re-frame.core-instrumented¶

A mirror of re-frame.core.

This namespace exposes every public symbol from core with the same call shape, so adopting it is just an alias swap:

;; before
(:require [re-frame.core              :as rf])

;; after — same calls, same code
(:require [re-frame.core-instrumented :as rf])

What changes: the entry points you reach for most often (dispatch, subscribe, reg-event-db, …) are wrapped so that tooling like re-frame-10x and re-frame-pair can show you which file and line each call came from.

See re-frame.core for the documentation of each symbol — this namespace mirrors its contract.

Dispatching Events¶

dispatch¶

(dispatch event-v)

Like re-frame.core/dispatch but in DEBUG builds attaches {:file :line} on the event vector as :re-frame/source metadata. Production CLJS builds (goog.DEBUG=false) emit a bare re-frame.core/dispatch call after Closure DCE — no if, no vary-meta, no allocation.

Read inside handlers via (:re-frame/source (meta event)) or via the existing trace's :event tag.

The macro uses standard vary-meta so any user-supplied event metadata survives the merge.

dispatch-sync¶

(dispatch-sync event-v)

Like re-frame.core/dispatch-sync but attaches call-site source meta in DEBUG builds. See dispatch for the rationale and DCE behaviour.

dispatch-with¶

(dispatch-with event-v overrides)

Like re-frame.core/dispatch-with but attaches call-site source meta on the event vector in DEBUG builds. See dispatch for the rationale and DCE behaviour. overrides is passed through unchanged.

dispatch-sync-with¶

(dispatch-sync-with event-v overrides)

Like re-frame.core/dispatch-sync-with but attaches call-site source meta on the event vector in DEBUG builds. See dispatch for the rationale and DCE behaviour. overrides is passed through unchanged.

dispatch-and-settle¶

(dispatch-and-settle event-v)

(dispatch-and-settle event-v opts)

Like re-frame.core/dispatch-and-settle but attaches call-site source meta on the event vector in DEBUG builds. See dispatch for the rationale and DCE behaviour. opts is passed through unchanged.

Subscriptions¶

(subscribe query-v)

(subscribe query-v dynv)

Like re-frame.core/subscribe but in DEBUG builds attaches {:file :line} on the query vector as :re-frame/source metadata before lookup. Production CLJS builds (goog.DEBUG=false) emit a bare re-frame.core/subscribe call after Closure DCE.

Cache identity is unaffected: vector and map equality in CLJ/CLJS ignore metadata, and re-frame.subs/cache-key keys on plain = so ^{:re-frame/source ...} [:foo] and bare [:foo] resolve to the same cached reaction.

Recover the meta'd query-v via re-frame.subs/query-v-for-reaction on the returned reaction, or read the :input-query-vs tag on :sub/run traces.

Supports the same arities as re-frame.core/subscribe, including the historical [query-v dynv] form. Source metadata is attached to query-v; dynv is passed through unchanged.

reg-sub¶

(reg-sub query-id & args)

Like re-frame.core/reg-sub but in DEBUG builds attaches {:file :line} as metadata on the registered subscription handler so (meta (re-frame.registrar/get-handler :sub query-id)) returns the call-site location. Production CLJS builds emit a bare re-frame.core/reg-sub call after Closure DCE.

Variadic — supports the same :<- / :-> / :=> sugar pairs as re-frame.core/reg-sub. Macro, so (apply reg-sub ...) won't compile; use re-frame.core/reg-sub for that.

reg-sub-raw¶

(reg-sub-raw query-id handler-fn)

Like re-frame.core/reg-sub-raw but in DEBUG builds attaches {:file :line} as metadata on the registered subscription handler. Source-meta is decorated under the same :sub kind as reg-sub, so existing tooling reads it the same way.

clear-sub¶

(clear-sub)

(clear-sub query-id)

Unregisters subscription handlers (presumably registered previously via the use of reg-sub).

When called with no args, it will unregister all currently registered subscription handlers.

When given one arg, assumed to be the id of a previously registered subscription handler, it will unregister the associated handler. Will produce a warning to console if it finds no matching registration.

