5643f8f6d2
* Added docs with new screenshots * Added doc to architecture * Added documentations to various extension modules * Added more documentation to modes * Added docs to managers * Added docs for services * Fixed deployment docs * Added white labelling documentation * Added i18n docs and measurement export
111 lines
3.2 KiB
Markdown
111 lines
3.2 KiB
Markdown
# Pub sub
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## Overview
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Publish–subscribe pattern is a messaging pattern that is one of the fundamentals patterns used in reusable software components.
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In short, services that implements this pattern, can have listeners subscribed to their broadcasted events. After the event is fired, the corresponding listener will execute the function that is registered.
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You can read more about this design pattern [here](https://cloud.google.com/pubsub/docs/overview).
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## Example: Default Initialization
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In `Mode.jsx` we have a default initialization that demonstrates
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a series of subscriptions to various events.
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```js
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async function defaultRouteInit({
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servicesManager,
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studyInstanceUIDs,
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dataSource,
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}) {
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const {
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DisplaySetService,
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HangingProtocolService,
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} = servicesManager.services;
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const unsubscriptions = [];
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const {
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unsubscribe: instanceAddedUnsubscribe,
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} = DicomMetadataStore.subscribe(
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DicomMetadataStore.EVENTS.INSTANCES_ADDED,
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({ StudyInstanceUID, SeriesInstanceUID, madeInClient = false }) => {
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const seriesMetadata = DicomMetadataStore.getSeries(
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StudyInstanceUID,
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SeriesInstanceUID
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);
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DisplaySetService.makeDisplaySets(seriesMetadata.instances, madeInClient);
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}
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);
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unsubscriptions.push(instanceAddedUnsubscribe);
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studyInstanceUIDs.forEach(StudyInstanceUID => {
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dataSource.retrieveSeriesMetadata({ StudyInstanceUID });
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});
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const { unsubscribe: seriesAddedUnsubscribe } = DicomMetadataStore.subscribe(
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DicomMetadataStore.EVENTS.SERIES_ADDED,
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({ StudyInstanceUID }) => {
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const studyMetadata = DicomMetadataStore.getStudy(StudyInstanceUID);
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HangingProtocolService.run(studyMetadata);
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}
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);
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unsubscriptions.push(seriesAddedUnsubscribe);
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return unsubscriptions;
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}
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```
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## Unsubscription
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You need to be careful if you are adding custom subscriptions to the app. Each subscription will return a unsubscription function that needs to be executed on component destruction to avoid adding multiple subscriptions to the same observer.
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Below, we can see `simplified` `Mode.jsx` and the corresponding `useEffect` where the unsubscription functions are executed upon destruction.
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```js
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// platform/viewer/src/routes/Mode/Mode.jsx
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export default function ModeRoute(/**..**/) {
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/**...**/
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useEffect(
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() => {
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/**...**/
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DisplaySetService.init(extensionManager, sopClassHandlers)
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extensionManager.onModeEnter()
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mode?.onModeEnter({ servicesManager, extensionManager })
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hangingProtocols.forEach((extentionProtocols) => {
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const { protocols } =
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extensionManager.getModuleEntry(extentionProtocols)
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HangingProtocolService.addProtocols(protocols)
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})
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const setupRouteInit = async () => {
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if (route.init) {
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return await route.init(/**...**/)
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}
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return await defaultRouteInit(/**...**/)
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}
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let unsubscriptions
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setupRouteInit().then((unsubs) => {
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unsubscriptions = unsubs
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})
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return () => {
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extensionManager.onModeExit()
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mode?.onModeExit({ servicesManager, extensionManager })
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unsubscriptions.forEach((unsub) => {
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unsub()
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})
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}
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},
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)
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return <> /**...**/ </>
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}
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```
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