add swift package, and remove OBJC code in Swift files

Mixpanel/Persistence.swift

@@ -159,15 +159,10 @@ class Persistence {
             return
         }
 
-        ExceptionWrapper.try({ [cObject = archiveObject, cPath = path, cType = type] in
-            if !NSKeyedArchiver.archiveRootObject(cObject, toFile: cPath) {
-                Logger.error(message: "failed to archive \(cType.rawValue)")
-                return
-            }
-        }, catch: { [cType = type] (error) in
-            Logger.error(message: "failed to archive \(cType.rawValue) due to an uncaught exception")
+        if !NSKeyedArchiver.archiveRootObject(archiveObject, toFile: path) {
+            Logger.error(message: "failed to archive \(type.rawValue)")
             return
-        }, finally: {})
+        }
 
         addSkipBackupAttributeToItem(at: path)
     }
@@ -283,16 +278,11 @@ class Persistence {
 
     static private func unarchiveWithFilePath(_ filePath: String) -> Any? {
         var unarchivedData: Any? = nil
-        ExceptionWrapper.try({ [filePath] in
-            unarchivedData = NSKeyedUnarchiver.unarchiveObject(withFile: filePath)
-            if unarchivedData == nil {
-                Logger.info(message: "Unable to read file at path: \(filePath)")
-                removeArchivedFile(atPath: filePath)
-            }
-        }, catch: { [filePath] (error) in
+        unarchivedData = NSKeyedUnarchiver.unarchiveObject(withFile: filePath)
+        if unarchivedData == nil {
+            Logger.info(message: "Unable to read file at path: \(filePath)")
             removeArchivedFile(atPath: filePath)
-            Logger.info(message: "Unable to read file at path: \(filePath), error: \(String(describing: error))")
-        }, finally: {})
+        }
         return unarchivedData
     }
 

Package.swift

@@ -0,0 +1,32 @@
+// swift-tools-version:5.3
+// The swift-tools-version declares the minimum version of Swift required to build this package.
+
+import PackageDescription
+
+let package = Package(
+  name: "Mixpanel",
+  platforms: [
+    .iOS(.v8),
+    .tvOS(.v9),
+    .macOS(.v10_10),
+    .watchOS(.v3),
+  ],
+  products: [
+    // Products define the executables and libraries produced by a package, and make them visible to other packages.
+    .library(
+      name: "Mixpanel",
+      targets: ["Mixpanel"])
+  ],
+  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 which this package depends on.
+    .target(
+      name: "Mixpanel",
+      dependencies: [],
+      path: "Mixpanel"),
+  ]
+)