Add SPM support

Package.swift

@@ -0,0 +1,28 @@
+// swift-tools-version: 5.6
+// The swift-tools-version declares the minimum version of Swift required to build this package.
+
+import PackageDescription
+
+let package = Package(
+    name: "VanillaConstraints",
+    products: [
+        // Products define the executables and libraries a package produces, and make them visible to other packages.
+        .library(
+            name: "VanillaConstraints",
+            targets: ["VanillaConstraints"]),
+    ],
+    dependencies: [
+        // Dependencies declare other packages that this package depends on.
+        // .package(url: /* package url */, from: "1.0.0"),
+    ],
+    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: "VanillaConstraints",
+            dependencies: []),
+        .testTarget(
+            name: "VanillaConstraintsTests",
+            dependencies: ["VanillaConstraints"]),
+    ]
+)

VanillaConstraints/Source/Constrainable.swift → Sources/VanillaConstraints/Sources/Constrainable.swift

@@ -9,7 +9,7 @@
 import Foundation
 import UIKit
 
-public protocol Constrainable: class {
+public protocol Constrainable: AnyObject {
     var parent: UIView { get }
     var target: UIView { get }
 }

VanillaConstraints.podspec

@@ -6,9 +6,9 @@ Pod::Spec.new do |spec|
   spec.authors      = { 'Joan Disho' => 'dishojoan@gmail.com' }
   spec.summary      = 'Simplified and chainable AutoLayout NSLayoutConstraints for iOS.'
   spec.source       = { :git => 'https://github.com/jdisho/VanillaConstraints.git', :tag => spec.version }
-  spec.swift_version = '4.0'
+  spec.swift_version = '5.6'
   spec.ios.deployment_target = '9.0'
-  spec.source_files = 'VanillaConstraints/Source/*.swift'
+  spec.source_files = 'Sources/VanillaConstraints/**/*.swift'
   spec.framework  = 'Foundation'
   spec.framework  = 'UIKit'
 end