Added generation of typed helpers when using nested_flatbuffers in Java/C#. Fixes #3500

src/idl_gen_general.cpp

@@ -876,7 +876,27 @@ static void GenStruct(const LanguageParameters &lang, const Parser &parser,
           break;
       }
     }
-
+	// generate object accessors if is nested_flatbuffer
+	auto nested = field.attributes.Lookup("nested_flatbuffer");
+	if (nested) {
+		auto nested_qualified_name =
+			parser.namespaces_.back()->GetFullyQualifiedName(nested->constant);
+		auto nested_type = parser.structs_.Lookup(nested_qualified_name);
+		auto nested_type_name = WrapInNameSpace(parser, *nested_type);
+		auto nestedMethodName = MakeCamel(field.name, lang.first_camel_upper) 
+			+ "As" + nested_type_name;
+		auto getNestedMethodName = nestedMethodName;
+		if (lang.language == IDLOptions::kCSharp) {
+			getNestedMethodName = "Get" + nestedMethodName;
+		}
+		code += "  public " + nested_type_name + " ";
+		code += nestedMethodName + "() { return ";
+		code += getNestedMethodName + "(new " + nested_type_name + "()); }\n";
+		code += "  public " + nested_type_name + " " + getNestedMethodName;
+		code += "(" + nested_type_name + " obj) { ";
+		code += "int o = __offset(" + NumToString(field.value.offset) +"); ";
+		code += "return o != 0 ? obj.__init(__indirect(__vector(o)), bb) : null; }\n";
+	}
     // generate mutators for scalar fields or vectors of scalars
     if (parser.opts.mutable_buffer) {
       auto underlying_type = field.value.type.base_type == BASE_TYPE_VECTOR

tests/FlatBuffers.Test/FlatBuffersExampleTests.cs

@@ -215,5 +215,44 @@ namespace FlatBuffers.Test
             Assert.AreEqual("NONE", Any.NONE.ToString());
             Assert.AreEqual("Monster", Any.Monster.ToString());
         }
+
+        [FlatBuffersTestMethod]
+        public void TestNestedFlatBuffer()
+        {
+            const string nestedMonsterName = "NestedMonsterName";
+            const short nestedMonsterHp = 600;
+            const short nestedMonsterMana = 1024;
+            // Create nested buffer as a Monster type
+            var fbb1 = new FlatBufferBuilder(16);
+            var str1 = fbb1.CreateString(nestedMonsterName);
+            Monster.StartMonster(fbb1);
+            Monster.AddName(fbb1, str1);
+            Monster.AddHp(fbb1, nestedMonsterHp);
+            Monster.AddMana(fbb1, nestedMonsterMana);
+            var monster1 = Monster.EndMonster(fbb1);
+            Monster.FinishMonsterBuffer(fbb1, monster1);
+            var fbb1Bytes = fbb1.SizedByteArray();
+            fbb1 = null;
+
+            // Create a Monster which has the first buffer as a nested buffer
+            var fbb2 = new FlatBufferBuilder(16);
+            var str2 = fbb2.CreateString("My Monster");
+            var nestedBuffer = Monster.CreateTestnestedflatbufferVector(fbb2, fbb1Bytes);
+            Monster.StartMonster(fbb2);
+            Monster.AddName(fbb2, str2);
+            Monster.AddHp(fbb2, 50);
+            Monster.AddMana(fbb2, 32);
+            Monster.AddTestnestedflatbuffer(fbb2, nestedBuffer);
+            var monster = Monster.EndMonster(fbb2);
+            Monster.FinishMonsterBuffer(fbb2, monster);
+            
+            // Now test the data extracted from the nested buffer
+            var mons = Monster.GetRootAsMonster(fbb2.DataBuffer);
+            var nestedMonster = mons.TestnestedflatbufferAsMonster();
+
+            Assert.AreEqual(nestedMonsterMana, nestedMonster.Mana);
+            Assert.AreEqual(nestedMonsterHp, nestedMonster.Hp);
+            Assert.AreEqual(nestedMonsterName, nestedMonster.Name);
+        }
     }
 }

tests/JavaTest.java

@@ -159,6 +159,8 @@ class JavaTest {
 
         TestNamespaceNesting();
 
+        TestNestedFlatBuffer();
+
         System.out.println("FlatBuffers test: completed successfully");
     }
 
