搭建node服務（四)：Decorator裝飾器

{"type":"doc","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"Decorator（裝飾器）是ECMAScript中一種與class相關的語法，用於給對象在運行期間動態的增加功能。Node.js 還不支持Decorator，可以使用Babel進行轉換，也可以在TypeScript中使用Decorator。本示例則是基於TypeScript來介紹如何在node服務中使用Decorator。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"heading","attrs":{"align":null,"level":2},"content":[{"type":"text","text":"一、 TypeScript相關"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"由於使用了 TypeScript ，需要安裝TypeScript相關的依賴，並在根目錄添加 tsconfig.json 配置文件，這裏不再詳細說明。要想在 TypeScript 中使用Decorator 裝飾器，必須將 tsconfig.json 中 experimentalDecorators設置爲true，如下所示："}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"heading","attrs":{"align":null,"level":3},"content":[{"type":"text","text":"tsconfig.json"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"codeblock","attrs":{"lang":""},"content":[{"type":"text","text":"{\n \"compilerOptions\": {\n …\n \/\/ 是否啓用實驗性的ES裝飾器\n \"experimentalDecorators\": true\n }\n}"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"heading","attrs":{"align":null,"level":2},"content":[{"type":"text","text":"二、 裝飾器介紹"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"heading","attrs":{"align":null,"level":3},"content":[{"type":"text","text":"1. 簡單示例"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"Decorator實際是一種語法糖，下面是一個簡單的用TypeScript編寫的裝飾器示例："}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"codeblock","attrs":{"lang":""},"content":[{"type":"text","text":"const Controller: ClassDecorator = (target: any) => {\n target.isController = true;\n};\n@Controller\nclass MyClass {\n}\nconsole.log(MyClass.isController); \/\/ 輸出結果：true"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"Controller是一個類裝飾器，在MyClass類聲明前以 @Controller 的形式使用裝飾器，添加裝飾器後MyClass. isController 的值爲true。 編譯後的代碼如下："}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"codeblock","attrs":{"lang":""},"content":[{"type":"text","text":"var __decorate = (this && this.__decorate) || function (decorators, target, key, desc) {\n var c = arguments.length, r = c < 3 ? target : desc === null ? desc = Object.getOwnPropertyDescriptor(target, key) : desc, d;\n if (typeof Reflect === \"object\" && typeof Reflect.decorate === \"function\") r = Reflect.decorate(decorators, target, key, desc);\n else for (var i = decorators.length - 1; i >= 0; i--) if (d = decorators[i]) r = (c < 3 ? d(r) : c > 3 ? d(target, key, r) : d(target, key)) || r;\n return c > 3 && r && Object.defineProperty(target, key, r), r;\n};\nconst Controller = (target) => {\n target.isController = true;\n};\nlet MyClass = class MyClass {\n};\nMyClass = __decorate([\n Controller\n], MyClass);"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"heading","attrs":{"align":null,"level":3},"content":[{"type":"text","text":"2. 工廠方法"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}}]}