如何在 Tsyringe 中实现单例

Question

我在实现单例时遇到问题，因为标记为 @singleton() 的 class 在每次 resolve() 时都会重新创建。

示例如下

// Foo.ts This is singleton and and must be created only once
import { injectable, singleton } from "tsyringe";

@injectable()
@singleton()
export class Foo {
  constructor() {
    console.log("Constractor of Foo");
  }
}

// Bar.ts this is Bar and should be created every time. It uses the singleton
import { inject, injectable, Lifecycle, scoped } from "tsyringe";
import { Foo } from "./Foo";

@injectable()
export class Bar {
  constructor(@inject("Foo") private foo: Foo) {
    console.log("Constractor of Bar");
  }
}

// main.ts this is resolving Bar two times.
// expected output:
// Constractor of Foo
// Constractor of Bar
// Constractor of Bar

// Actual output:
// Constractor of Foo
// Constractor of Bar
// Constractor of Foo
// Constractor of Bar

import "reflect-metadata";
import { container } from "tsyringe";
import { Bar } from "./Bar";
import { Foo } from "./Foo";

container.register("Foo", { useClass: Foo });
container.register("Bar", { useClass: Bar });

const instance = container.resolve(Bar);
const instance1 = container.resolve(Bar);

如何获得所需的行为？

Answer 1

单例注册如下

container.register(
  "Foo",
  { useClass: Foo },
  { lifecycle: Lifecycle.Singleton } // <- this is important
);

Answer 2

我认为你让你的生活更加困难。我发现您所做的事情和您提出的解决方案有一些问题。这是 @singleton() 装饰器的 source code：

function singleton<T>(): (target: constructor<T>) => void {
  return function(target: constructor<T>): void {
    injectable()(target);
    globalContainer.registerSingleton(target);
  };
}

首先，你不需要用@injectable()装饰，因为tsyringe已经用@singleton().
最后，如果你不注册 Foo 和 Bar 它们将自动注册为单例（当然 { lifecycle: Lifecycle.Singleton } 选项已经设置）在 globalContainer.registerSingleton(target)函数。

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