RealmDictionary - Java SDK
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New in version 10.6.0.
You can use the RealmDictionary data type to manage a collection of
unique String keys paired with values. RealmDictionary
implements Java's Map interface, so it works just like the built-in
HashMap class, except managed RealmDictionary instances persist
their contents to a realm. RealmDictionary instances that
contain Realm objects store references to those objects.
When you delete a Realm object from a realm, any
references to that object in a RealmDictionary become null
values.
Usage
To create a field of type RealmDictionary, define an object property
of type RealmDictionary<T>, where T defines the values you would
like to store in your RealmDictionary. Currently, RealmDictionary
instances can only use keys of type String.
The following table shows which methods you can use to complete common
collection tasks with RealmDictionary:
Task | Method |
|---|---|
Add an object to a RealmDictionary | put() (or the [] operator in Kotlin) |
Add multiple objects to a RealmDictionary | |
Check if the dictionary contains an specific key | |
Check if the dictionary contains a specific value |
Notifications
To subscribe to changes to a RealmDictionary, pass a
MapChangeListener
implementation to the RealmSet.addChangeListener method.
Your MapChangeListener implementation must define an
onChange() method, which accepts a reference to the changed RealmDictionary
and a set of changes as parameters. You can access the keys
added to the dictionary as well as the keys removed from the dictionary
through the MapChangeSet parameter.