reacl-c.core — de.active-group/reacl-c 0.11.1

Functions, primitive values and some macros to define new items.

add-state clj/s deprecated

(add-state initial lens item)

Adds new state that the given item can access, via a lens on the the tuple of states [outer inner], where the initial value for inner state is initial. Note that the resulting item has only outer as its state.

call clj/s

(call f & args)

Calls an event handler function f, which should be a function returned from calling the bind function of a with-bind item. Note that this returns a special return value, which you must return from another event handler, and which you can combine with local state changes via merge-returned.

CallHandler clj

cleanup clj/s

(cleanup f)

Returns an item that evaluates (f state) when it is being removed from the item tree, and emits the return value that that must return.

const-effect clj/s

(const-effect v)

Returns an effect that does nothing, with the given value as its result.

def-item clj/s macro

(def-item name & item)

A macro to define items. This is not much different than the standard def macro of Clojure, but it attaches the name of the var to the item, which can be helpful in testing and debugging utilities (see named).

(def-item submit-button
  (dom/button {:type "submit"}))

Additionally, a schema can be specified similar to [[core.schema/def]]. That schema does specify which state values are allowed for the defined item:

(def-item checkbox :- s/Bool
  (dom/input {:type "checkbox" ...}))

defn-effect clj/s macro

(defn-effect name args & body)

A macro similar to defn, that defines a new effect.

(defn-effect my-effect [arg]
  (change-the-world! args))

Calling it returns an effect action, which can be returned by an item as an action. The body of the effect then executed later, when side effects on some external entity are safe.

defn-item clj/s macro

(defn-item name params & body)

A macro like [[clojure.core/defn]] to define abstractions over items, with optional schema annotations similar to [[schema.core/defn]].

(defn-item col [w :- s/Int & content]
  (apply dom/div {:class (str "col-" w)} content))

The schema of the state that the returned item expects can also be specified like this:

(defn-item username :- s/Str []
  (with-state-as name
    (dom/div "Username:" name)))

Note that this does not specify the schema of the return value of the defined function, which is always an item.

Another alternative defines the returned items to be static, which means they do not depend on their state:

(defn-item menu-item :static [href]
  (dom/a {:href href}))

In all cases, the name of the var is attached to the returned items, which can be helpful in testing and debugging utilities (see named).

defn-subscription clj/s macro

(defn-subscription name deliver! args & body)

A macro to define the integration of an external source of actions, that needs an imperative way to 'inject' actions into an application. This could be an interval timer, for example:

(defn-subscription interval-timer deliver! [ms]
  (let [id (.setInterval js/window (fn [] (deliver! (js/Date.))) ms)]
    (fn []
      (.clearInterval js/window id))))

With this definition, you can use (interval-timer 1000) as an item in your application. That item will be invisible, but will emit a JavaScript Date object as an action every second.

Note that deliver! can be called directly in the body of defn-subscription to emit some actions immediately, or it can be called later from an asynchronous context. Also note that the body is evaluated as soon as the subscription item is mounted into your application, and that it must result in a function with no arguments, which is called when the item is removed from the application afterwards.

A schema annotation is possible after the name of the deliver function, to document and validate the action values emitted by the subscription item:

(defn-subscription window-width ^:always-validate deliver! :- s/Int []
  (let [id (.setInterval js/window (fn [] (deliver! js/window.innerWidth)) 100)]
    (fn []
      (.clearInterval js/window id))))

deref clj/s

(deref ref)

Returns a runner specific value, which might be a native dom element backing an item at runtime for example. See with-ref for a description of references.

dynamic clj/s

(dynamic f & args)

Returns a dynamic item, which looks and behaves like the item returned from (f state & args), which is evaluated each time the state changes.

effect clj/s

(effect f & args)

Returns an effect action, which, when run, calls the given function with the given arguments. The result of that function is ignored, unless you use execute-effect, or return a return value with new actions or messages.

empty clj/s

An invisible item with no behavior.

execute-effect clj/s

(execute-effect eff & [f])

Returns an item that executes the given effect once, optionally feeding its result into (f state result), which must return a return value.