NOTE: Depending on the usecase, it may be necessary to call clear-subscription-cache! afterwards

clear-subscription-cache!¶

(clear-subscription-cache!)

Removes all subscriptions from the cache.

This function can be used at development time or test time. Useful when hot reloading namespaces containing subscription handlers. Also call it after a React/render exception, because React components won't have been cleaned up properly. And this, in turn, means the subscriptions within those components won't have been cleaned up correctly. So this forces the issue.

query-v-for-reaction¶

(query-v-for-reaction reaction)

Returns the query-v that produced reaction, or nil if the reaction is unknown to re-frame's subscription cache.

The inverse of subscribe: given a reaction held by tooling or a diagnostic recipe, recover the query-v that originally produced it. Backed by an object-identity-keyed reverse map maintained alongside the subscription cache; entries are cleared when the reaction is disposed.

live-query-vs¶

(live-query-vs)

Returns a sequence of all currently-live query-vectors — one entry per active cached subscription.

A snapshot of the subscription cache at call time; does not update reactively. Useful for devtools and diagnostic tools that need to enumerate active subscriptions without relying on internal cache structure details.

Event Handlers¶

reg-event-db¶

(reg-event-db id handler)

(reg-event-db id interceptors handler)

Like re-frame.core/reg-event-db but in DEBUG builds attaches {:file :line} as metadata on the registered interceptor chain so (meta (re-frame.registrar/get-handler :event id)) returns the call-site location. Production CLJS builds (goog.DEBUG=false) emit a bare re-frame.core/reg-event-db call after Closure DCE.

Macro — cannot be used in value position. For (map reg-event-db ...) or (apply reg-event-db ...) use re-frame.core/reg-event-db instead.

reg-event-fx¶

(reg-event-fx id handler)

(reg-event-fx id interceptors handler)

Like re-frame.core/reg-event-fx but attaches call-site source meta on the registered interceptor chain in DEBUG builds. See reg-event-db for the rationale and DCE behaviour.

reg-event-ctx¶

(reg-event-ctx id handler)

(reg-event-ctx id interceptors handler)

Like re-frame.core/reg-event-ctx but attaches call-site source meta on the registered interceptor chain in DEBUG builds. See reg-event-db for the rationale and DCE behaviour.

reg-event-error-handler¶

(reg-event-error-handler handler)

Like re-frame.core/reg-event-error-handler but in DEBUG builds attaches {:file :line} as metadata on the registered handler so (meta (re-frame.registrar/get-handler :error :event-handler)) returns the call-site location. Production CLJS builds emit a bare re-frame.core/reg-event-error-handler call after Closure DCE.

The error handler is registered under the fixed registrar entry [:error :event-handler] (only one error handler is supported re-frame-wide); the macro mirrors that contract.

clear-event¶

(clear-event)

(clear-event id)

Unregisters event handlers (presumably registered previously via the use of reg-event-db or reg-event-fx).

When called with no args, it will unregister all currently registered event handlers.

When given one arg, assumed to be the id of a previously registered event handler, it will unregister the associated handler. Will produce a warning to console if it finds no matching registration.

Effect Handlers¶

reg-fx¶

(reg-fx id handler)

Like re-frame.core/reg-fx but in DEBUG builds attaches {:file :line} as metadata on the registered effect handler so (meta (re-frame.registrar/get-handler :fx id)) returns the call-site location. Production CLJS builds emit a bare re-frame.core/reg-fx call after Closure DCE.

clear-fx¶

(clear-fx)

(clear-fx id)

Unregisters effect handlers (presumably registered previously via the use of reg-fx).

When called with no args, it will unregister all currently registered effect handlers.

When given one arg, assumed to be the id of a previously registered effect handler, it will unregister the associated handler. Will produce a warning to console if it finds no matching registration.

Coeffects¶

reg-cofx¶

(reg-cofx id handler)

Like re-frame.core/reg-cofx but in DEBUG builds attaches {:file :line} as metadata on the registered coeffect handler so (meta (re-frame.registrar/get-handler :cofx id)) returns the call-site location. Production CLJS builds emit a bare re-frame.core/reg-cofx call after Closure DCE.

clear-cofx¶

(clear-cofx)

(clear-cofx id)

Unregisters coeffect handlers (presumably registered previously via the use of reg-cofx).

