Initial Commit

Package.resolved

@@ -0,0 +1,25 @@
+{
+  "object": {
+    "pins": [
+      {
+        "package": "Chain",
+        "repositoryURL": "https://github.com/0xLeif/Chain",
+        "state": {
+          "branch": null,
+          "revision": "a431a470148372639c9a35dce4c04b30fd7adc60",
+          "version": "0.2.0"
+        }
+      },
+      {
+        "package": "E",
+        "repositoryURL": "https://github.com/0xLeif/E.num",
+        "state": {
+          "branch": null,
+          "revision": "a4b2b0cf453edf2e2b3853cdcdd7c8596cadbf43",
+          "version": "0.3.0"
+        }
+      }
+    ]
+  },
+  "version": 1
+}

Package.swift

@@ -14,13 +14,16 @@ let package = Package(
     dependencies: [
         // Dependencies declare other packages that this package depends on.
         // .package(url: /* package url */, from: "1.0.0"),
+        .package(url: "https://github.com/0xLeif/Chain", from: "0.2.0")
     ],
     targets: [
         // Targets are the basic building blocks of a package. A target can define a module or a test suite.
         // Targets can depend on other targets in this package, and on products in packages this package depends on.
         .target(
             name: "Observation",
-            dependencies: []),
+            dependencies: [
+                "Chain"
+            ]),
         .testTarget(
             name: "ObservationTests",
             dependencies: ["Observation"]),

README.md

@@ -1,3 +1,20 @@
 # Observation
 
-A description of this package.
+
+## Example Code
+
+```swift
+let observedValue: ObservedValue<Int> = ObservedValue()
+
+observedValue.didChangeHandler = .complete(
+    .void {
+        sleep(1)
+        print("Done!")
+        XCTAssertNotNil(observedValue.value)
+    }
+)
+
+observedValue.update(value: 5)
+observedValue.update(value: 15)
+observedValue.update(value: 25)
+```

Sources/Observation/Observation.swift

@@ -1,3 +0,0 @@
-struct Observation {
-    var text = "Hello, World!"
-}

Sources/Observation/ObservedValue.swift

@@ -0,0 +1,36 @@
+import Chain
+
+@propertyWrapper public struct Observed<T> {
+    private var observedValue = ObservedValue<T>()
+    
+    public var didChangeHandler: Chain? {
+        didSet {
+            observedValue.didChangeHandler = didChangeHandler
+        }
+    }
+    public var wrappedValue: T {
+        didSet {
+            observedValue.update(value: wrappedValue)
+        }
+    }
+
+    public init(wrappedValue: T) {
+        self.wrappedValue = wrappedValue
+    }
+}
+
+public class ObservedValue<T> {
+    private(set) var value: T?
+    
+    public var didChangeHandler: Chain?
+    
+    public init(value: T? = nil) {
+        self.value = value
+    }
+    
+    public func update(value: T) {
+        self.value = value
+        
+        _ = didChangeHandler?.run(name: "")
+    }
+}

Tests/ObservationTests/ObservationTests.swift

@@ -2,11 +2,25 @@ import XCTest
 @testable import Observation
 
 final class ObservationTests: XCTestCase {
+    @Observed var ov = 4
+    
     func testExample() {
-        // This is an example of a functional test case.
-        // Use XCTAssert and related functions to verify your tests produce the correct
-        // results.
-        XCTAssertEqual(Observation().text, "Hello, World!")
+        
+        let observedValue: ObservedValue<Int> = ObservedValue()
+        
+        observedValue.didChangeHandler = .complete(
+            .void {
+                sleep(1)
+                print("Done!")
+                XCTAssertNotNil(observedValue.value)
+            }
+        )
+
+        observedValue.update(value: 5)
+        observedValue.update(value: 15)
+        observedValue.update(value: 25)
+        
+        XCTAssertEqual(observedValue.value, 25)
     }
     
     static var allTests = [