Fix set value on nested field

field.go

@@ -117,7 +117,16 @@ func (f *Field) Field(name string) *Field {
 // FieldOk returns the field from a nested struct. The boolean returns whether
 // the field was found (true) or not (false).
 func (f *Field) FieldOk(name string) (*Field, bool) {
-	v := strctVal(f.value.Interface())
+	value := &f.value
+	// value must be settable so we need to make sure it holds the address of the
+	// variable and not a copy, so we can pass the pointer to strctVal instead of a
+	// copy (which is not assigned to any variable, hence not settable).
+	// see "https://blog.golang.org/laws-of-reflection#TOC_8."
+	if f.value.Kind() != reflect.Ptr {
+		a := f.value.Addr()
+		value = &a
+	}
+	v := strctVal(value.Interface())
 	t := v.Type()
 
 	field, ok := t.FieldByName(name)

structs_test.go

@@ -1022,6 +1022,28 @@ func TestNestedNilPointer(t *testing.T) {
 	_ = Map(personWithDogWithCollar) // Doesn't panic
 }
 
+func TestSetValueOnNestedField(t *testing.T) {
+	type Base struct {
+		ID int
+	}
+
+	type User struct {
+		Base
+		Name string
+	}
+
+	u := User{}
+	s := New(&u)
+	f := s.Field("Base").Field("ID")
+	err := f.Set(10)
+	if err != nil {
+		t.Errorf("Error %v", err)
+	}
+	if f.Value().(int) != 10 {
+		t.Errorf("Value should be equal to 10, got %v", f.Value())
+	}
+}
+
 type Person struct {
 	Name string
 	Age  int