When called with no args, it will unregister all currently registered coeffect handlers.

When given one arg, assumed to be the id of a previously registered coeffect handler, it will unregister the associated handler. Will produce a warning to console if it finds no matching registration.

inject-cofx¶

(inject-cofx id)

(inject-cofx id value)

Given an id, and an optional, arbitrary value, returns an interceptor whose :before adds to the :coeffects (map) by calling a pre-registered 'coeffect handler' identified by the id.

The previous association of a coeffect handler with an id will have happened via a call to re-frame.core/reg-cofx - generally on program startup.

Within the created interceptor, this 'looked up' coeffect handler will be called (within the :before) with two arguments:

the current value of :coeffects
optionally, the originally supplied arbitrary value

This coeffect handler is expected to modify and return its first, coeffects argument.

Example of inject-cofx and reg-cofx working together

First - Early in app startup, you register a coeffect handler for :datetime:

(re-frame.core/reg-cofx
  :datetime                        ;; usage  (inject-cofx :datetime)
  (fn coeffect-handler
    [coeffect]
    (assoc coeffect :now (js/Date.))))   ;; modify and return first arg

Second - Later, add an interceptor to an -fx event handler, using inject-cofx:

(re-frame.core/reg-event-fx            ;; when registering an event handler
  :event-id
  [ ... (inject-cofx :datetime) ... ]  ;; <-- create an injecting interceptor
  (fn event-handler
    [coeffect event]
      ;;... in here can access (:now coeffect) to obtain current datetime ...
    )))

Background

coeffects are the input resources required by an event handler to perform its job. The two most obvious ones are db and event. But sometimes an event handler might need other resources.

Perhaps an event handler needs a random number or a GUID or the current datetime. Perhaps it needs access to a DataScript database connection.

If an event handler directly accesses these resources, it stops being pure and, consequently, it becomes harder to test, etc. So we don't want that.

Instead, the interceptor created by this function is a way to 'inject' 'necessary resources' into the :coeffects (map) subsequently given to the event handler at call time.

Miscellaneous¶

add-post-event-callback¶

(add-post-event-callback f)

(add-post-event-callback id f)

Registers the given function f to be called after each event is processed.

f will be called with two arguments:

event: a vector. The event just processed.
queue: a PersistentQueue, possibly empty, of events yet to be processed.

This facility is useful in advanced cases like:

you are implementing a complex bootstrap pipeline
you want to create your own handling infrastructure, with perhaps multiple handlers for the one event, etc. Hook in here.
libraries providing 'isomorphic javascript' rendering on Nodejs or Nashorn.

id is typically a keyword. If it supplied when an f is added, it can be subsequently be used to identify it for removal. See remove-post-event-callback.

remove-post-event-callback¶

(remove-post-event-callback id)

Unregisters a post event callback function, identified by id.

Such a function must have been previously registered via add-post-event-callback

make-restore-fn¶

(make-restore-fn)

This is a utility function, typically used in testing.

It checkpoints the current state of re-frame and returns a function which, when later called, will restore re-frame to the checkpointed state.

The checkpoint includes app-db, all registered handlers and all subscriptions.

purge-event-queue¶

(purge-event-queue)

Removes all events currently queued for processing

version¶

Runtime-readable string identifying the deployed re-frame artifact — useful for devtools, instrumentation, and version-floor probes that need to know which re-frame they're running against without parsing pom.xml.

Re-exported from re-frame.config/version; see that namespace for the build-time override hook (:closure-defines in shadow-cljs).

Writing Interceptors¶

enqueue¶

(enqueue context interceptors)

A utility function, used when writing an interceptor's :before function.

Adds the given collection of interceptors to those already in context's execution :queue. It returns the updated context.

So, it provides a way for one interceptor to add more interceptors to the currently executing interceptor chain.

get-coeffect¶

(get-coeffect context)

(get-coeffect context key)

(get-coeffect context key not-found)

A utility function, typically used when writing an interceptor's :before function.

