Add Last Method, And update README for method First, Find

README.md

@@ -118,11 +118,23 @@ db.Save(&user)
 ```go
 // Get the first record
 db.First(&user)
-//// SELECT * FROM users LIMIT 1;
+//// SELECT * FROM users ORDER BY id LIMIT 1;
 // Search table `users` are guessed from the out struct type.
 // You are possible to specify the table name with Model() if no out struct for some methods like Pluck()
 // Or set table name with Table(), if so, it will ignore the out struct even have it. more details following.
 
+// Get the last record
+db.Last(&user)
+//// SELECT * FROM users ORDER BY id DESC LIMIT 1;
+
+// Get a record without order by primary key
+db.Find(&user)
+//// SELECT * FROM users LIMIT 1;
+
+// Get first record as map
+db.First(&users)
+//// SELECT * FROM users LIMIT 1;
+
 // Get All records
 db.Find(&users)
 //// SELECT * FROM users;

chain.go

@@ -175,9 +175,12 @@ func (s *Chain) Exec(sql string) *Chain {
 }
 
 func (s *Chain) First(out interface{}, where ...interface{}) *Chain {
-	do := s.do(out)
-	do.limitStr = "1"
-	do.where(where...).query()
+	s.do(out).where(where...).first()
+	return s
+}
+
+func (s *Chain) Last(out interface{}, where ...interface{}) *Chain {
+	s.do(out).where(where...).last()
 	return s
 }
 

do.go

@@ -287,6 +287,18 @@ func (s *Do) prepareQuerySql() {
 	return
 }
 
+func (s *Do) first() {
+	s.limitStr = "1"
+	s.orderStrs = append(s.orderStrs, s.model.primaryKeyDb())
+	s.query()
+}
+
+func (s *Do) last() {
+	s.limitStr = "1"
+	s.orderStrs = append(s.orderStrs, s.model.primaryKeyDb()+" DESC")
+	s.query()
+}
+
 func (s *Do) query() {
 	var (
 		is_slice  bool
@@ -297,6 +309,8 @@ func (s *Do) query() {
 	if dest_out.Kind() == reflect.Slice {
 		is_slice = true
 		dest_type = dest_out.Type().Elem()
+	} else {
+		s.limitStr = "1"
 	}
 
 	s.prepareQuerySql()

gorm_test.go

@@ -117,6 +117,23 @@ func TestSaveAndFind(t *testing.T) {
 	db.Find(&users)
 }
 
+func TestFirstAndLast(t *testing.T) {
+	var user1, user2, user3, user4 User
+	db.First(&user1)
+	db.Order("id").Find(&user2)
+	db.Last(&user3)
+	db.Order("id desc").Find(&user4)
+	if user1.Id != user2.Id || user3.Id != user4.Id {
+		t.Errorf("First and Last should works correctly")
+	}
+
+	var users []User
+	db.First(&users)
+	if len(users) != 1 {
+		t.Errorf("Find first record as map")
+	}
+}
+
 func TestSaveAndUpdate(t *testing.T) {
 	name, name2, new_name := "update", "update2", "new_update"
 	user := User{Name: name, Age: 1}

main.go

@@ -34,6 +34,10 @@ func (s *DB) First(out interface{}, where ...interface{}) *Chain {
 	return s.buildChain().First(out, where...)
 }
 
+func (s *DB) Last(out interface{}, where ...interface{}) *Chain {
+	return s.buildChain().Last(out, where...)
+}
+
 func (s *DB) Attrs(attrs ...interface{}) *Chain {
 	return s.buildChain().Attrs(attrs...)
 }