transactionMiddleware

Overview

The transaction middleware makes a model action or flow atomic: if it throws, changes made during that action and its child actions are reverted before the error is rethrown.

Mark an action or flow as a transaction either with the @transaction decorator or by attaching transactionMiddleware programmatically.

As a decorator:

@model("MyApp/MyBalance")
class MyBalance extends Model({
  balance: prop<number>(),
}) {
  @transaction
  @modelAction
  addMoney(cents: number) {
    this.balance += cents
    // imagine that something else goes wrong
    // in this case balance will be reverted to the value that
    // was there before the action started
    throw new Error("...")
  }
}

Programmatically:

@model("MyApp/MyBalance")
class MyBalance extends Model({
  balance: prop<number>(),
}) {
  @modelAction
  addMoney(cents: number) {
    this.balance += cents
    // imagine that something else goes wrong
    // in this case balance will be reverted to the value that
    // was there before the action started
    throw new Error("...")
  }

  // we could for example add it on init (for all instances)
  onInit() {
    transactionMiddleware({
      model: this,
      actionName: "addMoney",
    })
  }
}

// or for a particular instance
const myBalance = new MyBalance({ balance: 100 })
transactionMiddleware({
  model: myBalance,
  actionName: "addMoney",
})

Overview​

Overview