When called with one argument, it returns the :coeffects map from within that context.

When called with two or three arguments, behaves like clojure.core/get and returns the value mapped to key in the :coeffects map within context, not-found or nil if key is not present.

assoc-coeffect¶

(assoc-coeffect context key value)

A utility function, typically used when writing an interceptor's :before function.

Adds or updates a key/value pair in the :coeffects map within context.

get-effect¶

(get-effect context)

(get-effect context key)

(get-effect context key not-found)

A utility function, used when writing interceptors, typically within an :after function.

When called with one argument, returns the :effects map from the context.

When called with two or three arguments, behaves like clojure.core/get and returns the value mapped to key in the effects map, not-found or nil if key is not present.

assoc-effect¶

(assoc-effect context key value)

A utility function, typically used when writing an interceptor's :after function.

Adds or updates a key/value pair in the :effects map within context.

->interceptor¶

(->interceptor & {:as m, :keys [id before after]})

A utility function for creating interceptors.

Accepts three optional, named arguments:

:id - an id for the interceptor (decorative only)
:before - the interceptor's before function
:after - the interceptor's after function

Example use:

(def my-interceptor
  (->interceptor
   :id     :my-interceptor
   :before (fn [context]
             ... modifies and returns `context`)
   :after  (fn [context]
             ... modifies and returns `context`)))

Notes:

:before functions modify and return their context argument. Sometimes they only side effect, in which case, they'll perform the side effect and return context unchanged.
:before functions often modify the :coeffects map within context and, if they do, then they should use the utility functions get-coeffect and assoc-coeffect.
:after functions modify and return their context argument. Sometimes they only side effect, in which case, they'll perform the side effect and return context unchanged.
:after functions often modify the :effects map within context and, if they do, then they should use the utility functions get-effect and assoc-effect

Global Interceptors¶

clear-global-interceptor¶

(clear-global-interceptor)

(clear-global-interceptor id)

Unregisters global interceptors (presumably registered previously via the use of reg-global-interceptor).

When called with no args, it will unregister all currently registered global interceptors.

When given one arg, assumed to be the id of a previously registered global interceptors, it will unregister the associated interceptor. Will produce a warning to console if it finds no matching registration.

reg-global-interceptor¶

(reg-global-interceptor interceptor)

Registers the given interceptor as a global interceptor. Global interceptors are included in the processing chain of every event.

When you register an event handler, you have the option of supplying an interceptor chain. Any global interceptors you register are effectively prepending to this chain.

Global interceptors are run in the order that they are registered.

Global interceptors are unique by :id. If a global interceptor with the same :id key as interceptor is already registered, interceptor will take its place in the global interceptor chain. This facilitates hot-reloading.

Note: members of re-frame.std-interceptors do not have unique ids. To register more than one, consider:

(reg-global-interceptor (-> (re-frame.std-interceptors/on-changes + [:a] [:b]) (assoc :id :my-unique-id)))

Interceptors¶

path¶

(path & args)

Returns an interceptor which acts somewhat like clojure.core/update-in, in the sense that the event handler is given a specific part of app-db to change, not all of app-db.

The interceptor has both a :before and :after functions. The :before replaces the :db key within coeffects with a sub-path within app-db. The :after reverses the process, and it grafts the handler's return value back into db, at the right path.

Examples:

(path :some :path)
(path [:some :path])
(path [:some :path] :to :here)
(path [:some :path] [:to] :here)

Example Use:

(reg-event-db
  :event-id
  (path [:a :b])  ;; <-- used here, in interceptor chain
  (fn [b v]       ;; 1st arg is not db. Is the value from path [:a :b] within db
    ... new-b))   ;; returns a new value for that path (not the entire db)

Notes:

path may appear more than once in an interceptor chain. Progressive narrowing.
if :effects contains no :db effect, can't graft a value back in.

enrich¶

(enrich f)

Returns an interceptor which will run the given function f in the :after position.

f is called with two arguments: db and event, and is expected to return a modified db.

Unlike the after interceptor which is only about side effects, enrich expects f to process and alter the given db coeffect in some useful way, contributing to the derived data, flowing vibe.

