meteor-methods

Meteor methods

Methods are Meteor's primitive for server-side mutation called from the client. In Meteor 3 they are async on the server. Latency compensation still works via client-side stubs.

Decision flow

1. Is this code mutating server data? Use a method.
2. Does the client need to read the result before the server replies? Write a client stub with the same name; it mutates the local Minimongo collection and the change is reverted if the server disagrees.
3. Does the method accept untrusted input? Validate every argument with check(). Otherwise the agent should refuse to write the method.
4. Is the method rate-sensitive? Add a DDPRateLimiter.addRule.

Scaffold

import { Meteor } from "meteor/meteor";
import { check, Match } from "meteor/check";

Meteor.methods({
  async addItem(payload) {
    check(payload, {
      title: String,
      qty: Match.Integer,
    });
    if (!this.userId) {
      throw new Meteor.Error("not-authorized");
    }
    const _id = await Items.insertAsync({
      ...payload,
      ownerId: this.userId,
      createdAt: new Date(),
    });
    return _id;
  },
});

Calling from the client

try {
  const id = await Meteor.callAsync("addItem", { title: "Hi", qty: 1 });
  setLocalId(id);
} catch (err) {
  if (err && typeof err === "object" && "error" in err) {
    console.error(err.error, err.reason, err.details);
  } else {
    console.error("local or transport failure", err);
  }
}

Optimistic UI

Define the same method on the client. The client stub runs immediately against the local Minimongo; the server's authoritative result reverts any divergence.

// client/methods.js
import { Meteor } from "meteor/meteor";
import { Random } from "meteor/random";
Meteor.methods({
  addItem(payload) {
    Items.insert({
      ...payload,
      _id: Random.id(),
      ownerId: Meteor.userId(),
      createdAt: new Date(),
    });
  },
});

Synchronous stubs are simplest when they only need synchronous Minimongo. Async stubs are also supported by callAsync and are useful when the same method definition runs on client and server with *Async collection calls. An async stub may await microtask-based local work, but it must not wait on fetch, timers, IndexedDB, workers, or other browser macrotask APIs. Run external I/O outside the stub.