for subclasses: decode the discriminator first, and only try decoding…

… the sub-object for the matching discriminator value
onvista-media · Oct 11, 2024 · 5c99ec0 · 5c99ec0
1 parent 07bebbb
commit 5c99ec0
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Showing 3 changed files with 32 additions and 22 deletions.
diff --git a/Sources/Generator.swift b/Sources/Generator.swift
@@ -288,12 +288,15 @@ final class Generator {
         let discriminatorType = schema.properties?[discriminator.propertyName]
 
         let discriminatorIsString: Bool
+        let discriminatorTypeName: String
         switch discriminatorType {
-        case .ref:
+        case .ref(let ref):
             discriminatorIsString = false
+            discriminatorTypeName = ref.swiftType().name
         case .property(let prop):
             assert(prop.type == "string", "\(modelName): unexpected discriminator type")
             discriminatorIsString = true
+            discriminatorTypeName = "String"
         case .none:
             fatalError("\(modelName): unknown discriminator type")
         }
@@ -322,22 +325,25 @@ final class Generator {
             }
             print("")
 
+            block("enum DiscriminatorKeys: String, CodingKey") {
+                print(#"case type = "\#(discriminator.propertyName)""#)
+            }
+            print("")
+
             // init method
             block("public init(from decoder: Decoder) throws") {
+                print("let container = try decoder.container(keyedBy: DiscriminatorKeys.self)")
+                print("let type = try container.decode(\(discriminatorTypeName).self, forKey: .type)")
+                print("")
                 for dc in discriminatorCases {
                     let compare = discriminatorIsString ? #""\#(dc.rawString)""# : ".\(dc.enumCase)"
-                    print(#"if let obj = try? \#(dc.mappedModel)(from: decoder), obj.\#(discriminator.propertyName) == \#(compare) {"#)
+                    print("if type == \(compare), let obj = try? \(dc.mappedModel)(from: decoder) {")
                     indent {
                         print("self = .\(dc.enumCase)(obj)")
                     }
                     print("} else ", terminator: "")
                 }
                 block {
-                    block("enum DiscriminatorKeys: String, CodingKey") {
-                        print(#"case type = "\#(discriminator.propertyName)""#)
-                    }
-                    print("let container = try decoder.container(keyedBy: DiscriminatorKeys.self)")
-                    print("let type = try container.decode(String.self, forKey: .type)")
                     print(#"throw DecodingError.typeMismatch(\#(modelName).self, DecodingError.Context(codingPath: decoder.codingPath, debugDescription: "unexpected subclass type \(type)"))"#)
                 }
             }

diff --git a/Tests/InheritanceTest1.swift b/Tests/InheritanceTest1.swift
@@ -59,17 +59,19 @@ final class InheritanceTest1: XCTestCase {
         case cat(Cat)
         case dog(Dog)
 
+        enum DiscriminatorKeys: String, CodingKey {
+            case type = "status"
+        }
+
         public init(from decoder: Decoder) throws {
-            if let obj = try? Cat(from: decoder), obj.status == .cat {
+            let container = try decoder.container(keyedBy: DiscriminatorKeys.self)
+            let type = try container.decode(AnimalType.self, forKey: .type)
+
+            if type == .cat, let obj = try? Cat(from: decoder) {
                 self = .cat(obj)
-            } else if let obj = try? Dog(from: decoder), obj.status == .dog {
+            } else if type == .dog, let obj = try? Dog(from: decoder) {
                 self = .dog(obj)
             } else {
-                enum DiscriminatorKeys: String, CodingKey {
-                    case type = "status"
-                }
-                let container = try decoder.container(keyedBy: DiscriminatorKeys.self)
-                let type = try container.decode(String.self, forKey: .type)
                 throw DecodingError.typeMismatch(Animal.self, DecodingError.Context(codingPath: decoder.codingPath, debugDescription: "unexpected subclass type \(type)"))
             }
         }

diff --git a/Tests/InheritanceTest2.swift b/Tests/InheritanceTest2.swift
@@ -70,19 +70,21 @@ final class InheritanceTest2: XCTestCase {
         case dog(Dog)
         case animal(AnimalBase)
 
+        enum DiscriminatorKeys: String, CodingKey {
+            case type = "status"
+        }
+
         public init(from decoder: Decoder) throws {
-            if let obj = try? Cat(from: decoder), obj.status == "cat" {
+            let container = try decoder.container(keyedBy: DiscriminatorKeys.self)
+            let type = try container.decode(String.self, forKey: .type)
+
+            if type == "cat", let obj = try? Cat(from: decoder) {
                 self = .cat(obj)
-            } else if let obj = try? Dog(from: decoder), obj.status == "dog" {
+            } else if type == "dog", let obj = try? Dog(from: decoder) {
                 self = .dog(obj)
-            } else if let obj = try? AnimalBase(from: decoder), obj.status == "Animal" {
+            } else if type == "Animal", let obj = try? AnimalBase(from: decoder) {
                 self = .animal(obj)
             } else {
-                enum DiscriminatorKeys: String, CodingKey {
-                    case type = "status"
-                }
-                let container = try decoder.container(keyedBy: DiscriminatorKeys.self)
-                let type = try container.decode(String.self, forKey: .type)
                 throw DecodingError.typeMismatch(Animal.self, DecodingError.Context(codingPath: decoder.codingPath, debugDescription: "unexpected subclass type \(type)"))
             }
         }