Reacting to Data Changes

You can react to changes in your local store by setting up a store observer. You can read more about store observers in Accessing Data.

Store observers are useful when you want to monitor changes from your local Ditto store and react to them immediately. For instance, when your end user updates their profile, asynchronously display changes in realtime.

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Setting Up Store Observers

Using the registerObserver method, set up an observer within the store namespace enclosed with a query that specifies the collection to watch for changes, as well as your logic to handle the incoming changes.

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Store Observer with Query Arguments

To associate arguments with your query add them as a parameter.

let observer = ditto.store.registerObserver(
  query: "SELECT * FROM cars WHERE color = :color",
  argumets: [ "color": "blue" ]){ result in /* handle change */ };

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Canceling a Store Observer

To cancel a store observer, call cancel on the observer object.

Once canceled, the store observer will stop processing in the background and will no longer call the provided callback.

observer.cancel()

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Accessing Store Observers

To access store observers from the local Ditto store:

ditto.store.observers