65 lines
1.5 KiB
Dart
65 lines
1.5 KiB
Dart
/**
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策略模式（Strategy Pattern）
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意图：定义一系列的算法,把它们一个个封装起来, 并且使它们可相互替换。
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主要解决：在有多种算法相似的情况下，使用 if...else 所带来的复杂和难以维护。
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何时使用：一个系统有许多许多类，而区分它们的只是他们直接的行为。
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如何解决：将这些算法封装成一个一个的类，任意地替换。
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*/
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main(List<String> args) {
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Context context = new Context(new OperationAdd());
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print("10 + 5 = ${context.executeStrategy(10, 5)}");
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context = new Context(new OperationSubstract());
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print("10 - 5 = ${context.executeStrategy(10, 5)}");
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context = new Context(new OperationMultiply());
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print("10 * 5 = ${context.executeStrategy(10, 5)}");
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}
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//////////////////////////////////////////////////////////////////
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///
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/// 创建一个接口
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///
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abstract class Strategy {
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int doOperation(int num1, int num2);
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}
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///
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/// 创建实现接口的实体类
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///
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class OperationAdd implements Strategy {
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@override
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int doOperation(int num1, int num2) {
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return num1 + num2;
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}
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}
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class OperationSubstract implements Strategy {
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@override
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int doOperation(int num1, int num2) {
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return num1 - num2;
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}
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}
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class OperationMultiply implements Strategy {
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@override
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int doOperation(int num1, int num2) {
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return num1 * num2;
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}
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}
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///
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/// 创建 Context 类
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///
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class Context {
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Strategy _strategy;
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Context(this._strategy);
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int executeStrategy(int num1, int num2) {
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return _strategy.doOperation(num1, num2);
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}
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}
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