If f returns nil, the db value passed to f will be returned instead.

Example Use:¶

Imagine that todomvc needed to do duplicate detection - if any two todos had the same text, then highlight their background, and report them via a warning at the bottom of the panel.

Almost any user action (edit text, add new todo, remove a todo) requires a complete reassessment of duplication errors and warnings. E.g. that edit just made might have introduced a new duplicate, or removed one. Same with any todo removal. So we need to re-calculate warnings after any CRUD events associated with the todos list.

Unless we are careful, we might end up coding subtly different checks for each kind of CRUD operation. The duplicates check made after 'delete todo' event might be subtly different to that done after an editing operation. Nice and efficient, but fiddly. A bug generator approach.

So, instead, we create an f which recalculates ALL warnings from scratch every time there is ANY change. It will inspect all the todos, and reset ALL FLAGS every time (overwriting what was there previously) and fully recalculate the list of duplicates (displayed at the bottom?).

https://twitter.com/nathanmarz/status/879722740776939520

By applying f in an :enrich interceptor, after every CRUD event, we keep the handlers simple and yet we ensure this important step (of getting warnings right) is not missed on any change.

We can test f easily - it is a pure function - independently of any CRUD operation.

This brings huge simplicity at the expense of some re-computation each time. This may be a very satisfactory trade-off in many cases.

Returning nil¶

In some cases, it's useful to apply a change to specific situations that can be determined at runtime instead of when defining the handler with an :enrich interceptor. Instead of forcing you to return the db from every non-applicable branch, you can return nil to use the given db value:

(def set-last-update
  (core/enrich
    (fn [{db :db} [_ {user :user}]]
      (when (active-user? user)  ;; <- Only perform an update if user is active
        ...))))

after¶

(after f)

Returns an interceptor which runs the given function f in the :after position, presumably for side effects.

f is called with two arguments: the :effects value for :db (or the :coeffect value of :db if no :db effect is returned) and the event. Its return value is ignored, so f can only side-effect.

An example of use can be seen in the re-frame github repo in /examples/todomvc/events.cljs:

f runs schema validation (reporting any errors found).
f writes to localstorage.

on-changes¶

(on-changes f out-path & in-paths)

Returns an interceptor which will observe N paths within db, and if any of them test not identical? to their previous value (as a result of a event handler being run), then it will run f to compute a new value, which is then assoc-ed into the given out-path within db.

Example Usage:

(defn my-f
  [a-val b-val]
  ... some computation on a and b in here)

;; use it
(def my-interceptor (on-changes my-f [:c] [:a] [:b]))

(reg-event-db
  :event-id
  [... my-interceptor ...]  ;; <-- ultimately used here
  (fn [db v]
     ...))

If you put this interceptor on handlers which might change paths :a or :b, it will:

call f each time the value at path [:a] or [:b] changes
call f with the values extracted from [:a] [:b]
assoc the return value from f into the path [:c]

debug¶

An interceptor which logs/instruments an event handler's actions to re-frame/console at the :log level.

Output includes:

the event vector
a clojure.data/diff of db, before vs after, which shows the changes caused by the event handler. To understand the output, you should understand: https://clojuredocs.org/clojure.data/diff.

You'd typically include this interceptor after (to the right of) any path interceptor.

Warning: calling clojure.data/diff on large, complex data structures can be slow. So, you won't want this interceptor present in production code. So, you should condition it out like this:

(re-frame.core/reg-event-db
  :evt-id
  [(when ^boolean goog.DEBUG re-frame.core/debug)]  ;; <-- conditional
  (fn [db v]
     ...))

To make this code fragment work, you'll also have to set goog.DEBUG to false in your production builds. For an example, look in project.clj of /examples/todomvc.

unwrap¶

New in v1.2.0

An interceptor which decreases the amount of destructuring necessary in an event handler where the event is structured as a 2-vector of [event-id payload-map].

It promotes the payload-map part to be the event ultimately given to the event handler. Should you want the full original event, it can be found in coeffects under the key :original-event.

