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https://github.com/day8/re-frame-forward-events-fx
A re-frame effects handler for listening-for and then post-processing dispatched events
https://github.com/day8/re-frame-forward-events-fx
re-frame
Last synced: 2 months ago
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A re-frame effects handler for listening-for and then post-processing dispatched events
- Host: GitHub
- URL: https://github.com/day8/re-frame-forward-events-fx
- Owner: day8
- License: mit
- Created: 2016-07-15T12:42:18.000Z (over 8 years ago)
- Default Branch: master
- Last Pushed: 2021-11-04T22:53:54.000Z (about 3 years ago)
- Last Synced: 2024-10-28T13:41:52.388Z (3 months ago)
- Topics: re-frame
- Language: Clojure
- Homepage:
- Size: 174 KB
- Stars: 34
- Watchers: 11
- Forks: 4
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
- Contributing: CONTRIBUTING.md
- Funding: .github/FUNDING.yml
- License: LICENSE
Awesome Lists containing this project
README
[](https://clojars.org/day8.re-frame/forward-events-fx)
[](https://github.com/day8/re-frame-forward-events-fx/issues)
[](license.txt)
# re-frame-forward-events-fx
This re-frame library contains an [Effect Handler](https://github.com/day8/re-frame/tree/develop/docs),
keyed `:forward-events`, which allows you to listen-for, and then post-process events, typically for higher-level
control flow purposes (eg. coordination).
## Quick Start Guide
### Step 1. Add Dependency
Add the following project dependency:
[](https://clojars.org/day8.re-frame/forward-events-fx)
Also requires re-frame >= v0.8.0
### Step 2. Registration And Use
In the namespace where you register your event handlers, perhaps called `events.cljs`, you have 2 things to do.
**First**, add this require to the `ns`:
```clj
(ns app.events
(:require
...
[day8.re-frame.forward-events-fx] ;; <-- add this
...))
```
Because we never subsequently use this require, it
appears redundant. But its existence will cause the `:forward-events` effect
handler to self-register with re-frame, which is important
to everything that follows.
**Second**, use it when writing an effectful event handler:
```clj
(reg-event-fx ;; note the -fx
:my-event
(fn [world event] ;; note: world
{:db (assoc (:db world) :some :thing) ;; optional update to db
:forward-events {:register :coordinator1 ;; <-- used
:events #{:event1 :event2}
:dispatch-to [:coordinator 1]}}))
```
Notice the use of an effect `:forward-event`. This library defines the "effect handler" which implements `:forward-events`.
## Tutorial
This effect handler provides a way to "forward" events. To put it another way,
it provides a way to listen-for and then post-process events. Some might say it allows you to "sniff" certain events.
Normally, when `(dispatch [:a 42])` happens, the event will be routed to
the registered handler for `:a`, and that's the end of the matter.
But, with this effect, you can specify that a particular set of events be
forwarded to another handler for further processing __after__ normal handling.
This 2nd handler can then further process the events, often carrying out
some sort of meta level, coordination function.
The "forwarding" is done via a 2nd dispatch. The payload of this `dispatch`
is the __entire__ event dispatched in the first place.
`:forward-events` accepts the following keys (all mandatory):
- `:register` - an id, typically a keyword. Used when you later want to unregister a forwarder. Should be unique across all `:forward-event` effects.
- `:events` - the set of events for which you'd like to "listen"
- `:dispatch-to` a vector which represents the template for the "further event" to dispatch. The
detected event is provided (conj-ed) to this event template.
For clarity, here's a worked example. If you registered a ":forward-events" for event `:a` and you gave a `:dispatch-to` of `[:later :blah]`, then:
- when if any `(dispatch [:a 42])` happened,
- the handler for `:a` would be run normally. No change so far.
- but then a further dispatch would be happen: `(dispatch [:later :blah [:a 42]])`. The entire first event `[:a 42]` is "forwarded" in the further `dispatch`.
Examples of use:
```clj
{:forward-events {:register :an-id-for-this-listener
:events #{:event1 :event2}
:dispatch-to [:later "blah"]} ;; the forwarded event is conj to the end of this event vec
```
```clj
{:forward-events {:unregister :the-id-supplied-when-registering}}
```
When necessary, the value of `:forward-events` can also be a `list` of `maps`,
with each map either registering or unregistering.
## Testing
To run the tests in a browser
```
lein dev
```
To run the tests with Karma (i.e. for continuous integration)
```
sudo npm -g install karma-cli
lein ci
```