Note that you can execute an effect also by using (return :action effect), if the result of the effect is irrelevant.

finalize clj/s

(finalize ret)

An invisible item that 'emits' the given return value once as a cleanup after the item was used somewhere in the component tree.

fmap-effect clj/s

(fmap-effect eff f & args)

Returns an effect like eff, whose result is f applied to the result of the given effect.

focus clj/s

(focus lens item)

Returns an item that focuses the outer state, to the part of it that item shall see, via the given lens. Otherwise behaves and looks the same.

forward-messages clj/s

(forward-messages f & args)

Returns an item like (f ref & args) where ref is a reference to which any messages sent to the returned item is forwarded to. You must use refer to define which item that is further down in the item.

fragment clj/s

(fragment & children)

Returns a container item consisting of the given child items.

handle-action clj/s

(handle-action item f)

Handles actions emitted by given item, by evaluating (f state action) for each of them. That must return the result of calling return with either a new state, and maybe one or more other actions (or the given action unchanged).

handle-effect-result clj/s deprecated

(handle-effect-result f eff)

handle-error clj/s

(handle-error item f)

Creates an error boundary around the given item. When the rendering of e throws an exception, then (f state error) is evaluated, and must result in an return value. Note that exceptions in functions like handle-action, are not catched by this. See try-catch for a higher level construct to handle errors.

handle-message clj/s

(handle-message f item)

Handles the messages sent to the the resulting item (either via reacl-c.main/send-message! or return), by calling (f state message), which must return a return value. The resulting item otherwise looks and behaves exactly like the given one.

handle-state-change clj/s

(handle-state-change item f)

Returns an item like the given item, but when a state change is emitted by item, then (f prev-state new-state) is evaluated, which must return a return value. By careful with this, as item usually expect that their changes to the state are eventually successful.

init clj/s

(init ret)

An invisible item that 'emits' the given return value once as an initialization.

isolate-state clj/s

(isolate-state initial-state item)

Hides the state of the given item as a local state, resulting in an item with an arbitrary state that is inaccessible for it.

item? clj/s

(item? v)

Returns true if is an item, and false otherwise.

keep-state clj/s

A unique value for the state in a return value, representing that the state should not be changed.

keyed clj/s

(keyed item key)

Adds an arbitrary identifier to the given item, which will be used to optimize rendering of it in a list of children of a container item.

lifecycle clj/s

(lifecycle init finish)

Returns an invisible item, that calls init each time the item is used at a place in the component hierarchy, including every change of state or the init function itself subsequently. The finish function is called when the item is no longer used at that place. Both functions must return a return value specifying what to do.

local-state clj/s

(local-state initial item)

Returns an item which looks like the given item, with state outer, where the given item must take a tuple state [outer inner], and initial is an intial value for the inner state, which can then be changed by the item independantly from the outer state.

map-actions clj/s

(map-actions item f)

Returns an item that emits actions (f action), for each action emitted by item, and otherwise looks an behaves exacly the same. If (f action) is nil, then the original action is kept, allowing for f to be a map of the actions to replace.

map-effects clj/s

(map-effects item f)

Returns an item that emits actions (f effect), for each effect actionemitted byitem, and otherwise looks an behaves exacly the same. If(f effect)is nil, then the original effect action is kept, allowing forf` to be a map of the effects to replace. This also works for composed effects with seq-effects or par-effects, such that the effects used in there are mapped too.

map-messages clj/s deprecated

(map-messages f item)

Returns an item like the given one, that transforms all messages sent to it though (f msg), before they are forwarded to item.

merge-returned clj/s

(merge-returned & rets)

Merges multiple return values into one. Actions and messages are concatenated. If more than one contains a new state, the right-most state value is used.

monitor-state clj/s

(monitor-state item f & args)

When e changes its state, (f old-state new-state & args) is evaluted for side effects. Note that this is only called when the item changes its state 'by itself', not if the state was changed somewhere upwards in the item tree an is only passed down to the resulting item.

name-id clj/s

(name-id s)

Generates a fresh unique value that can be used to generate named items via named. Note that calling this twice with the same name returns different values. Use defonce to stabilize an id for hot code reloads.

named clj/s

(named name-id item)

Returns an item that looks and works exactly like the given item, but with has a user defined name, that appears and can be used in testing and debugging utilities. Use name-id to generate a unique name object. See def-item and defn-item for more convenient ways to create named items.

no-effect clj/s

An effect action that does nothing and returns nil.

once clj/s

(once f & [cleanup-f])

Returns an item that evaluates (f state) and emits the return value that it must return initially. On subsequent state updates, f is called too, but the returned return value is only emitted if it different than last time. In other words, the same return value is emitted only once. The optional (cleanup-f state) is evaluated, when the item is removed from the item tree afterwards.

Note that if you return a modified state, you must be careful to not cause an endless loop of updates.

par-effects clj/s

(par-effects eff & effs)

Compose effects, which are run in 'parallel' (i.e. in no particular order), into one effect that results in a sequence of the results of the individual effects.

redirect-messages clj/s

(redirect-messages ref item)

Return an item like the given one, but that handles all messages sent to it by redirecting them to the item specified by the given reference.

ref-let clj/s macro

(ref-let bindings & body)

A macro that defines some names to refer to the given items, which allows the names to be used as message target in the body.

