Update the books

docs/en/src/define_interface.md

@@ -1,8 +1,8 @@
 # Interface
 
-`Interface` is used to abstract `Object`s with common fields. 
-`Async-graphql` implemented it as a wrapper. 
-The wrapper will forward Resolve to the `Object` that implemented this `Interface`. 
+`Interface` is used to abstract `Object`s with common fields.
+`Async-graphql` implemented it as a wrapper.
+The wrapper will forward Resolve to the `Object` that implemented this `Interface`.
 Therefore, the `Object`'s fields' type, arguments must match with the `Interface`'s.
 
 `Async-graphql` implemented auto conversion from `Object` to `Interface`, you only need to call `Into::into`.
@@ -44,5 +44,8 @@ impl Square {
     field(name = "area", type = "f32"),
     field(name = "scale", type = "Shape", arg(name = "s", type = "f32"))
 )]
-struct Shape(Circle, Square);
-```
+enum Shape {
+    Circle(Circle),
+    Square(Square),
+}
+```

docs/en/src/define_union.md

@@ -1,7 +1,7 @@
 # Union
 
 The definition of `Union` is similar to `Interface`'s, **but no field allowed.**.
-The implemention is quite similar for `Async-graphql`. 
+The implemention is quite similar for `Async-graphql`.
 From `Async-graphql`'s perspective, `Union` is a subset of `Interface`.
 
 The following example modified the definition of `Interface` a little bit and removed fields.
@@ -40,5 +40,8 @@ impl Square {
 }
 
 #[Union]
-struct Shape(Circle, Square);
-```
+enum Shape {
+    Circle(Circle),
+    Square(Square),
+}
+```

docs/zh-CN/src/define_interface.md

@@ -41,5 +41,8 @@ impl Square {
     field(name = "area", type = "f32"),
     field(name = "scale", type = "Shape", arg(name = "s", type = "f32"))
 )]
-struct Shape(Circle, Square);
-```
+enum Shape {
+    Circle(Circle),
+    Square(Square),
+}
+```

docs/zh-CN/src/define_union.md

@@ -38,5 +38,8 @@ impl Square {
 }
 
 #[Union]
-struct Shape(Circle, Square);
-```
+enum Shape {
+    Circle(Circle),
+    Square(Square),
+}
+```