RxRealm
This library is a thin wrapper around RealmSwift ( Realm Docs ).
Table of contents:
- Observing object collections
- Observing a single object
- Write transactions
- Automatically binding table and collection views
- Example app
Observing object collections
RxRealm can be used to create Observables from objects of type Results, List, LinkingObjects or AnyRealmCollection. These types are typically used to load and observe object collections from the Realm Mobile Database.
Observable.collection(from:synchronousStart:)
Emits an event each time the collection changes:
let realm = try! Realm()
let laps = realm.objects(Lap.self)
Observable.collection(from: laps)
.map {
laps in "\(laps.count) laps"
}
.subscribe(onNext: { text in
print(text)
})
The above prints out "X laps" each time a lap is added or removed from the database. If you set synchronousStart to true (the default value), the first element will be emitted synchronously - e.g. when you're binding UI it might not be possible for an asynchronous notification to come through.
Observable.array(from:synchronousStart:)
Upon each change fetches a snapshot of the Realm collection and converts it to an array value (for example if you want to use array methods on the collection):
let realm = try! Realm()
let laps = realm.objects(Lap.self)
Observable.array(from: laps)
.map { array in
return array.prefix(3) //slice of first 3 items
}
.subscribe(onNext: { text in
print(text)
})
Observable.changeset(from:synchronousStart:)
Emits every time the collection changes and provides the exact indexes that has been deleted, inserted or updated:
let realm = try! Realm()
let laps = realm.objects(Lap.self)
Observable.changeset(from: laps)
.subscribe(onNext: { results, changes in
if let changes = changes {
// it's an update
print(results)
print("deleted: \(changes.deleted)")
print("inserted: \(changes.inserted)")
print("updated: \(changes.updated)")
} else {
// it's the initial data
print(results)
}
})
Observable.arrayWithChangeset(from:synchronousStart:)
Combines the result of Observable.array(from:) and Observable.changeset(from:) returning an Observable<Array<T>, RealmChangeset?>
let realm = try! Realm()
let laps = realm.objects(Lap.self))
Observable.arrayWithChangeset(from: laps)
.subscribe(onNext: { array, changes in
if let changes = changes {
// it's an update
print(array.first)
print("deleted: \(changes.deleted)")
print("inserted: \(changes.inserted)")
print("updated: \(changes.updated)")
} else {
// it's the initial data
print(array)
}
})
Observing a single object
There's a separate API to make it easier to observe a single object:
Observable.from(object: ticker)
.map { ticker -> String in
return "\(ticker.ticks) ticks"
}
.bindTo(footer.rx.text)
This API uses the Realm object notifications under the hood to listen for changes.
This method will by default emit the object initial state as its first next event. You can disable this behavior by using the emitInitialValue parameter and setting it to false.
Finally you can set changes to which properties constitute an object change you'd like to observe for:
Observable.from(object: ticker, properties: ["name", "id", "family"]) ...
Write transactions
rx.add()
Writing objects to existing realm reference. You can add newly created objects to a Realm that you already have initialized:
let realm = try! Realm()
let messages = [Message("hello"), Message("world")]
Observable.from(messages)
.subscribe(realm.rx.add())
Be careful, this will retain your Realm until the Observable completes or errors out.
Realm.rx.add()
Writing to the default Realm. You can leave it to RxRealm to grab the default Realm on any thread your subscribe and write objects to it:
let messages = [Message("hello"), Message("world")]
Observable.from(messages)
.subscribe(Realm.rx.add())
Realm.rx.add(configuration:)
Writing to a custom Realm. If you want to switch threads and not use the default Realm, provide a Realm.Configuration. You an also provide an error handler for the observer to be called if either creating the realm reference or the write transaction raise an error:
var config = Realm.Configuration()
/* custom configuration settings */
let messages = [Message("hello"), Message("world")]
Observable.from(messages)
.observeOn( /* you can switch threads here */ )
.subscribe(Realm.rx.add(configuration: config, onError: {elements, error in
if let elements = elements {
print("Error \(error.localizedDescription) while saving objects \(String(describing: elements))")
} else {
print("Error \(error.localizedDescription) while opening realm.")
}
}))
If you want to create a Realm on a different thread manually, allowing you to handle errors, you can do that too:
let messages = [Message("hello"), Message("world")]
Observable.from(messages)
.observeOn( /* you can switch threads here */ )
.subscribe(onNext: {messages in
let realm = try! Realm()
try! realm.write {
realm.add(messages)
}
})
rx.delete()
Deleting object(s) from an existing realm reference:
let realm = try! Realm()
let messages = realm.objects(Message.self)
Observable.from(messages)
.subscribe(realm.rx.delete())
Be careful, this will retain your realm until the Observable completes or errors out.
Realm.rx.delete()
Deleting from the object's realm automatically. You can leave it to RxRealm to grab the Realm from the first object and use it:
Observable.from(someCollectionOfPersistedObjects)
.subscribe(Realm.rx.delete())
Automatically binding table and collection views
RxRealm does not depend on UIKit/Cocoa and it doesn't provide built-in way to bind Realm collections to UI components.
a) Non-animated binding
You can use the built-in RxCocoa bindTo(_:) method, which will automatically drive your table view from your Realm results:
Observable.from( [Realm collection] )
.bindTo(tableView.rx.items) {tv, ip, element in
let cell = tv.dequeueReusableCell(withIdentifier: "Cell")!
cell.textLabel?.text = element.text
return cell
}
.addDisposableTo(bag)
b) Animated binding with RxRealmDataSources
The separate library RxRealmDataSources mimics the default data sources library behavior for RxSwift.
RxRealmDataSources allows you to bind an observable collection of Realm objects directly to a table or collection view:
// create data source
let dataSource = RxTableViewRealmDataSource<Lap>(
cellIdentifier: "Cell", cellType: PersonCell.self) {cell, ip, lap in
cell.customLabel.text = "\(ip.row). \(lap.text)"
}
// RxRealm to get Observable<Results>
let realm = try! Realm()
let lapsList = realm.objects(Timer.self).first!.laps
let laps = Observable.changeset(from: lapsList)
// bind to table view
laps
.bindTo(tableView.rx.realmChanges(dataSource))
.addDisposableTo(bag)
The data source will reflect all changes via animations to the table view:
If you want to learn more about the features beyond animating changes, check the RxRealmDataSources README.
Example app
To run the example project, clone the repo, and run pod install from the Example directory first. The app uses RxSwift, RxCocoa using RealmSwift, RxRealm to observe Results from Realm.
Further you're welcome to peak into the RxRealmTests folder of the example app, which features the library's unit tests.
Installation
This library depends on both RxSwift and RealmSwift 1.0+.
CocoaPods
RxRealm requires CocoaPods 1.1.x or higher.
RxRealm is available through CocoaPods. To install it, simply add the following line to your Podfile:
pod "RxRealm"
Carthage
To integrate RxRealm into your Xcode project using Carthage, specify it in your Cartfile:
github "RxSwiftCommunity/RxRealm"
Run carthage update to build the framework and drag the built RxRealm.framework into your Xcode project.
Swift Package Manager
In your Package.swift:
let package = Package(
name: "Example",
dependencies: [
.package(url: "https://github.com/RxSwiftCommunity/RxRealm.git", from: "1.0.1")
],
targets: [
.target(name: "Example", dependencies: ["RxRealm"])
]
)
TODO
- Test add platforms and add compatibility for the pod
License
This library belongs to RxSwiftCommunity. Maintainer is Marin Todorov.
RxRealm is available under the MIT license. See the LICENSE file for more info.
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