For example, to create an item that redirects messages to one of its children based on some criteria, you can write:

(ref-let [child-1 (my-item-1 ...)
          child-2 (my-item-2 ...)]
  (handle-message (fn [_ msg]
                     (if (is-for-child-1? msg)
                       (return :message [child-1 msg])
                       (return :message [child-2 msg])))
    (div child-1 child-2)))

ref-let* clj/s

(ref-let* items f & args)

Returns an item, that calls f with a list and the given arguments, where the list consists of the given items, but modified in a way that makes them usable as message targets.

refer clj/s

(refer item ref)

Returns an item identical to the given item, but with the given reference assigned. Note that the returned item cannot be used more than once. See with-ref for a description of references.

This should only be used for messaging, but prefer ref-let for that. To get access to native DOM elements, set the :ref attribute of items in the [[reacl-c/dom]] namespace.

return clj/s

(return :state state :action action :message [target message])

Creates a value to be used for example in the function passed to handle-action. All arguments are optional:

• :state means that the item changes its state to the given value
• :action means that the given action is emitted by the item
• :message means that the given message is sent to the given target (a reference or a item with a reference assigned).

If no :state option is used, the state of the item will not change. :state must occur at most once, :message and :action can be specified multiple times.

returned-actions clj/s

A lens over a list of the actions contained in a return value.

returned-messages clj/s

A lens over a list of the messages contained in a return value, as tuples [target message].

returned-state clj/s

A lens over the state contained in a return value. No state is represented by the unique value keep-state.

returned? clj/s

(returned? v)

Returns whether the given value is a return value.

seq-effects clj/s

(seq-effects eff & fs)

Sequentially compose two or more effects. The first argument must be an effect action, and the following must be functions that are called with the result of the previous one and must return a new effect action.

static clj/s

(static f & args)

Returns an item that is always like (f & args), independant of state changes. The item returned by f must not access state nor change it.

SubscribedMessage clj

subscription clj/s

(subscription f & args)

Returns an item that emits actions according to the given function f. Each time the retuned item is used, f will be called with a side-effectful deliver! function which takes the action to emit, and f must return a stop function of no arguments. You can call deliver! immediately once or multiple times, and you may also do some kind of registration at an asynchronous library or native browser api, and use deliver! to inform your application about the results later, once or multiple times. But when the stop function is called, you must prevent any more calls to deliver!.

try-catch clj/s

(try-catch try-item catch-item)

Returns an item that looks an works the same as the item try-item, until an error is thrown during its rendering. After that catch-item is rendered instead, with a state of the combined outer state and the error - [state-of-e error]. The catch-item will usually be interactive, for example, displaying the error (and the relevant part of the state) to the user, and offer a button to reset the error to nil and maybe fix the state, after which try-item is showed again.

validation-boundary clj/s

(validation-boundary item validate!)

Returns an item that forms a state validation boundary around the given item, where (validate! state :up) is evaluated for side effects when a state change is flowing out of then item upwards, and (validate! state :down) is evaluated for side effects when a new state is being pushed down.

with-bind clj/s

(with-bind f)

Returns an item that will call f with a bind function, which should return an item then. The bind function can then be used, to bind an event handler function to operate on the state of the returned item, even if it is used on a dom element with a different state, or it can also be triggered directly via call from a handler function with a different state.

Note: reacl-c.dom/defn-dom does this binding automatically, so you usually don't have to use this yourself.

with-message-target clj/s deprecated

(with-message-target handle-msg f & args)

Returns an item like ´(f target & args), wheretargetis a reference that can be used as a message target, which are then handled by a call to(handle-msg state msg)`, which must return a return value.

with-ref clj/s

(with-ref f & args)

Creates an item identical to the one returned from (f ref & args), where ref is a fresh reference. A reference should be assigned to one of the items below via refer. You can use it as the target of a (return :message [target msg]) for example.

with-refs clj/s

(with-refs n f & args)

Returns an item that calls f with a list of n references and any remaining args. See with-ref.

with-state-as clj/s macro

(with-state-as binding-form & body)

Returns an item that can look differently depending on its current state.

The basic form is

(with-state-as foo
  (dom/div (pr-str foo)))

where foo is bound to the current state of the returned item. The binding form can optionally be followed by a schema.core annotation:

(with-state-as foo :- s/Str
  (dom/div foo))

The binding form can also use destructuring

(with-state-as {name :name}
  (dom/div name))

If the binding form is a vector, the second part of the state can be declared to be local to the body item of the form:

(with-state-as [outer inner :local ""]
  (dom/div (str outer "->" inner)))

Note that the state of the inner item (the div in this case), will be a tuple (see local-state) of both outer and inner state, and that the state of the item created by with-state-as is just the first part of that tuple. The expression after :local is the initial value of the local state.