06-persist-update-on-server.md

Side Effects: Persist Update to Server

Problem

You have finished the work on client side and need to persist some state on a server via an API

Solution

Use an orchestrator to call these service calls.

Discussion

Orchestrator is the only place within the SatchelJS library that allows for asynchronous calls. This is the perfect place to call into those network calls or asynchronous side effect function calls. Since orchestrators themselves cannot modify the state, it forces developers to separate coordination logic (business logic) from the store update logic. Just like the removeBookFromCart orchestrator from the previous recipe, the buy orchestrator coordinates the asynchronous "network call" makePurchase and various actions. One of the actions, finishBuying is subscribed by many mutators to complete the purchase flow. The new async / await pair of API provided by the newer browser & Typescript itself is a nice way to write these orchestrator:

orchestrator(buy, async() => {
    const store = getStore();
    beginBuying();
    await makePurchase(store.cart.books);
    finishBuying();
});