Queries

Creating

Firebase Real Time Database queries can be created in two ways:

  • Manually - Using watchEvents or watchEvent (requires managing of listeners)
  • Automatically - Using firebaseConnect HOC (manages mounting/unmounting)

Manually

Queries can be created manually by using watchEvent or watchEvents. This is useful to load data on some event such as a button click.

import React from 'react'
import PropTypes from 'prop-types'
import { connect } from 'react-redux'
import { compose } from 'redux'
import { withFirebase, isLoaded, isEmpty } from 'react-redux-firebase'

const Todos = ({ firebase }) => {
  // Build Todos list if todos exist and are loaded
  const todosList = !isLoaded(todos)
    ? 'Loading'
    : isEmpty(todos)
      ? 'Todo list is empty'
      : Object.keys(todos).map(
          (key, id) => <TodoItem key={key} id={id} todo={todos[key]}/>
        )
  return (
    <div>
      <h1>Todos</h1>
      <ul>
        {todosList}
      </ul>
      <button onClick={() => firebase.watchEvent('value', 'todos')}>
        Load Todos
      </button>
    </div>
  )
}

export default compose(
  withFirebase, // or firebaseConnect()
  connect(
    (state) => ({
      todos: state.firebase.data.todos,
      // profile: state.firebase.profile // load profile
    })
  )
)(Todos)

Though doing things manually is great to understand what is going on, it comes with the need to manage these listeners yourself.

Fun Fact - firebaseConnect actually calls watchEvents internally on component mount/unmount and when props change.

Automatically

firebaseConnect accepts an array of paths for which to create queries. When listening to paths, it is possible to modify the query with any of Firebase's included query methods.

The results of the queries created by firebaseConnect are written into redux state under the path of the query for both state.firebase.ordered and state.firebase.data.

NOTE:

By default the results of queries are stored in redux under the path of the query. If you would like to change where the query results are stored in redux, use storeAs (more below).

Ordered vs Data (by key)

data

In order to get data from state by key, use data.

Examples

  1. Get an object of projects by key
compose(
  firebaseConnect(props => [
    { path: 'projects' }
  ]),
  connect((state, props) => ({
    projects: state.firebase.data.projects,
  }))
)

ordered

In order to get ordered data, use orderedToJS

Examples

  1. Get list of projects ordered by key
compose(
  firebaseConnect(props => [
    { path: 'projects', queryParams: ['orderByKey'] }
  ]),
  connect((state, props) => ({
    projects: state.firebase.ordered.projects,
  }))
)

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.

Visit Populate Section for full documentation.

Types of Queries

There are multiple types of queries

once

To load a firebase location once instead of binding, the once option can be used:

Internally Uses Firebase Method: orderByPriority

firebaseConnect([
  { type: 'once', path: '/todos' }
])

Query Params

Note: orderByChild, orderByValue, and orderByPriority enable automatic parsing of query params that follow them for convince. This means that the order of query params can affect which query is created. For example:

// Works since limitToFirst and startAt are parsed into numbers
queryParams: [`limitToFirst=${limitToFirst}`, `startAt=${startAt}`, 'orderByValue'],

// COULD CAUSE UNEXPECTED BEHAVIOR!!! Values passed to limitToFirst and startAt will remain as strings (i.e not parsed)
queryParams: ['orderByValue', `limitToFirst=${limitToFirst}`, `startAt=${startAt}`],

If you would like to prevent or cause parsing of query params yourself, you can pass notParsed or parsed as a queryParam:

// limitToFirst and startAt remain as strings and are NOT automatically parsed
queryParams: ['notParsed', `limitToFirst=${limitToFirst}`, `startAt=${startAt}`, 'orderByValue'],
// limitToFirst and startAt are parsed into numbers if possible
queryParams: ['parsed', `limitToFirst=${limitToFirst}`, `startAt=${startAt}`, 'orderByValue'],

More on notParsed below

orderByChild

To order the query by a child within each object, use orderByChild.

Internally Uses Firebase Method: orderByChild

Example

Ordering a list of todos by the text parameter of the todo item (placing them in alphabetical order).

firebaseConnect([
  { path: '/todos', queryParams: [ 'orderByChild=text' ]}
  '/todos#orderByChild=text' // string notation
])

orderByKey

Order a list by the key of each item. Since push keys contain time, this is also a way of ordering by when items were created.

Internally Uses Firebase Method: orderByKey

Example

Ordering a list of todos based on their key (puts them in order of when they were created)

firebaseConnect([
  { path: '/todos', queryParams: [ 'orderByKey' ]}
  // '/todos#orderByKey' // string notation
])

orderByValue

Order a list by the value of each object. Internally runs

Internally Uses Firebase Method: orderByValue

Example

Ordering a list of score's based on score's value

firebaseConnect([
  { path: '/scores', queryParams: [ 'orderByValue' ] }
  // `scores#orderByValue` // string notation
])

orderByPriority

Order a list by the priority of each item.

