Module Middleware/Singleton

The singleton middleware let's you create a singleton object that will be shared between loaders of a single requests.

This is specially useful to share objects that needs to be created only once per request, like a cache, but not shared between requests.

import { unstable_createSingletonMiddleware } from "remix-utils/middleware/singleton";

export const [singletonMiddleware, getSingleton] =
  unstable_createSingletonMiddleware({
    instantiator: () => new MySingletonClass(),
  });
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To use it, you need to add it to the unstable_middleware array in the route where you want to use it.

import { singletonMiddleware } from "~/middleware/singleton.server";
export const unstable_middleware = [singletonMiddleware];
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And you can use the getSingleton function in your loaders to get the singleton object.

import { getSingleton } from "~/middleware/singleton.server";

export async function loader({ context }: LoaderFunctionArgs) {
  let singleton = getSingleton(context);
  let result = await singleton.method();
  // ...
}
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The singleton middleware can be created with different classes and arguments, so you can have multiple singletons in the same request.

import { unstable_createSingletonMiddleware } from "remix-utils/middleware/singleton";

export const [singletonMiddleware, getSingleton] =
  unstable_createSingletonMiddleware({
    instantiator: () => new MySingletonClass("arg1", "arg2"),
  });

export const [anotherSingletonMiddleware, getAnotherSingleton] =
  unstable_createSingletonMiddleware({
    instantiator: () => new AnotherSingletonClass("arg1", "arg2"),
  });
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And use it in a route like this.

import {
  singletonMiddleware,
  anotherSingletonMiddleware,
} from "~/middleware/singleton.server";

export const unstable_middleware = [
  singletonMiddleware,
  anotherSingletonMiddleware,
];
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You can also access the request and context objects in the instantiator function, so you can create the singleton based on the request or context.

import { unstable_createSingletonMiddleware } from "remix-utils/middleware/singleton";
import { MySingletonClass } from "~/singleton";

export const [singletonMiddleware, getSingleton] =
  unstable_createSingletonMiddleware({
    instantiator: (request, context) => {
      return new MySingletonClass(request, context);
    },
  });
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This can allows you to create a class that depends on the request, maybe to read the URL or body, or depends on the context, maybe to read the session or some other data.