Configuration options
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These can be passed in an object to useAsync(options)
, or as props to <Async {...options}>
and custom instances.
An already started Promise instance.
Function that returns a Promise, automatically invoked.
Function that returns a Promise, manually invoked with run
.
Watch a value and automatically reload when it changes.
Watch this function and automatically reload when it returns truthy.
Provide initial data or error for server-side rendering.
Callback invoked when Promise resolves.
Callback invoked when Promise rejects.
Callback invoked when a Promise is cancelled.
State reducer to control internal state updates.
Action dispatcher to control internal action dispatching.
Unique label used in DevTools.
Enable experimental Suspense integration.
useFetch
additionally takes these options:
Force the use of deferFn
or promiseFn
.
Enable JSON parsing of the response.
promise
Promise
A Promise instance which has already started. It will simply add the necessary resolve/reject callbacks and set startedAt
to the time promise
was first provided. Changing the value of promise
will cancel any pending promise and listen to the new one. If promise
is initially undefined, the React Async state will be pending
.
Note that
reload
will not do anything when usingpromise
. UsepromiseFn
instead.
promiseFn
function(props: Object, controller: AbortController): Promise
A function that returns a promise. It is automatically invoked in componentDidMount
and componentDidUpdate
. The function receives all component props (or options) and an AbortController instance as arguments.
deferFn
function(args: any[], props: Object, controller: AbortController): Promise
A function that returns a promise. This is invoked only by manually calling run(...args)
. Any arguments to run
are passed-through as an array via args
, so you can pass data through either args
or props
, as needed. The deferFn
is commonly used to send data to the server following a user action, such as submitting a form. You can use this in conjunction with promiseFn
to fill the form with existing data, then updating it on submit with deferFn
.
Be aware that when using both
promiseFn
anddeferFn
, the shape of their fulfilled value should match, because they both update the samedata
.
watch
any
Watches this property through componentDidUpdate
and re-runs the promiseFn
when the value changes, using a simple reference check (oldValue !== newValue
). If you need a more complex update check, use watchFn
instead.
watchFn
function(props: Object, prevProps: Object): boolean | any
Re-runs the promiseFn
when this callback returns truthy (called on every update). Any default props specified by createInstance
are available too.
initialValue
any | Error
Initial state for data
or error
(if instance of Error); useful for server-side rendering. When an initialValue
is provided, the promiseFn
will not be invoked on first render. Instead, status
will be immediately set to fulfilled
or rejected
and your components will render accordingly. If you want to trigger the promiseFn
regardless, you can call reload()
or use the watch
or watchFn
option.
Note that
onResolve
oronReject
is not invoked in this case and nopromise
prop will be created.
onResolve
function(data: any): void
Callback function invoked when a promise resolves, receives data as argument.
onReject
function(reason: Error): void
Callback function invoked when a promise rejects, receives rejection reason (error) as argument.
onCancel
function(): void
Callback function invoked when a promise is cancelled, either manually using cancel()
or automatically due to props changes or unmounting.
reducer
function(state: any, action: Object, internalReducer: function(state: any, action: Object))
dispatcher
function(action: Object, internalDispatch: function(action: Object), props: Object)
Action dispatcher to take full control over action dispatching by wrapping the internal dispatcher. It receives the original action, the internal dispatcher and all component props (or options). You probably want to invoke the internal dispatcher at some point.
debugLabel
string
A unique label to describe this React Async instance, used in React DevTools (through useDebugValue
) and React Async DevTools.
suspense
boolean
Enables experimental Suspense integration. This will make React Async throw a promise while loading, so you can use Suspense to render a fallback UI, instead of using <IfPending>
. Suspense differs in 2 main ways:
<Suspense>
should be an ancestor of your Async component, instead of a descendant. It can be anywhere up in the
component hierarchy.
You can have a single <Suspense>
wrap multiple Async components, in which case it will render the fallback UI until
all promises are settled.
Note that the way Suspense is integrated right now may change. Until Suspense for data fetching is officially released, we may make breaking changes to its integration in React Async in a minor or patch release. Among other things, we'll probably add a cache of sorts.
defer
boolean
Enables the use of deferFn
if true
, or enables the use of promiseFn
if false
. By default this is automatically chosen based on the request method (deferFn
for POST / PUT / PATCH / DELETE, promiseFn
otherwise).
json
boolean
Enables or disables JSON parsing of the response body. By default this is automatically enabled if the Accept
header is set to "application/json"
.
Be aware that updating promiseFn
will trigger it to cancel any pending promise and load the new promise. Passing an inline (arrow) function will cause it to change and reload on every render of the parent component. You can avoid this by defining the promiseFn
value outside of the render method. If you need to pass variables to the promiseFn
, pass them as additional props to <Async>
, as promiseFn
will be invoked with these props. Alternatively you can use useCallback
or to avoid unnecessary updates.
State reducer to take full control over state updates by wrapping the . It receives the current state, the dispatched action and the internal reducer. You probably want to invoke the internal reducer at some point.
This is a power feature which loosely follows the . It allows you to control state changes by intercepting actions before they are handled, or by overriding or enhancing the reducer itself.
This is a power feature similar to the . It allows you to control state changes by intercepting actions before they are dispatched, to dispatch additional actions, possibly later in time.