Improve catching of Swift Errors.

Disk.xcodeproj/project.pbxproj

@@ -23,6 +23,8 @@
 		10F3C7041F23D9C9006D42EF /* Disk+Data.swift in Sources */ = {isa = PBXBuildFile; fileRef = 10F3C7031F23D9C9006D42EF /* Disk+Data.swift */; };
 		10F3C7061F23D9E0006D42EF /* Disk+[Data].swift in Sources */ = {isa = PBXBuildFile; fileRef = 10F3C7051F23D9E0006D42EF /* Disk+[Data].swift */; };
 		10F3C7081F23DAF2006D42EF /* Message.swift in Sources */ = {isa = PBXBuildFile; fileRef = 10F3C7071F23DAF2006D42EF /* Message.swift */; };
+		261E777E2178916800B7DFB6 /* DiskErrors.m in Sources */ = {isa = PBXBuildFile; fileRef = 261E777D2178916800B7DFB6 /* DiskErrors.m */; };
+		261E777F21789EB900B7DFB6 /* DiskErrors.h in Headers */ = {isa = PBXBuildFile; fileRef = 261E777C2178912C00B7DFB6 /* DiskErrors.h */; settings = {ATTRIBUTES = (Public, ); }; };
 /* End PBXBuildFile section */
 
 /* Begin PBXContainerItemProxy section */
@@ -55,6 +57,8 @@
 		10F3C7031F23D9C9006D42EF /* Disk+Data.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = "Disk+Data.swift"; sourceTree = "<group>"; };
 		10F3C7051F23D9E0006D42EF /* Disk+[Data].swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = "Disk+[Data].swift"; sourceTree = "<group>"; };
 		10F3C7071F23DAF2006D42EF /* Message.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = Message.swift; sourceTree = "<group>"; };
+		261E777C2178912C00B7DFB6 /* DiskErrors.h */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.c.h; path = DiskErrors.h; sourceTree = "<group>"; };
+		261E777D2178916800B7DFB6 /* DiskErrors.m */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.c.objc; path = DiskErrors.m; sourceTree = "<group>"; };
 /* End PBXFileReference section */
 
 /* Begin PBXFrameworksBuildPhase section */
@@ -103,6 +107,8 @@
 				103FA3761F713332004C600F /* Disk+InternalHelpers.swift */,
 				103FA3781F713340004C600F /* Disk+VolumeInformation.swift */,
 				104611771F27B27E00BBDB3A /* Disk+Errors.swift */,
+				261E777C2178912C00B7DFB6 /* DiskErrors.h */,
+				261E777D2178916800B7DFB6 /* DiskErrors.m */,
 				109256591F247F7700B3C32A /* Disk+Helpers.swift */,
 				10F3C6FD1F23D9A4006D42EF /* Disk+Codable.swift */,
 				10F3C6FF1F23D9B1006D42EF /* Disk+UIImage.swift */,
@@ -132,6 +138,7 @@
 			isa = PBXHeadersBuildPhase;
 			buildActionMask = 2147483647;
 			files = (
+				261E777F21789EB900B7DFB6 /* DiskErrors.h in Headers */,
 				10F3C6F21F23D984006D42EF /* Disk.h in Headers */,
 			);
 			runOnlyForDeploymentPostprocessing = 0;
@@ -187,7 +194,7 @@
 				TargetAttributes = {
 					10F3C6E01F23D984006D42EF = {
 						CreatedOnToolsVersion = 9.0;
-						LastSwiftMigration = 0900;
+						LastSwiftMigration = 1010;
 					};
 					10F3C6E91F23D984006D42EF = {
 						CreatedOnToolsVersion = 9.0;
@@ -245,6 +252,7 @@
 				10F3C7041F23D9C9006D42EF /* Disk+Data.swift in Sources */,
 				103FA3791F713340004C600F /* Disk+VolumeInformation.swift in Sources */,
 				10F3C7001F23D9B1006D42EF /* Disk+UIImage.swift in Sources */,
+				261E777E2178916800B7DFB6 /* DiskErrors.m in Sources */,
 				104611781F27B27E00BBDB3A /* Disk+Errors.swift in Sources */,
 			);
 			runOnlyForDeploymentPostprocessing = 0;

DiskExample/DiskExample/ViewController.swift

@@ -66,7 +66,8 @@ class ViewController: UIViewController {
     @IBAction func retrieveTapped(_ sender: Any) {
         // We'll keep things simple here by using try?, but it's good practice to handle Disk with do, catch, try blocks
         // so you can make sure everything is going according to plan.
-        if let retrievedPosts = try? Disk.retrieve("posts.json", from: .documents, as: [Post].self) {
+        do {
+            let retrievedPosts = try Disk.retrieve("posts.json", from: .documents, as: [Post].self)
             // If you Option+Click 'retrievedPosts' above, you'll notice that its type is [Post]
             // Pretty neat, huh?
 
