Add _modify accessor to Atomic.value

CHANGELOG.md

@@ -1,5 +1,6 @@
 # master
 *Please add new entries at the top.*
+1. Add `_modify` accessor to `Atomic.value` (#731, kudos to @p4checo)
 
 # 6.0.0
 1. Dropped support for Swift 4.2 (Xcode 9)

Sources/Atomic.swift

@@ -226,6 +226,13 @@ public final class Atomic<Value> {
 		set(newValue) {
 			swap(newValue)
 		}
+
+		_modify {
+			lock.lock()
+			defer { lock.unlock() }
+
+			yield &_value
+		}
 	}
 
 	/// Initialize the variable with the given initial value.

Tests/ReactiveSwiftTests/AtomicSpec.swift

@@ -18,11 +18,14 @@ class AtomicSpec: QuickSpec {
 			atomic = Atomic(1)
 		}
 
-		it("should read and write the value directly") {
+		it("should read, write and modify the value directly") {
 			expect(atomic.value) == 1
 
 			atomic.value = 2
 			expect(atomic.value) == 2
+
+			atomic.value += 1
+			expect(atomic.value) == 3
 		}
 
 		it("should swap the value atomically") {