Internally Uses Firebase Method: orderByPriority

Example

Ordering a list based on priorities

firebaseConnect([
  { path: '/scores', queryParams: [ 'orderByPriority' ] }
  // `scores#orderByPriority` // string notation
])

limitToFirst

Limit query results to the first n number of results.

Internally Uses Firebase Method: limitToFirst

Examples

  1. Displaying only the first todo item

    firebaseConnect([
 { path: '/todos', queryParams: [ 'limitToFirst=1' ] }
 // '/todos#limitToFirst' // string notation
])

  2. Displaying only the first 10 todo items

    firebaseConnect([
 { path: '/todos', queryParams: [ 'orderByChild=createdBy', 'equalTo=123' ] }
 // '/todos#limitToFirst=10' // string notation
])

limitToLast

Limit query results to the last n number of results

Internally Uses Firebase Method: limitToLast

Examples

  1. Only the last todo item

    firebaseConnect([
 { path: '/todos', queryParams: [ 'limitToLast' ] }
 // '/todos#limitToLast' // string notation
])

  2. Only the last 10 todo items

    firebaseConnect([
 { path: '/todos', queryParams: [ 'limitToLast=10' ] }
 // '/todos#limitToLast=10' // string notation
])

startAt

Start query at a specific location by providing the specific number or value

Internally Uses Firebase Method: startAt

Examples

  1. Starting at the fifth item
    firebaseConnect([
 { path: '/todos', queryParams: [ 'startAt=5', 'limitToFirst=2' ] }
 // 'todos#startAt=5&limitToFirst=2' // string notation
])
  2. Paginate results
    firebaseConnect([
 { path: '/todos', queryParams: [ 'startAt=5', 'limitToFirst=10' ] }
 // 'todos#startAt=5&limitToFirst=10' // string notation
])
  3. Non-number values
    firebaseConnect([
{ path: '/todos', queryParams: [ 'startAt=5', 'limitToFirst=10' ] }
// 'todos#startAt=val1&limitToFirst=10' // string notation
])(SomeComponent)

endAt

End query at a specific location by providing the specific number or value

Internally Uses Firebase Method: endAt

Examples

  1. Usage with startAt
    firebaseConnect([
{ path: '/todos', queryParams: [ 'orderByChild=added', 'startAt=1', 'endAt=5' ] }
// 'todos#orderByChild=added&startAt=1&endAt=5' // string notation
])

equalTo

Limit query results with parameter equal to previous query method (i.e when used with orderByChild, it limits results with child equal to provided value).

Internally Uses Firebase Method: equalTo

Parsing

The following are internally parsed:

  • null
  • boolean
  • number

This means the actual value will be parsed instead of the string containing the value. If you do not want this to happen, look at the notParsed query parameter below.

Examples

  1. Order by child parameter
    firebaseConnect([
{ path: '/todos', queryParams: [ 'orderByChild=createdBy', 'equalTo=ASD123' ] }
// 'todos#orderByChild=createdBy&equalTo=ASD123', // string notation
])

notParsed

Can be used to keep internal parsing from happening. Useful when attempting to search a number string using equalTo

Examples

  1. Order by child parameter equal to a number string. Equivalent of searching for '123' (where as not using notParsed would search for children equal to 123)
    firebaseConnect([
{
 path: '/todos',
 queryParams: [
   'orderByChild=createdBy',
   'notParsed', // keeps equalTo from automatically parsing
   'equalTo=123'
 ]
}
])

parsed

Internally parse following query params. Useful when attempting to parse

NOTE: orderByChild, orderByPriority, and orderByValue will cause this to be enabled by default. Parsing will remain enabled for the rest of the query params until notParsed is called.

Added as part of v2.0.0-beta.17

Examples

  1. Order by child parameter equal to a number string. Equivalent of searching for '123' (where as not using notParsed would search for children equal to 123) 

    firebaseConnect([
 {
   path: '/todos',
   queryParams: [
     'parsed', // causes automatic parsing
     'equalTo=123' // 123 is treated as a number instead of a string
     'orderByChild=createdBy',
   ]
 }
])

storeAs

By default the results of queries are stored in redux under the path of the query. If you would like to change where the query results are stored in redux, use storeAs.

Examples

  1. Querying the same path with different query parameters
const myProjectsReduxName = 'myProjects'

compose(
  firebaseConnect(props => [
    { path: 'projects' },
    {
      path: 'projects',
      storeAs: myProjectsReduxName,
      queryParams: ['orderByChild=uid', '123']
    }
  ]),
  connect((state, props) => ({
    projects: state.firebase.data.projects,
    myProjects: state.firebase.data[myProjectsReduxName], // use storeAs path to gather from redux
  }))
)

Why?

Data is stored in redux under the path of the query for convince. This means that two different queries to the same path (i.e. todos) will both place data into state.data.todos even if their query parameters are different.

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.

Visit Populate Section for full documentation.

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