🪜 Ability to increment field values in Firestore

Author: benlmyers

Sources/EasyFirebase/Extensions/AdditiveArithmetic.swift

@@ -0,0 +1,14 @@
+//
+//  File.swift
+//  
+//
+//  Created by Ben Myers on 3/10/22.
+//
+
+import Foundation
+
+internal extension AdditiveArithmetic {
+  mutating func add(_ val: Self) {
+    self += val
+  }
+}

Sources/EasyFirebase/Services/Firestore/Protocols/Document.swift

@@ -122,6 +122,25 @@ extension Document {
     EasyFirestore.Storage.set(value, to: path, in: self, completion: completion)
   }
 
+  /**
+   Increments a specific field remotely in Firestore.
+   
+   - parameter path: The path to the field to update.
+   - parameter increment: The amount to increment by.
+   - parameter completion: The completion handler.
+   */
+  public mutating func increment<T>(_ path: WritableKeyPath<Self, T?>, by increment: T, completion: @escaping (Error?) -> Void = { _ in }) where T: AdditiveArithmetic {
+    let val = self[keyPath: path]
+    guard var val = val else { return }
+    if let intIncrement = increment as? Int {
+      EasyFirestore.Updating.increment(path, by: intIncrement, in: self, completion: completion)
+      val.add(increment)
+      self[keyPath: path] = val
+    } else {
+      fatalError("[EasyFirebase] You can't increment mismatching values! Check the types of values you are providing to increment.")
+    }
+  }
+  
   /**
    Gets the most up-to-date value from a specified path.
 
@@ -177,3 +196,4 @@ extension Document {
     EasyFirestore.Linking.unassign(self, from: path, in: parent, completion: completion)
   }
 }
+

Sources/EasyFirebase/Services/Firestore/Updating.swift

@@ -0,0 +1,36 @@
+//
+//  Updating.swift
+//  
+//
+//  Created by Ben Myers on 3/10/22.
+//
+
+import Foundation
+import Firebase
+import FirebaseFirestore
+import FirebaseFirestoreSwift
+
+@available(iOS 13.0, *)
+extension EasyFirestore {
+  
+  /**
+   A service used for storing objects in Firestore.
+   */
+  public struct Updating {
+    
+    // MARK: - Public Static Methods
+    
+    /**
+     Increments a value for a particular field in Firestore.
+     
+     - parameter path: The path to the document's field to update.
+     - parameter increase: The amount to increase.
+     - parameter document: The document with the updated field.
+     - parameter completion: The completion handler.
+     */
+    public static func increment<T, U>(_ path: KeyPath<T, U?>, by increase: Int, in document: T, completion: @escaping (Error?) -> Void = { _ in }) where T: Document, U: AdditiveArithmetic {
+      let collectionName = String(describing: T.self)
+      db.collection(collectionName).document(document.id).updateData([path.string: FieldValue.increment(Int64(increase))], completion: completion)
+    }
+  }
+}