adding function file

clause/function.go

@@ -0,0 +1,42 @@
+package clause
+
+import (
+	"fmt"
+	"log"
+)
+
+type Database string
+
+var (
+	Postgres Database = "postgres"
+	Sqlite   Database = "sqlite"
+)
+
+type Function interface {
+	GetSql() string
+}
+
+type FuncDateWithoutTime struct {
+	Database Database
+	Field    string
+	Alias    string
+	SQL      string
+}
+
+func (fnc FuncDateWithoutTime) GetSql() string {
+	alias := fnc.Alias
+	if fnc.Alias == "" {
+		alias = fnc.Field
+	}
+	switch fnc.Database {
+	case Postgres:
+		fnc.SQL = fmt.Sprintf(" to_char(%s, %s) as %s", fnc.Field, "'YYYY-MM-DD'", alias)
+	case Sqlite:
+		fnc.SQL = fmt.Sprintf(" strftime(%s, %s) as %s", "'%Y-%m-%d' ", fnc.Field, alias)
+	default:
+		log.Print("database not implemented yet for this function")
+		return ""
+	}
+
+	return fnc.SQL
+}

tests/query_test.go

@@ -1359,3 +1359,32 @@ func TestQueryResetNullValue(t *testing.T) {
 	AssertEqual(t, q1, qs[0])
 	AssertEqual(t, q2, qs[1])
 }
+
+func TestFuncDateWihtoutTimeSQLITE(t *testing.T) {
+	users := []User{
+		*GetUser("find", Config{}),
+		*GetUser("find", Config{}),
+		*GetUser("find", Config{}),
+	}
+
+	if err := DB.Create(&users).Error; err != nil {
+		t.Fatalf("errors happened when create users: %v", err)
+	}
+
+	t.Run("First with Function", func(t *testing.T) {
+		var first struct {
+			Birthday string
+			Name     string
+		}
+		var fn clause.FuncDateWithoutTime = clause.FuncDateWithoutTime{Database: "sqlite", Field: "birthday"}
+		var sql string = fn.GetSql()
+		if err := DB.Model(&User{}).Select([]string{sql, "name"}).Where("name = ?", "find").First(&first).Error; err != nil {
+			t.Errorf("errors happened when query first: %v", err)
+		} else {
+			now := time.Now().Format("2006-01-02")
+			AssertEqual(t, &first.Birthday, now)
+			AssertEqual(t, &first.Name, "find")
+
+		}
+	})
+}