Hey everyone!
I'm back, and with a little bit more confidence πͺ. I am also very grateful for the encouragement I got from the previous post. Thank you!
In Part one: Basic react-query setup, we talked about how to quickly setup react-query
in our react project. We also touched on QueryClientProvider
component, queryClient
, ReactQueryDevtools
component and queryClient config object queryClientConfig
.
This will be a fairly long post. So, please use the links below to skip to sections relevant to you.
Table of contents
Intro
In this part, we will briefly talk about the configurations settings object queryClientConfig
we saw earlier. We will also look at what each key-value pair in the configuration does for our queries and mutations.
The QueryClient configuration
You remember this snippet from the last post ?
import { QueryClient, QueryClientProvider } from 'react-query';
const queryClientConfig = {
defaultOptions: {
queries: {
retry: 2,
staleTime: 1000 * 30,// 30seconds
cacheTime: 1000 * 30, //30 seconds
refetchOnMount: "always",
refetchOnWindowFocus: "always",
refetchOnReconnect: "always",
refetchInterval: 1000 * 30, //30 seconds
refetchIntervalInBackground: false,
suspense: false,
},
mutations: {
retry: 2,
},
},
...
The queryClientConfig
object provides us with the ability to tweak and override the default behavior of react-query
library or to put it better; it enables us create our custom defaults both for queries and mutations across our application. This global configuration can also be overridden for each query or mutation instance in our application if need be (We will see how in the next article). Nested in the queryClientConfig
object, is the defaultOptions
object, which in turn has two objects; queries
and mutations
nested in it. The key-value pairs in these two objects(queries
and mutations
) are what we will be talking about.
queries
The queries
object lets us configure react-query
behavior for our queries. According to the documentation, queries
can be passed in more configuration options but I chose this bit to keep things simple and flexible, also I believe they are the most relevant for the scope of this article.
retry
The retry
option takes either a boolean
, number
or function
as it's value. When false
, our unsuccessful queries are not retried by default.
Passing in a true
value ensures that our queries are retried infinitely (i.e. continued retries until the query gets successful).
When retry
is given a number
value, failed queries will retry until the failed queries count meets that number.
retry
do also take a function
as it's value. This function
receives a failure count(number) and error as it's first and second argument respectively. This function
must return a boolean
to determine whether a query should be retried or not.
...
//function as value for retry
const queryClientConfig = {
defaultOptions: {
queries: {
retry: (failureCount, error) => {
//...do something with passed argument
}
...
},
},
...
function
as a value of retry
is aimed at giving us more granular control to determine ourselves if a query should be retried based on the number of failed attempts, type of error or both.
staleTime
staleTime
is time in milliseconds after which the returned data from a successful query is considered stale. staleTime
accepts either a number
or Infinity
as it's value. Infinity
as a value ensures that our data is never considered stale. When staleTime
receives a number
, the number
is calculated as time in milliseconds after which the data is considered stale.
cacheTime
The cacheTime
options receives either a number
or Infinity
as a value. It is the time in milliseconds that an unused/inactive cached data is allowed to remain in memory. When a cached data becomes unused or inactive, it will be cleaned-up from the memory after this duration. When different cache times are specified, the longest one will be used.
If cacheTime
is set to Infinity, cached data are never cleaned from memory.
When cacheTime
receives a number
as it's value, this number is calculated as time in milliseconds after which, inactive/unused cached data is purged from memory.
refetchOnMount
When a component mounts and a query is run for the first time, the returned data from this successful query is cached. Sometimes, we may not want this same query to run again if the component remounts and the returned data from the previous call is still exists and fresh in the cache; this is the control refetchOnMount
gives us.
refetchOnMount
accepts a boolean
or the string
: "always"
as it's value.
If set to false
, the query will not refetch on component mount by default.
If value is set to true
, the query is refetched if the data in cache is considered stale.
"always"
as it's value will ensure that query is refetched regardless of whether cached data is stale or not.
(Refer to staleTime
to know when data is considered stale).
refetchOnWindowFocus
This option is similar to refetchOnMount
but for window focus.
We may wish to show our users fresh data whenever they switch their focus back to the browser tab where our application is being used; refetchOnWindowFocus
helps with this.
It accepts similar values as refetchOnMount
: boolean
or the string
,"always"
.
When refetchOnWindowFocus
is set to false
, query will not be refetched on window focus. When set to true
, query is refetched only if cached data is stale. "always"
will cause queries to refetch regardless of whether cached data is stale or not.
refetchOnReconnect
While using our application, users may lose internet connection. During this period, long or short as it may be, remote data may have changed.
refetchOnReconnect
gives use the control to determine whether we want our application to refetch queries once our users regain internet connection.
refetchOnReconnect
accepts a boolean
or the string
, "always"
. By now, you can guess where this is going π.
With false
as a value, queries are not refetched on reconnection to the internet at all.
true
lets queries refetch on reconnection only if the data is considered stale. (again, check staleTime
to understand when a cached data is considered stale).
"always"
will ensure queries are refetched whether cached data is stale or not.
refetchInterval
We may want our application refetching queries at certain interval in time regardless of whether data is stale or not. This is very useful for rapidly changing remote data or for near real-time behavior for our application.
refetchInterval
accepts either false
or a number
as it's value.
false
means that our queries will not refetch at interval.
When a number
is passed to refetchInterval
as a value, this number is calculated as time in milliseconds. For example, 5000 as a value of refetchInterval
means queries will be refetched every 5 seconds.
refetchIntervalInBackground
Would you like explicitly control the refetchInterval
behavior for when users are not focused on our application ?refetchIntervalInBackground
lets us do this. It accepts only boolean
values.
true
as a value implies that queries will be refetched at interval (as set on refetchInterval
) even when our application is not in focus. When false
, queries will not refetch at interval when our application is not in focus.
suspense
suspense
accepts only boolean
values.
When set to true
, active queries will suspend and will throw a runtime error if an error occurs.
With false
, active queries will neither suspend nor throw a runtime error if an error occurs.
mutations
Pheew π€ if you have gotten this far, I'm grateful. I'm a little π© myself. Hang in there, we are almost done.
The mutations
object lets us configure react-query
behavior for our mutations. Mutations are for create/update/delete actions to our server. For any action that seeks to mutate our remote data, mutations
should be used. Lets discuss the only item in the mutations
object: retry
.
retry
retry
as an option for the mutations
object is similar to that for queries
.
retry
accepts either a boolean
, number
or function
as it's value.
false
as the value for retry
ensures that failed mutations will not retry by default.
When true
, failed mutations will retry infinitively(i.e. until a mutation is successful).
If set to an number
, e.g. 3, failed mutations will retry until the failed mutations count meets that number.
function
as a value for retry
enables us decide ourselves, when we want failed mutations to retry. This function
must return a boolean
.
...
//function as value for retry in mutations
const queryClientConfig = {
defaultOptions: {
...
mutations: {
retry: (failureCount, error) => {
//...do something with passed argument
}
},
},
...
Conclusion
This post was a long one and I really appreciate that you made it this far.
In the next part, we will discuss data fetching with the useQuery hook.
Thank you all for your support. Please give me a π if this post or part of it has helped you. Comments are welcomed too.
Follow me on twitter @NnajioforEmma10
Credits
Image: Logrocket: What is new in react-query 3 by Lawrence Eagles.
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