R: Add callbacks for Shiny session events

onFlush {shiny} | R Documentation

## Add callbacks for Shiny session events

### Description

These functions are for registering callbacks on Shiny session events. `onFlush` registers a function that will be called before Shiny flushes the reactive system. `onFlushed` registers a function that will be called after Shiny flushes the reactive system. `onSessionEnded` registers a function to be called after the client has disconnected.

### Usage

    onFlush(fun, once = TRUE, session = getDefaultReactiveDomain())

    onFlushed(fun, once = TRUE, session = getDefaultReactiveDomain())

    onSessionEnded(fun, session = getDefaultReactiveDomain())

### Arguments

`fun` | A callback function.
`once` | Should the function be run once, and then cleared, or should it re-run each time the event occurs. (Only for `onFlush` and `onFlushed`.)
`session` | A shiny session object.

### Details

These functions should be called within the application's server function.

All of these functions return a function which can be called with no arguments to cancel the registration.

### See Also

`onStop()` for registering callbacks that will be invoked when the application exits, or when a session ends.

[Package shiny version 1.2.0 Index]