Firebase Collection

Documentation

An element wrapper for the Firebase API that provides a view into the provided Firebase location as an ordered collection.

By default, Firebase yields values as unsorted document objects, where each of the children are accessible via object keys. The <firebase-collection> element allows Firebase API orderBy, limitTo and other query-oriented methods to be specified declaratively. The element then produces and maintains an Array of ordered child items of the document that is convenient for iterating over in other elements such as <template is="dom-repeat">.

Example:

  <template is="dom-bind">
    <firebase-collection
      order-by-child="height"
      limit-to-first="3"
      location="https://dinosaur-facts.firebaseio.com/dinosaurs"
      data="{{dinosaurs}}"></firebase-collection>
    <template is="dom-repeat" items="[[dinosaurs]]" as="dinosaur">
      <h4>[[dinosaur.__firebaseKey__]]</h4>
      <span>Height: </span><span>[[dinosaur.height]]</span><span>m</span>
    </template>
  </template>

As you may have noticed above, the original key of each item is available as the__firebaseKey__ property on the item.

The element makes special accomodations for documents whose children are primitive values. A primitive value is wrapped in an object with the form:

{
  value: /* original primitive value */
  __firebaseKey__: /* key of primitive value in parent document */
}

Accessor methods such as add and remove are provided to enable convenient manipulation of the collection without direct knowledge of Firebase key values.

API Reference

SHOW PRIVATE API

Properties

data

Arraydefault: [] readOnly notify

An ordered array of data items produced by the current Firebase Query instance.

endAt

Stringdefault:

Specify an end record for the set of records reflected in the collection.

equalTo

Stringdefault:

Specify to create a query which includes children which match the specified value. The argument type depends on which orderBy() function was used in this query. Specify a value that matches the orderBy() type.

limitToFirst

Numberdefault:

Specify a maximum number of records reflected on the client limited to the first certain number of children.

limitToLast

Numberdefault:

Specify a maximum number of records reflected on the client limited to the last certain number of children.

orderByChild

Stringdefault:

Specify a child key to order the set of records reflected on the client.

orderByKey

Booleandefault: false

Specify to order by key the set of records reflected on the client.

orderByPriority

Booleandefault: false

Specify to order by priority the set of records reflected on the client.

orderByValue

Booleandefault: false

Specify to order by value the set of records reflected on the client.

orderValueType

Stringdefault: string

Specify to override the type used when deserializing the value of start-at, end-at and equal-to attributes. By default, these values are always deserialized as String, but sometimes it is preferrable to deserialize these values as e.g., Number.

Accepted values for this attribute, and their corresponding deserialization types, are as follows:

• string => String (default)
• number => Number
• boolean => Boolean

query

Object notify

A pointer to the current Firebase Query instance being used to populatedata.

startAt

Stringdefault:

Specify a start record for the set of records reflected in the collection.

Methods

add(data) ➙ Object

1. data Object 
   A value to add to the document.
2. Returns Object
   A Firebase Query instance referring to the added item.

Add an item to the document referenced at location. A key associated with the item will be created by Firebase, and can be accessed via the Firebase Query instance returned by this method.

getByKey(key)

1. key String
   The key associated with the item in the parent document.

Look up an item in the local data Array by key.

remove(data)

1. data Object 
   An identical reference to an item in this.data.

Remove an item from the document referenced at location. The item is assumed to be an identical reference to an item already in the dataArray.

removeByKey(key)

1. key String
   The key associated with the item in the document located at location.

Remove an item from the document associated with location by key.

Behaviors

Polymer.FirebaseQueryBehavior

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