If a dispatch looked like this:

 (dispatch [:event-id {:x 1 :y 2 :z 3}])

Your event handlers can look like this:

 (reg-event-fx
   :event-id
   [... unwrap ...]                    ;; <-- added to the interceptors
   (fn [{:keys [db]} {:keys [x y z]}]  ;; <-- instead of [_ {:keys [x y z]}]
     ...)

trim-v¶

An interceptor which removes the first element of the event vector, before it is supplied to the event handler, allowing you to write more aesthetically pleasing event handlers. No leading underscore on the event-v!

Should you want the full original event, it can be found in coeffects under the key :original-event.

Your event handlers will look like this:

(reg-event-db
  :event-id
  [... trim-v ...]    ;; <-- added to the interceptors
  (fn [db [x y z]]    ;; <-- instead of [_ x y z]
    ...)

Logging¶

set-loggers!¶

(set-loggers! new-loggers)

re-frame outputs warnings and errors via the API function console which, by default, delegates to js/console's default implementation for log, error, warn, debug, group and groupEnd. But, using this function, you can override that behaviour with your own functions.

The argument new-loggers should be a map containing a subset of they keys for the standard loggers, namely :log :error :warn :debug :group or :groupEnd.

Example Usage:

(defn my-logger      ;; my alternative logging function
  [& args]
  (post-it-somewhere (apply str args)))

;; now install my alternative loggers
(re-frame.core/set-loggers!  {:warn my-logger :log my-logger})

console¶

(console level & args)

A utility logging function which is used internally within re-frame to produce warnings and other output. It can also be used by libraries which extend re-frame, such as effect handlers.

By default, it will output the given args to js/console at the given log level. However, an application using re-frame can redirect console output via set-loggers!.

level can be one of :log, :error, :warn, :debug, :group or :groupEnd.

Example usage:

(console :error "Sure enough it happened:" a-var "and" another)
(console :warn "Possible breach of containment wall at:" dt)

Tracing¶

tag-schema¶

Schema for :tags of every op-type re-frame emits.

validate-trace?¶

True iff runtime trace-tag validation is enabled.

set-validate-trace!¶

Enable or disable runtime trace-tag validation.

register-trace-cb¶

Register a callback that receives each batch of finished traces.

remove-trace-cb¶

Remove a trace callback by key.

register-epoch-cb¶

Register a callback that receives assembled epoch records.

remove-epoch-cb¶

Remove an epoch callback by key.

assemble-epochs¶

Partition a finished trace batch into event epoch records.

Deprecated¶

register-handler¶

(register-handler & args)

Deprecated. Use reg-event-db instead.

register-sub¶

(register-sub & args)

Deprecated. Use reg-sub-raw instead.

re-frame.core-instrumented¶

Dispatching Events¶

dispatch¶

dispatch-sync¶

dispatch-with¶

dispatch-sync-with¶

dispatch-and-settle¶

Subscriptions¶

subscribe¶

reg-sub¶

reg-sub-raw¶

clear-sub¶

clear-subscription-cache!¶

query-v-for-reaction¶

live-query-vs¶

Event Handlers¶

reg-event-db¶

reg-event-fx¶

reg-event-ctx¶

reg-event-error-handler¶

clear-event¶

Effect Handlers¶

reg-fx¶

clear-fx¶

Coeffects¶

reg-cofx¶

clear-cofx¶

inject-cofx¶

Miscellaneous¶

add-post-event-callback¶

remove-post-event-callback¶

make-restore-fn¶

purge-event-queue¶

version¶

Writing Interceptors¶

enqueue¶

get-coeffect¶

assoc-coeffect¶

get-effect¶

assoc-effect¶

->interceptor¶

Global Interceptors¶

clear-global-interceptor¶

reg-global-interceptor¶

Interceptors¶

path¶

enrich¶

Example Use:¶

Returning nil¶

after¶

on-changes¶

debug¶

unwrap¶

trim-v¶

Logging¶

set-loggers!¶

console¶

Tracing¶

tag-schema¶

validate-trace?¶

set-validate-trace!¶

register-trace-cb¶

remove-trace-cb¶

register-epoch-cb¶

remove-epoch-cb¶

assemble-epochs¶

Deprecated¶

register-handler¶

register-sub¶