前置知识

控制反转与依赖注入

一般写法

class A {
  name: string;

  // constructor() {
  //     this.name = "A";
  // }

  // 当构造函数增加参数时，创建实例时必须传入参数，否则会报错，出现了强耦合的问题
  constructor(name: string) {
    this.name = name;
  }
}

class B {
  a: string;

  constructor() {
    this.a = new A().name; // 报错
  }
}

class C {
  a: string;

  constructor() {
    this.a = new A().name; // 报错
  }
}

引入控制反转和依赖注入

class A {
  name: string;

  constructor(name: string) {
    this.name = name;
  }
}

class B {
  name: string;

  constructor(name: string) {
    this.name = name;
  }
}

// 依赖注入容器
class Container {
  module: any;

  constructor() {
    this.module = {};
  }

  provide(key: string, mo: any) {
    this.module[key] = mo;
  }

  get(key: string) {
    return this.module[key];
  }
}

// 创建容器实例
const c1 = new Container();
// 注册依赖
c1.provide("A", new A("Alice"));
c1.provide("B", new B("Bob"));

console.log(c1.get("A").name);
console.log(c1.get("B").name);

class X {
  a: any;
  b: any;

  constructor(mo: Container) {
    this.a = mo.get("A");
    this.b = mo.get("B");
  }
}

装饰器

配置

$ tsc --init

tsconfig.json

{
  "compilerOptions": {
    "experimentalDecorators": true
  }
}

类装饰器

const doc: ClassDecorator = (targe: any) => {
  console.log("ClassDecorator called on: ", target);
  target.prototype.name = "Class A";
};

// 类装饰器
@doc
class A {
  constructor() {}
}

const a1: any = new A();
console.log(a1.name);

属性装饰器

const doc: PropertyDecorator = (target: any, propertyKey: string | symbol) => {
  console.log("PropertyDecorator called on: ", target, propertyKey);
};

class A {
  // 属性装饰器
  @doc
  public name: string;

  constructor() {
    this.name = "Class A";
  }
}

方法装饰器

const doc: PropertyDecorator = (
  target: any,
  propertyKey: string | symbol,
  descriptor: any,
) => {
  console.log(target, propertyKey, descriptor);
};

class A {
  public name: string;

  constructor() {
    this.name = "Class A";
  }

  @doc
  getName() {}
}

参数装饰器

const doc: ParameterDecorator = (
  target: any,
  propertyKey: string | symbol | undefined,
  parameterIndex: number,
) => {
  console.log(target, propertyKey, parameterIndex);
};

class A {
  public name: string;

  constructor() {
    this.name = "Class A";
  }

  getName(name: string, @doc age: number) {}
}

装饰器实现NestJS底层GET

import axios from "axios";

const Get = (url: string) => {
  return (target: any, key: any, descriptor: PropertyDecorator) => {
    const fn = descriptor.value;
    axios
      .get(url)
      .then((res) => {
        fn(res, {
          status: 200,
          success: true,
        });
      })
      .catch((e) => {
        fn(res, {
          status: 500,
          success: false,
        });
      });
  };
};

class Controller {
  constructor() {}

  @Get("/list")
  getList(res: any, status: any) {
    console.log(res.data, status);
  }
}