(ref): Move SentryEventDecodable to Swift

Author: noahsmartin

Sources/Sentry/Public/SentryEvent.h

@@ -181,7 +181,7 @@ NS_SWIFT_NAME(Event)
 /**
  * Init an @c SentryEvent will set all needed fields by default.
  */
-- (instancetype)init;
+- (instancetype)init NS_DESIGNATED_INITIALIZER;
 
 /**
  * Init a @c SentryEvent with a @c SentryLevelError and set all needed fields by default.
@@ -196,24 +196,4 @@ NS_SWIFT_NAME(Event)
 
 @end
 
-/**
- * Subclass of SentryEvent so we can add the Decodable implementation via a Swift extension. We need
- * this due to our mixed use of public Swift and ObjC classes. We could avoid this class by
- * converting SentryReplayEvent back to ObjC, but we rather accept this tradeoff as we want to
- * convert all public classes to Swift in the future. This class needs to be public as we can't add
- * the Decodable extension implementation to a class that is not public.
- *
- * @note: We can’t add the extension for Decodable directly on SentryEvent, because we get an error
- * in SentryReplayEvent: 'required' initializer 'init(from:)' must be provided by subclass of
- * 'Event' Once we add the initializer with required convenience public init(from decoder: any
- * Decoder) throws { fatalError("init(from:) has not been implemented")
- * }
- * we get the error initializer 'init(from:)' is declared in extension of 'Event' and cannot be
- * overridden. Therefore, we add the Decodable implementation not on the Event, but to a subclass of
- * the event.
- */
-@interface SentryEventDecodable : SentryEvent
-
-@end
-
 NS_ASSUME_NONNULL_END

Sources/Sentry/SentryEvent.m

@@ -25,14 +25,23 @@
 
 @implementation SentryEvent
 
+// This is a designated initializer so that it can be called by the Swift
+// sublcass that adds a `Decodable` conformance. It shares an implementation
+// with `initWithLevel:`.
 - (instancetype)init
 {
-    return [self initWithLevel:kSentryLevelNone];
+    self = [super init];
+    return [self commonInit:kSentryLevelNone];
 }
 
 - (instancetype)initWithLevel:(enum SentryLevel)level
 {
     self = [super init];
+    return [self commonInit:level];
+}
+
+- (instancetype)commonInit:(enum SentryLevel)level
+{
     if (self) {
         self.eventId = [[SentryId alloc] init];
         self.level = level;
@@ -210,8 +219,4 @@ - (BOOL)isAppHangEvent
 
 @end
 
-@implementation SentryEventDecodable
-
-@end
-
 NS_ASSUME_NONNULL_END

Sources/Swift/Protocol/Codable/SentryEventCodable.swift

@@ -1,7 +1,25 @@
 @_implementationOnly import _SentryPrivate
 import Foundation
 
-extension SentryEventDecodable: Decodable {
+/**
+ * Subclass of SentryEvent so we can add the Decodable implementation via a Swift extension. We need
+ * this due to our mixed use of public Swift and ObjC classes. We could avoid this class by
+ * converting SentryReplayEvent back to ObjC, but we rather accept this tradeoff as we want to
+ * convert all public classes to Swift in the future. This does not need to be public, but was previously
+ * defined in objc and was public. In the next major version of the SDK we should make it `internal` and `final`
+ * and remove the `@objc` annotation.
+ *
+ * @note: We can’t add the extension for Decodable directly on SentryEvent, because we get an error
+ * in SentryReplayEvent: 'required' initializer 'init(from:)' must be provided by subclass of
+ * 'Event' Once we add the initializer with required convenience public init(from decoder: any
+ * Decoder) throws { fatalError("init(from:) has not been implemented")
+ * }
+ * we get the error initializer 'init(from:)' is declared in extension of 'Event' and cannot be
+ * overridden. Therefore, we add the Decodable implementation not on the Event, but to a subclass of
+ * the event.
+ */
+@objc(SentryEventDecodable)
+public class SentryEventDecodable: Event, Decodable {
 
     private enum CodingKeys: String, CodingKey {
         case eventId = "event_id"