@@ -242,6 +244,42 @@ class JavaTest {
         TableInFirstNS.addFooTable(fbb, nestedTableOff);
         int off = TableInFirstNS.endTableInFirstNS(fbb);
     }
+    
+    static void TestNestedFlatBuffer() {
+        final String nestedMonsterName = "NestedMonsterName";
+        final short nestedMonsterHp = 600;
+        final short nestedMonsterMana = 1024;
+        
+        FlatBufferBuilder fbb1 = new FlatBufferBuilder(16);
+        int str1 = fbb1.createString(nestedMonsterName);
+        Monster.startMonster(fbb1);
+        Monster.addName(fbb1, str1);
+        Monster.addHp(fbb1, nestedMonsterHp);
+        Monster.addMana(fbb1, nestedMonsterMana);
+        int monster1 = Monster.endMonster(fbb1);
+        Monster.finishMonsterBuffer(fbb1, monster1);
+        byte[] fbb1Bytes = fbb1.sizedByteArray();
+        fbb1 = null;
+        
+        FlatBufferBuilder fbb2 = new FlatBufferBuilder(16);        
+        int str2 = fbb2.createString("My Monster");
+        int nestedBuffer = Monster.createTestnestedflatbufferVector(fbb2, fbb1Bytes);
+        Monster.startMonster(fbb2);
+        Monster.addName(fbb2, str2);
+        Monster.addHp(fbb2, (short)50);
+        Monster.addMana(fbb2, (short)32);
+        Monster.addTestnestedflatbuffer(fbb2, nestedBuffer);
+        int monster = Monster.endMonster(fbb2);
+        Monster.finishMonsterBuffer(fbb2, monster);
+        
+        // Now test the data extracted from the nested buffer
+        Monster mons = Monster.getRootAsMonster(fbb2.dataBuffer());
+        Monster nestedMonster = mons.testnestedflatbufferAsMonster();
+
+        TestEq(nestedMonsterMana, nestedMonster.mana());
+        TestEq(nestedMonsterHp, nestedMonster.hp());
+        TestEq(nestedMonsterName, nestedMonster.name());
+    }
 
     static <T> void TestEq(T a, T b) {
         if (!a.equals(b)) {

tests/MyGame/Example/Monster.cs

@@ -45,6 +45,8 @@ public sealed class Monster : Table {
   public byte GetTestnestedflatbuffer(int j) { int o = __offset(30); return o != 0 ? bb.Get(__vector(o) + j * 1) : (byte)0; }
   public int TestnestedflatbufferLength { get { int o = __offset(30); return o != 0 ? __vector_len(o) : 0; } }
   public ArraySegment<byte>? GetTestnestedflatbufferBytes() { return __vector_as_arraysegment(30); }
+  public Monster TestnestedflatbufferAsMonster() { return GetTestnestedflatbufferAsMonster(new Monster()); }
+  public Monster GetTestnestedflatbufferAsMonster(Monster obj) { int o = __offset(30); return o != 0 ? obj.__init(__indirect(__vector(o)), bb) : null; }
   public bool MutateTestnestedflatbuffer(int j, byte testnestedflatbuffer) { int o = __offset(30); if (o != 0) { bb.Put(__vector(o) + j * 1, testnestedflatbuffer); return true; } else { return false; } }
   public Stat Testempty { get { return GetTestempty(new Stat()); } }
   public Stat GetTestempty(Stat obj) { int o = __offset(32); return o != 0 ? obj.__init(__indirect(o + bb_pos), bb) : null; }

tests/MyGame/Example/Monster.java

@@ -51,6 +51,8 @@ public final class Monster extends Table {
   public int testnestedflatbuffer(int j) { int o = __offset(30); return o != 0 ? bb.get(__vector(o) + j * 1) & 0xFF : 0; }
   public int testnestedflatbufferLength() { int o = __offset(30); return o != 0 ? __vector_len(o) : 0; }
   public ByteBuffer testnestedflatbufferAsByteBuffer() { return __vector_as_bytebuffer(30, 1); }
+  public Monster testnestedflatbufferAsMonster() { return testnestedflatbufferAsMonster(new Monster()); }
+  public Monster testnestedflatbufferAsMonster(Monster obj) { int o = __offset(30); return o != 0 ? obj.__init(__indirect(__vector(o)), bb) : null; }
   public boolean mutateTestnestedflatbuffer(int j, int testnestedflatbuffer) { int o = __offset(30); if (o != 0) { bb.put(__vector(o) + j * 1, (byte)testnestedflatbuffer); return true; } else { return false; } }
   public Stat testempty() { return testempty(new Stat()); }
   public Stat testempty(Stat obj) { int o = __offset(32); return o != 0 ? obj.__init(__indirect(o + bb_pos), bb) : null; }