New Realm Data Types: Dictionaries/Maps, Sets, Mixed, and UUIDs
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Starting with Realm Javascript 10.5, Realm Cocoa 10.8, Realm .NET 10.2,
and Realm Java 10.6, developers will be able persist and query new
language specific data types in the Realm Database. These include
Dictionaries/Maps, Sets, a Mixed type, and UUIDs.
We're excited to announce that the Realm SDK team has shipped four new
data types for the Realm Mobile Database. This work – prioritized in
response to community requests – continues to make using the Realm SDKs
an intuitive, idiomatic experience for developers. It eliminates even
more boilerplate code from your codebase, and brings the data layer
closer to your app's source code.
These new types make it simple to model flexible data in
Realm, and easier to work across Realm and
MongoDB Atlas. Mobile developers
who are building with Realm and MongoDB Realm
Sync can leverage the
flexibility of MongoDB's data structure in their offline-first mobile
applications.
Read on to learn more about each of the four new data types we've
released, and see examples of when and how to use them in your data
modeling:
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Dictionaries/maps allow developers to store data in arbitrary key-value
pairs. They're used when a developer wants to add flexibility to data
models that may evolve over time, or handle unstructured data from a
remote endpoint. They also enable a mobile developer to store unique
key-value pairs without needing to check the data for uniqueness before
insertion.
Both Dictionaries and Maps can be useful when working with REST APIs,
where extra data may be returned that's not defined in a mobile app's
schema. Mobile developers who need to future-proof their schema against
rapidly changing feature requirements and future product iterations will
also find it useful to work with these new data types in Realm.
Consider a gaming app that has multiple games within it, and a single
Player class. The developer building the app knows that future releases
will need to enable new functionality, like a view of player statistics
and a leaderboard. But the Player can serve in different roles for each
available game. This makes defining a strict structure for player
statistics difficult.
With Dictionary/Map data types, the developer can place a gameplayStats
field on the Player class as a dictionary. Using this dictionary, it's
simple to display a screen that shows the player's most common roles,
the games they've competed in, and any relevant statistics that the
developer wants to include on the leaderboard. After the leaderboard has
been released and iterated on, the developer can look to migrate their
Dictionary to a more formally structured class as part of a formal
feature.
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Realm's Mixed type allows any Realm primitive type to be stored in the
database, helping developers when strict type-safety isn't appropriate.
Developers may find this useful when dealing with data they don't have
total control over – like receiving data and values from a third-party
API. Mixed data types are also useful when dealing with legacy states
that were stored with the incorrect types. Converting the type could
break other APIs and create considerable work. With Mixed types,
developers can avoid this difficulty and save hours of time.
We believe Mixed data types will be especially valuable for users who
want to sync data between Realm and MongoDB Atlas. MongoDB's
document-based data model allows a single field to support many types
across documents. For users syncing data between Realm and Atlas, the
new Mixed type allows developers to persist data of any valid Realm
primitive type, or any Realm Object class reference. Developers don't
risk crashing their app because a field value violated type-safety rules
in Realm.
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Sets allow developers to store an unordered array of unique values. This
new data type in Realm opens up powerful querying and mutation
capabilities with only a few lines of code.
With sets, you can compare data and quickly find matches. Sets in Realm
have built-in methods for filtering and writing to a set that are unique
to the type. Unique methods on the Set type include, isSubset(),
contains(), intersects(), formIntersection, and formUnion(). Aggregation
functions like min(), max(), avg(), and sum() can be used to find
averages, sums, and similar.
Sets in Realm have the potential to eliminate hundreds of lines of
gluecode. Consider an app that suggests expert speakers from different
areas of study, who can address a variety of specific topics. The
developer creates two classes for this use case: Expert and Topic. Each
of these classes has a Set field of strings which defines the
disciplines the user is an expert in, and the fields that the topic
covers.
Sets will make the predicted queries easy for the developer to
implement. An app user who is planning a Speaker Panel could see all
experts who have knowledge of both "Autonomous Vehicles" and "City
Planning." The application could also run a query that looks for experts
in one or more of these disciples by using the built-in intersect
method, and the user can use results to assemble a speaker panel.
Developers who are using MongoDB Realm
Sync to keep data up-to-date
between Realm and MongoDB Atlas are able to keep the semantics of a Set
in place even when synchronizing data.
You can depend on the enforced uniqueness among the values of a Set.
There's no need to check the array for a value match before performing
an insertion, which is a common implementation pattern that any user of
SQLite will be familiar with. The operations performed on Realm Set data
types will be synced and translated to documents using the
$addToSet
group of operations on MongoDB, preserving uniqueness in arrays.
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The Realm SDKs also now support the ability to generate and persist
Universally Unique Identifiers (UUIDs) natively. UUIDs are ubiquitous in
app development as the most common type used for primary keys. As a
128-bit value, they have become the default for distributed storage of
data in mobile to cloud application architectures - making collisions
unheard of.
Previously, Realm developers would generate a UUID and then cast it as a
string to store in Realm. But we saw an opportunity to eliminate
repetitive code, and with the release of UUID data types, Realm comes
one step closer to boilerplate-free code.
Like with the other new data types, the release of UUIDs also brings
Realm's data types to parity with MongoDB. Now mobile application
developers will be able to set UUIDs on both ends of their distributed
datastore, and can rely on Realm Sync to perform the replication.
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From the beginning, Realm's engineering team has believed that the best
line of code is the one a developer doesn't need to write. With the
release of these unique types for mobile developers, we're eliminating
the workarounds – the boilerplate code and negative impact on CPU and
memory – that are commonly required with certain data structures. And
we're doing it in a way that's idiomatic to the platform you're building
on.
By making it simple to query, store, and sync your data, all in the
format you need, we hope we've made it easier for you to focus on
building your next great app.
Want to be notified about upcoming Realm events, like talks on SwiftUI
Best Practices or our new Kotlin Multiplatform SDK? Visit our Global
Community Page.