next.js/examples/with-mobx-state-tree-typescript/stores/store.ts

import { applySnapshot, Instance, SnapshotIn, SnapshotOut, types } from "mobx-state-tree";

let store:IStore = null as any;

const Store = types
  .model({
    foo: types.number,
    lastUpdate: types.Date,
    light: false,
  })
  .actions((self) => {
    let timer;
    const start = () => {
      timer = setInterval(() => {
        // mobx-state-tree doesn't allow anonymous callbacks changing data.
        // Pass off to another action instead (need to cast self as any
        // because typescript doesn't yet know about the actions we're
        // adding to self here)
        (self as any).update();
      }, 1000);
    };
    const update = () => {
      self.lastUpdate = new Date(Date.now());
      self.light = true;
    };
    const stop = () => {
      clearInterval(timer);
    };
    return { start, stop, update };
  });

type IStore = Instance<typeof Store>;
type IStoreSnapshotIn = SnapshotIn<typeof Store>;
type IStoreSnapshotOut = SnapshotOut<typeof Store>;

const initializeStore = (isServer, snapshot = null) => {
  if (isServer) {
    store = Store.create({ foo:6, lastUpdate: Date.now() });
  }
  if (store as any === null) {
    store = Store.create({ foo:6, lastUpdate: Date.now() });
  }
  if (snapshot) {
    applySnapshot(store, snapshot);
  }
  return store;
};

export { initializeStore, IStore, IStoreSnapshotIn, IStoreSnapshotOut };