搭建node服务（四)：Decorator装饰器

{"type":"doc","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"Decorator（装饰器）是ECMAScript中一种与class相关的语法，用于给对象在运行期间动态的增加功能。Node.js 还不支持Decorator，可以使用Babel进行转换，也可以在TypeScript中使用Decorator。本示例则是基于TypeScript来介绍如何在node服务中使用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相关"}]},{"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":"由于使用了 TypeScript ，需要安装TypeScript相关的依赖，并在根目录添加 tsconfig.json 配置文件，这里不再详细说明。要想在 TypeScript 中使用Decorator 装饰器，必须将 tsconfig.json 中 experimentalDecorators设置为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 \/\/ 是否启用实验性的ES装饰器\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、 装饰器介绍"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"heading","attrs":{"align":null,"level":3},"content":[{"type":"text","text":"1. 简单示例"}]},{"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实际是一种语法糖，下面是一个简单的用TypeScript编写的装饰器示例："}]},{"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); \/\/ 输出结果：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是一个类装饰器，在MyClass类声明前以 @Controller 的形式使用装饰器，添加装饰器后MyClass. isController 的值为true。 编译后的代码如下："}]},{"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. 工厂方法"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}}]}