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docs/by-example/36-reflection.md

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+---
+title: Type reflection
+id: type-reflection
+slug: /type-reflection
+sidebar_label: Type reflection
+description: Type reflection
+keywords: [Wing language, Type reflection]
+image: /img/wing-by-example.png
+---
+
+The `@type` intrinsic function returns a reflection of the type passed to it.
+
+You can access its `.kind` property to get the kind of the type, and use various helper methods like `.asStruct()`, `.asClass()`, `.asInterface()`, etc. to access related properties.
+
+```js playground example title="main.w"
+let generateJsonSchema = (structType: std.reflect.Type): str => {
+  if let st = structType.asStruct() {
+    let schema = MutJson {
+      type: "object",
+      properties: {},
+      required: []
+    };
+
+    for name in st.fields.keys() {
+      let fieldSchema = MutJson {};
+      let var field = st.fields[name].child;
+      let var required = true;
+      if let opt = field.asOptional() {
+        required = false;
+        field = opt.child;
+      }
+
+      if field.kind == "str" {
+        fieldSchema["type"] = "string";
+      } else if field.kind == "num" {
+        fieldSchema["type"] = "number";
+      } // ...handle other types
+
+      schema["properties"][name] = fieldSchema;
+      if required {
+        // TODO: https://github.com/winglang/wing/issues/6929
+        unsafeCast(schema["required"])?.push(name);
+      }
+    }
+
+    return Json.stringify(schema);
+  }
+
+  throw "input must be a struct type";
+};
+
+struct User {
+  name: str;
+  age: num;
+  email: str?;
+}
+
+log(generateJsonSchema(@type(User)));
+```
+
+```bash title="Wing console output"
+# Run locally with wing console
+{"type":"object","properties":{"age":{"type":"number"},"email":{"type":"string"},"name":{"type":"string"}},"required":["age","name"]}
+```
+
+