Store createdAt and updatedAt as TimeIntervalSince1970 in DynamoDB

Author: Andrea-Scuderi

Examples/LambdaFunctions/Sources/ProductAPI/Product+DynamoDB.swift

@@ -13,6 +13,7 @@
 //===----------------------------------------------------------------------===//
 
 import AWSDynamoDB
+import Foundation
 
 extension Product {
 
@@ -22,12 +23,12 @@ extension Product {
             Field.name: DynamoDB.AttributeValue(s: name),
             Field.description: DynamoDB.AttributeValue(s: description),
         ]
-        if let createdAt = createdAt {
-            dictionary[Field.createdAt] = DynamoDB.AttributeValue(s: createdAt)
+        if let createdAt = createdAt?.timeIntervalSince1970String {
+            dictionary[Field.createdAt] = DynamoDB.AttributeValue(n: createdAt)
         }
 
-        if let updatedAt = updatedAt {
-            dictionary[Field.updatedAt] = DynamoDB.AttributeValue(s: updatedAt)
+        if let updatedAt = updatedAt?.timeIntervalSince1970String {
+            dictionary[Field.updatedAt] = DynamoDB.AttributeValue(n: updatedAt)
         }
         return dictionary
     }
@@ -42,7 +43,15 @@ extension Product {
         self.name = name
         self.sku = sku
         self.description = description
-        self.createdAt = dictionary[Field.createdAt]?.s
-        self.updatedAt = dictionary[Field.updatedAt]?.s
+        if let value = dictionary[Field.createdAt]?.n,
+            let timeInterval = TimeInterval(value) {
+            let date = Date(timeIntervalSince1970: timeInterval)
+            self.createdAt = date.iso8601
+        }
+        if let value = dictionary[Field.updatedAt]?.n,
+            let timeInterval = TimeInterval(value) {
+            let date = Date(timeIntervalSince1970: timeInterval)
+            self.updatedAt = date.iso8601
+        }
     }
 }

Examples/LambdaFunctions/Sources/ProductAPI/ProductService.swift

@@ -39,6 +39,20 @@ extension Date {
     }
 }
 
+extension String {
+    var iso8601: Date? {
+        let formatter = DateFormatter.iso8061
+        return formatter.date(from: self)
+    }
+    
+    var timeIntervalSince1970String: String? {
+        guard let timeInterval = self.iso8601?.timeIntervalSince1970 else {
+            return nil
+        }
+        return "\(timeInterval)"
+    }
+}
+
 public class ProductService {
 
     let db: DynamoDB
@@ -78,18 +92,21 @@ public class ProductService {
     public func updateItem(product: Product) -> EventLoopFuture<Product> {
         var product = product
         let date = Date()
+        let updatedAt = "\(date.timeIntervalSince1970)"
         product.updatedAt = date.iso8601
 
         let input = DynamoDB.UpdateItemInput(
+            conditionExpression: "attribute_exists(#createdAt)",
             expressionAttributeNames: [
                 "#name": Product.Field.name,
                 "#description": Product.Field.description,
                 "#updatedAt": Product.Field.updatedAt,
+                "#createdAt": Product.Field.createdAt
             ],
             expressionAttributeValues: [
                 ":name": DynamoDB.AttributeValue(s: product.name),
                 ":description": DynamoDB.AttributeValue(s: product.description),
-                ":updatedAt": DynamoDB.AttributeValue(s: product.updatedAt),
+                ":updatedAt": DynamoDB.AttributeValue(n: updatedAt)
             ],
             key: [Product.Field.sku: DynamoDB.AttributeValue(s: product.sku)],
             returnValues: DynamoDB.ReturnValue.allNew,