
+  /**
+   * Handle multiplication action.
+   */
+  void multiply() {
+    viewModel.handleAction(new MultiplicationCalculatorAction());
+  }
+
+  /**
+   * Handle division action.
+   */
+  void divide() {
+    viewModel.handleAction(new DivisionCalculatorAction());
+  }
+
+  /**
+   * Handle setting new variable action.
+   *
+   * @param value -> new calculator variable.
+   */
+  void setVariable(final Double value) {
+    viewModel.handleAction(new SetVariableCalculatorAction(value));
+  }
+}
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+package com.iluwatar.model.view.intent;
+
+import com.iluwatar.model.view.intent.actions.AdditionCalculatorAction;
+import com.iluwatar.model.view.intent.actions.CalculatorAction;
+import com.iluwatar.model.view.intent.actions.DivisionCalculatorAction;
+import com.iluwatar.model.view.intent.actions.MultiplicationCalculatorAction;
+import com.iluwatar.model.view.intent.actions.SetVariableCalculatorAction;
+import com.iluwatar.model.view.intent.actions.SubtractionCalculatorAction;
+
+/**
+ * Handle transformations to {@link CalculatorModel}
+ * based on intercepted {@link CalculatorAction}.
+ */
+public final class CalculatorViewModel {
+
+  /**
+   * Current calculator model (can be changed).
+   */
+  private CalculatorModel model =
+      new CalculatorModel(0.0, 0.0);
+
+  /**
+   * Handle calculator action.
+   *
+   * @param action -> transforms calculator model.
+   */
+  void handleAction(final CalculatorAction action) {
+    switch (action.tag()) {
+      case AdditionCalculatorAction.TAG:
+        add();
+        break;
+
+      case SubtractionCalculatorAction.TAG:
+        subtract();
+        break;
+
+      case MultiplicationCalculatorAction.TAG:
+        multiply();
+        break;
+
+      case DivisionCalculatorAction.TAG:
+        divide();
+        break;
+
+      case SetVariableCalculatorAction.TAG:
+        SetVariableCalculatorAction setVariableAction =
+            (SetVariableCalculatorAction) action;
+        setVariable(setVariableAction.getVariable());
+        break;
+
+      default:
+        break;
+    }
+  }
+
+  /**
+   * Getter.
+   *
+   * @return current calculator model.
+   */
+  public CalculatorModel getCalculatorModel() {
+    return model;
+  }
+
+  /**
+   * Set new calculator model variable.
+   *
+   * @param variable -> value of new calculator model variable.
+   */
+  private void setVariable(final Double variable) {
+    model = new CalculatorModel(
+        variable,
+        model.getOutput()
+    );
+  }
+
+  /**
+   * Add variable to model output.
+   */
+  private void add() {
+    model = new CalculatorModel(
+        model.getVariable(),
+        model.getOutput() + model.getVariable()
+    );
+  }
+
+  /**
+   * Subtract variable from model output.
+   */
+  private void subtract() {
+    model = new CalculatorModel(
+        model.getVariable(),
+        model.getOutput() - model.getVariable()
+    );
+  }
+
+  /**
+   * Multiply model output by variable.
+   */
+  private void multiply() {
+    model = new CalculatorModel(
+        model.getVariable(),
+        model.getOutput() * model.getVariable()
+    );
+  }
+
+  /**
+   * Divide model output by variable.
+   */
+  private void divide() {
+    model = new CalculatorModel(
+        model.getVariable(),
+        model.getOutput() / model.getVariable()
+    );
+  }
+}
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+package com.iluwatar.model.view.intent.actions;
+
+/**
+ * Addition {@link CalculatorAction}.
+ * */
+public class AdditionCalculatorAction implements CalculatorAction {
+  /**
+   * Subclass tag.
+   * */
+  public static final String TAG = "ADDITION";
+
+  /**
+   * Makes checking subclass type trivial.
+   * */
+  @Override
+  public String tag() {
+    return TAG;
+  }
+}
@@ -0,0 +1,15 @@
+package com.iluwatar.model.view.intent.actions;
+
+/**
+ * Defines what outside interactions can be consumed by view model.
+ * */
+public interface CalculatorAction {
+
+  /**
+   * Makes identifying action trivial.
+   *
+   * @return subclass tag.
+   * */
+  String tag();
+}
+
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+package com.iluwatar.model.view.intent.actions;
+
+/**
+ *  Division {@link CalculatorAction}.
+ * */
+public class DivisionCalculatorAction implements CalculatorAction {
+  /**
+   * Subclass tag.
+   * */
+  public static final String TAG = "DIVISION";
+
+  /**
+   * Makes checking subclass type trivial.
+   * */
+  @Override
+  public String tag() {
+    return TAG;
+  }
+}
@@ -0,0 +1,19 @@
+package com.iluwatar.model.view.intent.actions;
+
+/**
+ *  Multiplication {@link CalculatorAction}.
+ * */
+public class MultiplicationCalculatorAction implements CalculatorAction {
+  /**
+   * Subclass tag.
+   * */
+  public static final String TAG = "MULTIPLICATION";
+
+  /**
+   * Makes checking subclass type trivial.
+   * */
+  @Override
+  public String tag() {
+    return TAG;
+  }
+}
@@ -0,0 +1,30 @@
+package com.iluwatar.model.view.intent.actions;
+
+import lombok.Data;
+import lombok.Getter;
+
+/**
+ * SetVariable {@link CalculatorAction}.
+ */
+@Data
+public final class SetVariableCalculatorAction implements CalculatorAction {
+
+  /**
+   * Subclass tag.
+   */
+  public static final String TAG = "SET_VARIABLE";
+
+  /**
+   * Used by {@link com.iluwatar.model.view.intent.CalculatorViewModel}.
+   */
+  @Getter
+  private final Double variable;
+
+  /**
+   * Makes checking subclass type trivial.
+   */
+  @Override
+  public String tag() {
+    return TAG;
+  }
+}
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+package com.iluwatar.model.view.intent.actions;
+
+/**
+ *  Subtraction {@link CalculatorAction}.
+ * */
+public class SubtractionCalculatorAction implements CalculatorAction {
+  /**
+   * Subclass tag.
+   * */
+  public static final String TAG = "SUBTRACTION";
+
+  /**
+   * Makes checking subclass type trivial.
+   * */
+  @Override
+  public String tag() {
+    return TAG;
+  }
+}
@@ -0,0 +1,6 @@
+/**
+ * Handle actions for {@link com.iluwatar.model.view.intent.CalculatorModel}
+ * defined by {@link com.iluwatar.model.view.intent.actions.CalculatorAction}.
+ */
+
+package com.iluwatar.model.view.intent.actions;
@@ -0,0 +1,6 @@
+/**
+ * Define Model, View and ViewModel.
+ * Use them in {@link com.iluwatar.model.view.intent.App}
+ */
+
+package com.iluwatar.model.view.intent;