Populate

Populate allows you to replace IDs within your data with other data from Firebase. This is very useful when trying to keep your data flat. Some would call it a join, but it was modeled after the mongo populate method.

List of todo items where todo item can contain an owner parameter which is a user's UID like so:

{ text: 'Some Todo Item', owner: "Iq5b0qK2NtgggT6U3bU6iZRGyma2" }

Populate allows you to replace the owner parameter with another value on Firebase under that key. That value you can be a string (number and boolean treated as string), or an object

Example Data

todos: {
  123: {
    text: 'Some Todo Item',
    owner: "Iq5b0qK2NtgggT6U3bU6iZRGyma2"
   }
 }
 displayNames: {
   Iq5b0qK2NtgggT6U3bU6iZRGyma2: 'Scott Prue',
   6Ra53mf3U9Qmdwah6rXBMgY8smu1: 'Rick Sanchez'
 }
 users: {
   Iq5b0qK2NtgggT6U3bU6iZRGyma2: {
     displayName: 'Scott Prue',
     email: '[email protected]'
   },
   6Ra53mf3U9Qmdwah6rXBMgY8smu1: {
     displayName: 'Rick Sanchez',
     email: '[email protected]'
   }
 }

String, Number, or Boolean

When trying to replace the owner parameter with a string such as a displayName from a /displayNames root follow the pattern of #populate=paramToPopulate:populateRoot.

Example Query

@firebaseConnect([
  { path: '/todos', populates: [{ child: 'owner', root: 'displayNames' }] }
  // '/todos#populate=owner:displayNames', // equivalent string notation
 ])

Result

123: {
  text: 'Some Todo Item',
  owner: 'Scott Prue'
 }

Object

Population can also be used to populate a parameter with an object. An example of this would be populating the owner parameter, which is an ID, with the matching key from the users list.

Example Query

@firebaseConnect([
  { path: '/todos', populates: [{ child: 'owner', root: 'users' }] }
  // '/todos#populate=owner:users'// equivalent string notation
 ])

Example Result

123: {
  text: 'Some Todo Item',
  owner: {
    displayName: 'Scott Prue',
    email: '[email protected]'
  }
}

Object's Parameter

There is also the option to load a parameter from within a population object. An example of this could be populating the owner parameter with the displayName property of the user with a matching ID:

Example Query

@firebase([
 { path: '/todos', populates: [{ child: 'owner', root: 'users', childParam: 'email' }] }
 '/todos#populate=owner:users:email'
])

Example Result

123: {
  text: 'Some Todo Item',
  owner: '[email protected]'
}