Document conditional operations

src/main/resources/microsite/data/menu.yml

@@ -21,6 +21,9 @@ options:
   - title: Batch Operations
     url: batch-operations.html
 
+  - title: Conditional Operations
+    url: conditional-operations.html
+
   - title: Using Indexes
     url: using-indexes.html
 

src/main/tut/asynchronous.md

@@ -1,7 +1,7 @@
 ---
 layout: docs
 title: Asynchronous Requests
-position: 5
+position: 6
 ---
 
 ## Non-blocking requests

src/main/tut/conditional-operations.md

@@ -0,0 +1,47 @@
+---
+layout: docs
+title: Conditional Operations
+position: 3
+---
+
+## Conditional Operations
+
+Modifying operations ([Put](operations.html#put-and-get), [Delete](operations.html#delete),
+[Update](operations.html#update)) can be performed conditionally, so that they
+only have an effect if some state of the DynamoDB table is true at the time of 
+execution.
+
+```tut:silent
+import com.gu.scanamo._
+import com.gu.scanamo.syntax._
+import com.amazonaws.services.dynamodbv2.model.ScalarAttributeType._
+val client = LocalDynamoDB.client()
+case class Gremlin(number: Int, name: String, wet: Boolean, friendly: Boolean)
+```
+```tut:book
+val gremlinsTable = Table[Gremlin]("gremlins")
+LocalDynamoDB.withTable(client)("gremlins")('number -> N) {
+  val ops = for {
+    _ <- gremlinsTable.putAll(
+      Set(Gremlin(1, "Gizmo", false, true), Gremlin(2, "George", true, false)))
+    // Only `put` Gremlins if not already one with the same number
+    _ <- gremlinsTable.given(not(attributeExists('number)))
+      .put(Gremlin(2, "Stripe", false, true))
+    _ <- gremlinsTable.given(not(attributeExists('number)))
+      .put(Gremlin(3, "Greta", true, true))
+    allGremlins <- gremlinsTable.scan()  
+    _ <- gremlinsTable.given('wet -> true)
+      .delete('number -> 1)
+    _ <- gremlinsTable.given('wet -> true)
+      .delete('number -> 2)
+    _ <- gremlinsTable.given('wet -> true)
+      .update('number -> 1, set('friendly -> false))
+    _ <- gremlinsTable.given('wet -> true)
+      .update('number -> 3, set('friendly -> false))
+    remainingGremlins <- gremlinsTable.scan()
+  } yield (allGremlins, remainingGremlins)
+  Scanamo.exec(client)(ops)
+}
+```
+
+More examples can be found in the [Table ScalaDoc](/scanamo/latest/api/com/gu/scanamo/Table.html#given[T](condition:T)(implicitevidence$2:com.gu.scanamo.query.ConditionExpression[T]):com.gu.scanamo.query.ConditionalOperation[V,T]).

src/main/tut/dynamo-format.md

@@ -1,7 +1,7 @@
 ---
 layout: docs
 title: DynamoFormat
-position:  4
+position:  5
 ---
 
 ## DynamoFormat

src/main/tut/operations.md

@@ -17,8 +17,8 @@ Scanamo supports all the DynamoDB operations that interact with individual items
  * [Query](#query) for retrieving all elements with a given hash-key and a range key that matches
  some criteria
 
-Scanamo also supports [batched operations](batch-operations.html) and queries against 
-[secondary indexes](using-indexes.html).
+Scanamo also supports [batched operations](batch-operations.html), [conditional operations](conditional-operations.html) 
+and queries against [secondary indexes](using-indexes.html).
 
 ### Put and Get
 

src/main/tut/using-indexes.md

@@ -1,7 +1,7 @@
 ---
 layout: docs
 title: Using Indexes
-position: 3
+position: 4
 ---
 
 ## Using Indexes