Add 'TimeStamp' struct for embed

README.md

@@ -447,6 +447,18 @@ type User struct {
 
 Update/Insert/Delete hooks of an embedded struct will be called before the hooks of the child struct.
 
+Also Genmai has defined `TimeStamp` struct for commonly used fields.
+
+```
+type User struct {
+    Id int64
+
+    genmai.TimeStamp
+}
+```
+
+See the Godoc of [TimeStamp](http://godoc.org/github.com/naoina/genmai#TimeStamp) for more information.
+
 ## Documentation
 
 API document and more examples are available here:

field.go

@@ -0,0 +1,28 @@
+package genmai
+
+import "time"
+
+// TimeStamp is fields for timestamps that commonly used.
+type TimeStamp struct {
+	// Time of creation. This field will be set automatically by BeforeInsert.
+	CreatedAt time.Time
+
+	// Time of update. This field will be set by BeforeInsert or BeforeUpdate.
+	UpdatedAt time.Time
+}
+
+// BeforeInsert sets current time to CreatedAt and UpdatedAt field.
+// It always returns nil.
+func (ts *TimeStamp) BeforeInsert() error {
+	n := now()
+	ts.CreatedAt = n
+	ts.UpdatedAt = n
+	return nil
+}
+
+// BeforeUpdate sets current time to UpdatedAt field.
+// It always returns nil.
+func (ts *TimeStamp) BeforeUpdate() error {
+	ts.UpdatedAt = now()
+	return nil
+}

field_test.go

@@ -0,0 +1,85 @@
+package genmai
+
+import (
+	"reflect"
+	"testing"
+	"time"
+)
+
+func TestTimeStamp_BeforeInsert(t *testing.T) {
+	createdAt, err := time.Parse("2006-01-02 15:04:05", "2014-02-24 22:36:56")
+	if err != nil {
+		t.Fatal(err)
+	}
+	updatedAt, err := time.Parse("2006-01-02 15:04:05", "2014-02-24 23:51:26")
+	if err != nil {
+		t.Fatal(err)
+	}
+	n, err := time.Parse("2006-01-02 15:04:05", "2000-02-02 16:57:38")
+	if err != nil {
+		t.Fatal(err)
+	}
+	baknow := now
+	now = func() time.Time {
+		return n
+	}
+	defer func() {
+		now = baknow
+	}()
+	tm := &TimeStamp{
+		CreatedAt: createdAt,
+		UpdatedAt: updatedAt,
+	}
+	if err := tm.BeforeInsert(); err != nil {
+		t.Fatal(err)
+	}
+	actual := tm.CreatedAt
+	expected := n
+	if !reflect.DeepEqual(actual, expected) {
+		t.Errorf("Expect %q, but %q", expected, actual)
+	}
+	actual = tm.UpdatedAt
+	expected = n
+	if !reflect.DeepEqual(actual, expected) {
+		t.Errorf("Expect %q, but %q", expected, actual)
+	}
+}
+
+func TestTimeStamp_BeforeUpdate(t *testing.T) {
+	createdAt, err := time.Parse("2006-01-02 15:04:05", "2014-02-24 22:36:56")
+	if err != nil {
+		t.Fatal(err)
+	}
+	updatedAt, err := time.Parse("2006-01-02 15:04:05", "2014-02-24 23:51:26")
+	if err != nil {
+		t.Fatal(err)
+	}
+	n, err := time.Parse("2006-01-02 15:04:05", "2000-02-02 16:57:38")
+	if err != nil {
+		t.Fatal(err)
+	}
+	baknow := now
+	now = func() time.Time {
+		return n
+	}
+	defer func() {
+		now = baknow
+	}()
+	tm := &TimeStamp{
+		CreatedAt: createdAt,
+		UpdatedAt: updatedAt,
+	}
+	if err := tm.BeforeUpdate(); err != nil {
+		t.Fatal(err)
+	}
+	actual := tm.CreatedAt
+	expected := createdAt
+	if !reflect.DeepEqual(actual, expected) {
+		t.Errorf("Expect %q, but %q", expected, actual)
+	}
+	actual = tm.UpdatedAt
+	expected = n
+	if !reflect.DeepEqual(actual, expected) {
+		t.Errorf("Expect %q, but %q", expected, actual)
+	}
+}