ohif-viewer/docs/latest/extensions/lifecycle/pre-registration.md
2019-12-08 14:37:42 -05:00

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# Lifecylce Hook: preRegistration
If an extension defines the `preRegistration` lifecycle hook, it is called
before any modules are registered in the `ExtensionManager`. This hook can be
used to:
- initialize 3rd party libraries
- register event listeners
- add or call services
- add or call commands
The `preRegistration` hook receives an object containing the
`ExtensionManager`'s associated `ServicesManager`, `CommandsManager`, and any
`configuration` that was provided with the extension at time of registration.
_Example `preRegistration` hook implementation_
```js
export default {
id: 'MyExampleExtension',
/**
* @param {ServicesManager} servicesManager
* @param {CommandsManager} commandsManager
* @param {object} configuration
* @returns void
*/
preRegistration({ servicesManager, commandsManager, configuration }) {
console.log('Wiring up important stuff.');
window.importantStuff = () => {
console.log(configuration);
};
console.log('Important stuff has been wired.');
window.importantStuff();
},
};
```