Add Element.StructField()

This new method returns reflect.StructField if element represents a field of a struct. It can be used for writing callbacks reading field tags for example.

Author: elgopher

mapify.go

@@ -31,14 +31,26 @@ type MapValue func(path string, e Element) (interface{}, error)
 
 // Element represents either a map entry, field of a struct or unnamed element of a slice.
 type Element struct {
-	name string
+	name  string
+	field *reflect.StructField
 	reflect.Value
 }
 
+// Name returns field name of a struct, key of a map or empty string, when it represents element of a slice.
 func (e Element) Name() string {
 	return e.name
 }
 
+// StructField returns the reflect.StructField if e represents a field of a struct. If not, ok is false.
+func (e Element) StructField() (_ reflect.StructField, ok bool) {
+	if e.field == nil {
+		return reflect.StructField{}, false
+	}
+
+	return *e.field, true
+}
+
+// MapAny maps any object (struct, map, slice etc.) by converting each struct found to a map.
 func (i Mapper) MapAny(v interface{}) (interface{}, error) {
 	return i.newInstance().mapAny("", v)
 }
@@ -89,7 +101,7 @@ func (i Mapper) mapStruct(path string, reflectValue reflect.Value) (map[string]i
 		fieldName := field.Name
 		fieldPath := path + "." + fieldName
 		value := reflectValue.Field(j)
-		element := Element{name: fieldName, Value: value}
+		element := Element{name: fieldName, Value: value, field: &field}
 
 		if err := i.mapStructField(fieldPath, element, result); err != nil {
 			return nil, err

mapify_test.go

@@ -526,3 +526,34 @@ type stringError string
 func (d stringError) Error() string {
 	return string(d)
 }
+
+func TestElement_StructField(t *testing.T) {
+	t.Run("should return struct field in callbacks", func(t *testing.T) {
+		mapper := mapify.Mapper{
+			Filter: func(path string, e mapify.Element) (bool, error) {
+				assertStructField(t, "Field", e)
+
+				return true, nil
+			},
+			Rename: func(path string, e mapify.Element) (string, error) {
+				assertStructField(t, "Field", e)
+
+				return e.Name(), nil
+			},
+			MapValue: func(path string, e mapify.Element) (interface{}, error) {
+				assertStructField(t, "Field", e)
+
+				return e.Interface(), nil
+			},
+		}
+		_, _ = mapper.MapAny(struct{ Field string }{})
+	})
+}
+
+func assertStructField(t *testing.T, fieldName string, e mapify.Element) {
+	t.Helper()
+
+	field, ok := e.StructField()
+	require.True(t, ok)
+	assert.Equal(t, fieldName, field.Name)
+}