Merge pull request #5820 from heshanpadmasiri/feat/distinct-object

Update distinct object examples

examples/distinct-object-types/distinct_object_types.bal

@@ -1,30 +1,58 @@
 import ballerina/io;
 
-// The `Person` object type that contains a string field called `name`.
-type Person distinct object {
+class Person {
     public string name;
+
+    function init(string name) {
+        self.name = name;
+    }
 };
 
-// The `Engineer` and `Manager` classes are structurally the same but introducing the
-// `distinct` keyword distinguishes them by considering them as nominal types.
-distinct class Engineer {
-    *Person;
+// The `DistinctPerson` type is a proper subtype of the `Person` type.
+distinct class DistinctPerson {
+    public string name;
+
+    function init(string name) {
+        self.name = name;
+    }
+}
+
+// The `SomeWhatDistinctPerson` type is a subtype of the `DistinctPerson` type
+// since it includes the `DistinctPerson` type's type IDs via inclusion.
+class SomeWhatDistinctPerson {
+    *DistinctPerson;
+
+    public string name;
 
     function init(string name) {
         self.name = name;
     }
 }
 
-distinct class Manager {
-    *Person;
+// The `EvenMoreDistinctPerson` type is a proper subtype of the `DistinctPerson` 
+// type since it has an additional type ID.
+distinct class EvenMoreDistinctPerson {
+    *DistinctPerson;
+
+    public string name;
 
     function init(string name) {
         self.name = name;
     }
 }
 
 public function main() {
-    Person person = new Engineer("Alice");
-    // The `is` operator can be used to distinguish distinct subtypes.
-    io:println(person is Engineer ? "Engineer" : "Manager");
+    Person person = new ("John Smith");
+    io:println(person is DistinctPerson);
+
+    DistinctPerson distinctPerson = new ("Alice Johnson");
+    io:println(distinctPerson is Person);
+
+    SomeWhatDistinctPerson someWhatDistinctPerson = new ("Michael Brown");
+    io:println(someWhatDistinctPerson is DistinctPerson);
+    io:println(distinctPerson is SomeWhatDistinctPerson);
+
+    EvenMoreDistinctPerson evenMoreDistinctPerson = new ("Sarah Wilson");
+    io:println(evenMoreDistinctPerson is DistinctPerson);
+    io:println(distinctPerson is EvenMoreDistinctPerson);
 }

examples/distinct-object-types/distinct_object_types.md

@@ -1,8 +1,8 @@
 # Distinct object types
 
-Using the `distinct` keyword in the type definition creates distinct object types. This concept allows defining a type with nominal typing within a structured type system. This is useful when interacting with the external world through API interfaces like `GraphQL`. You may want to leverage nominal typing via this distinct typing feature of Ballerina.
+For more explicit control over object type relations you can use `distinct` object types. Each distinct object type declaration has a unique type ID. When you include a distinct object type within another object type declaration, the new type's type ID set will include the type IDs of the included type. When checking if a given object type `OSub` is a subtype of a distinct object type `OSuper` there is the additional requirement that the `OSub` type must contain all the type IDs of the `OSuper` type.
 
-Conceptually, a distinct type including another distinct type results in multiple interface inheritance.
+This way you can achieve the same behavior as a nominal type system within Ballerina's structured type system, which is useful to support features such as GraphQL API interfaces.
 
 ::: code distinct_object_types.bal :::
 
@@ -13,3 +13,4 @@ Conceptually, a distinct type including another distinct type results in multipl
 - [Error subtyping](/learn/by-example/error-subtyping/)
 - [Defining classes](/learn/by-example/defining-classes/)
 - [Flexibly typed](https://ballerina.io/why-ballerina/flexibly-typed/)
+- [GraphQL service - Interfaces](https://ballerina.io/learn/by-example/graphql-interfaces/)

examples/distinct-object-types/distinct_object_types.out

@@ -1,2 +1,7 @@
 $ bal distinct_object_types.bal
-Engineer
+false
+true
+true
+true
+true
+false