@@ -77,6 +78,17 @@ class ViewController: UIViewController {
             self.resultsTextView.text = result
 
             print("Retrieved posts from disk!")
+        } catch DiskError.noFileFound {
+            self.resultsTextView.text = "No file saved to disk yet!"
+            print ("No file found to retrieve posts from.")
+        } catch let error as NSError {
+            fatalError("""
+                Domain: \(error.domain)
+                Code: \(error.code)
+                Description: \(error.localizedDescription)
+                Failure Reason: \(error.localizedFailureReason ?? "")
+                Suggestions: \(error.localizedRecoverySuggestion ?? "")
+                """)
         }
     }
 

README.md

@@ -401,6 +401,8 @@ do {
     if Disk.exists("posts.json", in: .documents) {
         try Disk.remove("posts.json", from: .documents)
     }
+} catch DiskError.noFileFound {
+    // Pattern matching to catch specific errors.
 } catch let error as NSError {
     fatalError("""
         Domain: \(error.domain)

Sources/Disk+Errors.swift

@@ -23,24 +23,13 @@
 import Foundation
 
 extension Disk {
-    public enum ErrorCode: Int {
-        case noFileFound = 0
-        case serialization = 1
-        case deserialization = 2
-        case invalidFileName = 3
-        case couldNotAccessTemporaryDirectory = 4
-        case couldNotAccessUserDomainMask = 5
-        case couldNotAccessSharedContainer = 6
-    }
-
-    public static let errorDomain = "DiskErrorDomain"
 
     /// Create custom error that FileManager can't account for
-    static func createError(_ errorCode: ErrorCode, description: String?, failureReason: String?, recoverySuggestion: String?) -> Error {
+    static func createError(_ errorCode: DiskError.Code, description: String?, failureReason: String?, recoverySuggestion: String?) -> DiskError {
         let errorInfo: [String: Any] = [NSLocalizedDescriptionKey : description ?? "",
                                         NSLocalizedRecoverySuggestionErrorKey: recoverySuggestion ?? "",
                                         NSLocalizedFailureReasonErrorKey: failureReason ?? ""]
-        return NSError(domain: errorDomain, code: errorCode.rawValue, userInfo: errorInfo) as Error
+        return NSError(domain: DiskErrorDomain, code: errorCode.rawValue, userInfo: errorInfo) as! DiskError
     }
 }
 

Sources/Disk.h

@@ -28,4 +28,4 @@ FOUNDATION_EXPORT double DiskVersionNumber;
 //! Project version string for Disk.
 FOUNDATION_EXPORT const unsigned char DiskVersionString[];
 
-
+#import "DiskErrors.h"

Sources/DiskErrors.h

@@ -0,0 +1,24 @@
+//
+//  DiskErrors.h
+//  Disk
+//
+//  Created by Sven Titgemeyer on 18.10.18.
+//  Copyright © 2018 Saoud Rizwan. All rights reserved.
+//
+
+#import <Foundation/Foundation.h>
+
+/// Domain for Disk Errors.
+///
+/// Define Errors in Objective-C to get better Bridging between Swift/Objective-C.
+/// Errors are imported as `DiskError` in Swift.
+extern NSErrorDomain const DiskErrorDomain;
+typedef NS_ERROR_ENUM(DiskErrorDomain, DiskError) {
+    DiskErrorNoFileFound = 0,
+    DiskErrorSerialization = 1,
+    DiskErrorDeserialization = 2,
+    DiskErrorInvalidFileName = 3,
+    DiskErrorCouldNotAccessTemporaryDirectory = 4,
+    DiskErrorCouldNotAccessUserDomainMask = 5,
+    DiskErrorCouldNotAccessSharedContainer = 6
+};

Sources/DiskErrors.m

@@ -0,0 +1,11 @@
+//
+//  DiskErrors.m
+//  Disk
+//
+//  Created by Sven Titgemeyer on 18.10.18.
+//  Copyright © 2018 Saoud Rizwan. All rights reserved.
+//
+
+#import "DiskErrors.h"
+
+NSErrorDomain const DiskErrorDomain = @"DiskErrorDomain";

Tests/DiskTests.swift

@@ -805,7 +805,8 @@ class DiskTests: XCTestCase {
             try Disk.append(oneMessage, to: "Folder/", in: .documents)
             let _ = try Disk.retrieve("Folder/", from: .documents, as: [Message].self)
         } catch let error as NSError {
-            XCTAssert(error.code == Disk.ErrorCode.invalidFileName.rawValue)
+            XCTAssert(error is DiskError)
+            XCTAssert(error.code == DiskError.invalidFileName.rawValue)
         }
     }