Most React features should be usable from Reagent, even if Reagent doesn't provide functions to use them directly.
JSX:
function example() {
return (
<React.Fragment>
<ChildA />
<ChildB />
<ChildC />
</React.Fragment>
);
}
Reagent:
(defn example []
[:<>
[child-a]
[child-b]
[child-c]])
Reagent syntax follows React Fragment short syntax.
(defonce my-context (react/createContext "default"))
(def Provider (.-Provider my-context))
(def Consumer (.-Consumer my-context))
(rdom/render
[:> Provider {:value "bar"}
[:> Consumer {}
(fn [v]
(r/as-element [:div "Context: " v]))]]
container)
Context example project
better explains how
:>
or adapt-react-class
convert the properties to JS objects,
and shows how to use Cljs values with context.
Alternatively you can use the static contextType property
(defonce my-context (react/createContext "default"))
(def Provider (.-Provider my-context))
(defn show-context []
(r/create-class
{:context-type my-context
:reagent-render (fn []
[:p (.-context (reagent.core/current-component))])}))
;; Alternatively with metadata on a form-1 component:
;;
;; (def show-context
;; ^{:context-type my-context}
;; (fn []
;; [:p (.-context (reagent.core/current-component))]))
(rdom/render
[:> Provider {:value "bar"}
[show-context]]
container)
Tests contain example of using old React lifecycle Context API (context-wrapper
function):
tests
You can use getDerivedStateFromError
(since React 16.6.0 and Reagent 0.9) (and ComponentDidCatch
) lifecycle method with create-class
:
(defn error-boundary [comp]
(let [error (r/atom nil)]
(r/create-class
{:component-did-catch (fn [this e info])
:get-derived-state-from-error (fn [e]
(reset! error e)
#js {})
:reagent-render (fn [comp]
(if @error
[:div
"Something went wrong."
[:button {:on-click #(reset! error nil)} "Try again"]]
comp))})))
Alternatively, one could use React state instead of RAtom to keep track of error state, which
can be more obvious with the new getDerivedStateFromError
method:
(defn error-boundary [comp]
(r/create-class
{:constructor (fn [this props]
(set! (.-state this) #js {:error nil}))
:component-did-catch (fn [this e info])
:get-derived-state-from-error (fn [error] #js {:error error})
:render (fn [this]
(r/as-element
(if-let [error (.. this -state -error)]
[:div
"Something went wrong."
[:button {:on-click #(.setState this #js {:error nil})} "Try again"]]
comp)))}))
As per React docs, getDerivedStateFromError
is what should update the state
after error, it can be also used to update RAtom as in Reagent the Ratom is available
in function closure even for static methods. ComponentDidCatch
can be used
for side-effects, like logging the error.
JavaScript functions are valid React components, but Reagent implementation by default turns the ClojureScript functions referred in Hiccup-vectors to Class components.
However, some React features, like Hooks, only work with Functional components. There are several ways to use functions as components with Reagent:
Calling r/create-element
directly with a ClojureScript function doesn't
wrap the component in any Reagent wrappers, and will create functional components.
In this case you need to use r/as-element
inside the function to convert
Hiccup-style markup to elements, or just returns React Elements yourself.
You also can't use Ratoms here, as Ratom implementation requires the component
is wrapped by Reagent.
Using adapt-react-class
or :>
is also calls create-element
, but that
also does automatic conversion of ClojureScript parameters to JS objects,
which isn't usually desired if the component is ClojureScript function.
New way is to configure Reagent Hiccup-compiler to create functional components: Read Compiler documentation
NOTE: This section still refers to workaround using Hooks inside class components, read the previous section to create functional components.
Hooks can't be used inside class components, and Reagent implementation creates a class component from every function (i.e. Reagent component).
However, you can use React components using Hooks inside Reagent, or use
hx components inside Reagent. Also, it is
possible to create React components from Reagent quite easily, because React
function component is just a function that happens to return React elements,
and r/as-element
does just that:
;; This is React function component. Can't use Ratoms here!
(defn example []
(let [[count set-count] (react/useState 0)]
(r/as-element
[:div
[:p "You clicked " count " times"]
[:button
{:on-click #(set-count inc)}
"Click"]])))
;; Reagent component
(defn reagent-component []
[:div
;; Note :> to use a function as React component
[:> example]])
If you need to pass RAtom state into these components, dereference them in the Reagent components and pass the value (and if needed, function to update them) as properties into the React function component.
(defn reagent-component []
(let [el (.. js/document (getElementById "portal-el"))]
(react-dom/createPortal (r/as-element [:div "foo"]) el)))
(react-dom/hydrate (r/as-element [main-component]) container)
For interop with React libraries, you might need to pass Component classes to other components as parameter. If you have a Reagent component (a function) you can use r/reactify-component
which returns creates a Class from the function.
If the parent Component awaits classes with some custom methods or properties, you need to be careful and probably should use r/create-class
. In this case you don't want to use r/reactify-component
with a function (even if the function returns a class) because r/reactify-component
wraps the function in another Component class, and parent Component doesn't see the correct class.
;; Correct way
(def editor
(r/create-class
{:get-input-node (fn [this] ...)
:reagent-render (fn [] [:input ...])})))
[:> SomeComponent
{:editor-component editor}]
;; Often incorrect way
(defn editor [parameter]
(r/create-class
{:get-input-node (fn [this] ...)
:reagent-render (fn [] [:input ...])})))
[:> SomeComponent
{:editor-component (r/reactify-component editor)}]
In the latter case, :editor-component
is a Reagent wrapper class component, which doesn't have the getInputNode
method and is rendered using the Component created by create-class
and which has the method.
If you need to add static methods or properties, you need to modify create-class
return value yourself. The function handles the built-in static-methods (:childContextTypes :contextTypes :contextType :getDerivedStateFromProps :getDerivedStateFromError
), but not others.
(let [klass (r/create-class ...)]
(set! (.-static-property klass) "foobar")
(set! (.-static-method klass) (fn [param] ...))
klass)
Can you improve this documentation? These fine people already did:
Juho Teperi, David James Humphreys, Lucy Wang & Arne BrasseurEdit on GitHub
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