Selectors

While it is possible to get a remote state from requestsReducer on your own, it is recommented to use below selectors. For one thing, they are already optimized, reusing cache and clearing it when necessary. Another reason is that they return only information needed by applications, while state kept in requestsReducer contains more data required by the library itself. Not to mention a situation when you use automatic normalisation. Data in reducer is kept normalized, while you need it denormalized in your apps. Selectors already know how to denormalize it automatically and quickly, so that you don't even need to worry about it.

getQuery

getQuery is a selector which returns a state for a given query. It is the selector which requires props. Imagine you want to get a state for FETCH_BOOKS query which we played with earlier. You can use it like this:

import { getQuery } from '@redux-requests/core';

const booksQuery = getQuery(state, { type: 'FETCH_BOOKS' });
/* for example {
  data: [{ id: '1', name: 'Some book title' }],
  loading: false,
  error: null,
  pristine: false, // true only when there was no request made for a give type
  downloadProgress: null, // only when requestAction.meta.measureDownloadProgress is true
  uploadProgress: null, // only when requestAction.meta.measureUploadProgress is true
} */

If you are an experienced Redux developer, you might be worried about memoization of getQuery. Fear not! You can call it with different props and memoization is not lost, for example:

const booksQuery = getQuery(state, { type: 'FETCH_BOOKS' });
getQuery(state, { type: 'FETCH_STH_ELSE' });
booksQuery === getQuery(state, { type: 'FETCH_BOOKS' });
// returns true (unless state for FETCH_BOOKS query really changed in the meantime)

We only provided example for type prop, but here you have the list of all possibilities:

• type: string: just pass query action type or action itself when using action creator library
• requestKey: string: use it if you used meta.requestKey in query action
• multiple: set to true if you prefer data to be [] instead of null if data is empty, false by default
• defaultData: use it to represent data as an orbitrary object instead of null, use top level object though, not recreate it multiple times not to break selector memoization

getQuerySelector

It is almost the same as getQuery, the difference is that getQuery is the selector, while getQuerySelector is the selector creator - it just returns getQuery.

It is helpful when you need to provide a selector without props somewhere (like in useSelector React hook). So instead of doing useSelector(state => getQuery(state, { type: 'FETCH_BOOKS' })) you could just useSelector(getQuerySelector({ type: 'FETCH_BOOKS' })).

getMutation

Almost the same as getQuery, it is just used for mutations:

import { getMutation } from '@redux-requests/core';

const deleteBookMutation = getMutation(state, { type: 'DELETE_BOOK' });
/* for example {
  loading: false,
  error: null,
  downloadProgress: null, // only when requestAction.meta.measureDownloadProgress is true
  uploadProgress: null, // only when requestAction.meta.measureUploadProgress is true
} */

It accept type and optionally requestKey props, which work like for queries.

getMutationSelector

Like getQuerySelector, it just returns getMutation selector.