trilogy

# Lifecycle hooks

Hooks are triggered by specific events throughout trilogy's lifecycle that you can tap into in order to fire off your own actions. There are both pre- and post-event hooks for object creation, updates, and removals, as well as an onQuery hook that's called on each SQL query.

TIP

It's important to be aware of the fact that methods such as increment, decrement, and set will not trigger update hooks because they only modify a property and not a record as a whole. The hook would therefore not be useful since you could not reliably identify records.

These hooks can all be attached to a Trilogy instance or scoped more specifically to a particular Model. You could for example add a beforeUpdate hook to a model that sets the updated_at timestamp whenever an object is updated:

import { connect } from 'trilogy'

const db = connect('./storage.db')

;(async () => {
  const users = await db.model('users', {
    name: String
  }, {
    timestamps: true
  })

  users.beforeUpdate(item => {
    item.updated_at = new Date()
  })

  await users.create({ name: 'mr. robot' })
})()

# preventing events

In the case of the before* hooks, it's also possible to cancel the upcoming event from any subscriber to that hook. For example, in a beforeCreate hook:

import { connect, EventCancellation } from 'trilogy'

const db = connect(':memory:')

db.model('users', {
  name: String,
  isAdmin: Boolean
}).then(users => {
  const unsub = users.beforeCreate(user => {
    if (user.isAdmin && user.name !== 'boss') {
      // boss is the only admin allowed apparently
      return EventCancellation
    }
  })
})

# available hooks

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