Class Retainer

Example

import {Retainer, sleep} from "lifecycle-utils";

class MyClass {
    private _retainer = new Retainer();

    async useResource() {
        using handle = this._retainer.tryRetain(() => new Error("Resource is draining"));

        console.log("using resource");
        await sleep(1000);
        console.log("done using resource");
    }

    async drain() {
        console.log("awaiting drain");
        using drain = await this._retainer.acquireDrain();

        // no retained usages are active while the drain handle is held
        console.log("drain started");
        await sleep(1000);
    }
}

const myClass = new MyClass();

const usePromise = myClass.useResource();
const drainPromise = myClass.drain();

await myClass.useResource().catch(console.log);
await Promise.all([usePromise, drainPromise]);

// using resource
// awaiting drain
// Error: Resource is draining
// done using resource
// drain started
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