side-effectis a general term in computer science. In the context of an app, it means any interaction with the world outside of the internal logic of your app. Typical examples of a include API requests, analytics, logging, local storage, and so on.
aperturecontrols the streams of data which enter Refract.
type Aperture<P, E, C> = (
) => Observable<E>
It is a function which observes data sources within your app, passes this data through any necessary logic flows, and outputs a stream of
effectvalues in response.
effectis any value, passed from an
handler. These can be any value: numbers, strings, booleans, etc - you get to decide how to structure your effects.
It's expected that for most applications,
handlercauses side-effects in response to any
effectvalue output by the
type Handler<P, E> = (initialProps: P, initialContext: C) => (effect: E) => void
It is a function which imperatively calls any side-effect you wish to result from the output of your aperture. This often includes returning data to your app's flow (via
dispatchfor example), but could also include external side-effects which do not loop back into your app (such as localstorage or analytics).
errorHandlercauses side-effects in response to any fatal error occurring within your
type ErrorHandler<P> = (
) => (error: any) => void
It is a function which calls any side-effect you wish to result from any fatal errors within your streams. In some situations, an error can occur which breaks your stream pipeline. In this case, the error is handled by your
errorHandler. Usually, you would be expected to log this error for further investigation.