Best Practices for CRUD

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Querying Dynamic Data Using $args 
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Swift
Kotlin
JS
Java
C#
C++
Rust
let query = "color == $args.color"
let args = [ "color": "blue" ]
let documents = ditto.store
  .collection("your_collection_name")
  .find(query, args)
  .exec()
let query = "color == $args.color"
let args = [ "color": "blue" ]
let documents = ditto.store
  .collection("your_collection_name")
  .find(query, args)
  .exec()
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Batching Multiple Operations
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The following snippet demonstrates a batch operation in which two write transactions are contained in a single transaction enclosure:
Swift
Kotlin
JS
Java
C#
C++
Rust
val results = ditto.store.write { transaction ->
    val cars = transaction.scoped("cars")
    val people = transaction.scoped("people")
    val docId = "abc123"
    people.upsert(mapOf("_id" to docId, "name" to "Susan"))
    cars.upsert(mapOf("make" to "Hyundai", "color" to "red", "owner" to docId))
    cars.upsert(mapOf("make" to "Jeep", "color" to "pink", "owner" to docId))
    people.findById(DittoDocumentId(docId)).evict()
}
val results = ditto.store.write { transaction ->
    val cars = transaction.scoped("cars")
    val people = transaction.scoped("people")
    val docId = "abc123"
    people.upsert(mapOf("_id" to docId, "name" to "Susan"))
    cars.upsert(mapOf("make" to "Hyundai", "color" to "red", "owner" to docId))
    cars.upsert(mapOf("make" to "Jeep", "color" to "pink", "owner" to docId))
    people.findById(DittoDocumentId(docId)).evict()
}
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Using ISO-8601 for Date Strings
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Implementing Write Strategies
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Insert if Absent
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Swift
Kotlin
JS
Java
C#
C++
Rust
let initialDocument : [String: Any] = [
  "_id": "123456",
  "color": "blue"
]
let documentId = ditto.store
  .collection("cars")
  .upsert(initialDocument, writeStrategy: .insertIfAbsent)
let initialDocument : [String: Any] = [
  "_id": "123456",
  "color": "blue"
]
let documentId = ditto.store
  .collection("cars")
  .upsert(initialDocument, writeStrategy: .insertIfAbsent)
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Insert Default if Absent
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The following snippet shows an example of the writeStrategy: insertDefaultIfAbsent parameter passed as an argument to theupsert method:
Swift
Kotlin
JS
Java
C#
C++
Rust
do {
    let docID = try ditto.store["people"].upsert([
        "name": "Susan",
        "age": 31
    ], writeStrategy: .insertDefaultIfAbsent)
} catch {
    //handle error
    print(error)
}
do {
    let docID = try ditto.store["people"].upsert([
        "name": "Susan",
        "age": 31
    ], writeStrategy: .insertDefaultIfAbsent)
} catch {
    //handle error
    print(error)
}
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Example Use Case: Upserting Initial Data
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Implementing Global Async Transactions
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For example, use DispatchQueue.global, as follows:
Swift
Kotlin
JS
Java
C#
C++
Rust
DispatchQueue.global(qos: .default).async {

    ditto.store.write { transaction in

        let scope = transaction.scoped(toCollectionNamed: "passengers-\(thisFlight)")

    // Loop inside the transaction to avoid writing to database too frequently
        self.passengers.forEach {
            scope.upsert($0.dict)
        }
    }
}
DispatchQueue.global(qos: .default).async {

    ditto.store.write { transaction in

        let scope = transaction.scoped(toCollectionNamed: "passengers-\(thisFlight)")

    // Loop inside the transaction to avoid writing to database too frequently
        self.passengers.forEach {
            scope.upsert($0.dict)
        }
    }
}
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Avoiding Deadlocks
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Example of a Deadlock
The following snippet demonstrates a queued write transaction that has the potential to create a deadlock situation. This is because the write transaction initiated on the "people" collection, along with its nested write transaction on the "settings" collection both attempt to acquire resources held by the other:
Swift
Kotlin
JS
Java
C#
C++
Rust
// Start a write transaction:
ditto.store["people"].findByID(docID).update { mutableDoc in
  // Start a write transaction _within_ a write transacton.
  // !! Deadlocks !!
  let docID = try! ditto.store["settings"].upsert([
      "_id": "abc123",
      "preference": 31,
  ]) 
  // ...
}
// Start a write transaction:
ditto.store["people"].findByID(docID).update { mutableDoc in
  // Start a write transaction _within_ a write transacton.
  // !! Deadlocks !!
  let docID = try! ditto.store["settings"].upsert([
      "_id": "abc123",
      "preference": 31,
  ]) 
  // ...
}
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Log Message: Transaction Remains Blocked
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Updated 11 Mar 2024
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Evicting and Removing
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