聊聊gorm的Model

序

本文主要研究一下gorm的Model

Model

gorm.io/gorm@v1.20.10/model.go

// Model a basic GoLang struct which includes the following fields: ID, CreatedAt, UpdatedAt, DeletedAt
// It may be embedded into your model or you may build your own model without it
//    type User struct {
//      gorm.Model
//    }
type Model struct {
	ID        uint `gorm:"primarykey"`
	CreatedAt time.Time
	UpdatedAt time.Time
	DeletedAt DeletedAt `gorm:"index"`
}

Model定义了ID、CreatedAt、UpdatedAt、DeletedAt属性

ParseField

gorm.io/gorm@v1.20.10/schema/field.go

func (schema *Schema) ParseField(fieldStruct reflect.StructField) *Field {
	var err error

	field := &Field{
		Name:                   fieldStruct.Name,
		BindNames:              []string{fieldStruct.Name},
		FieldType:              fieldStruct.Type,
		IndirectFieldType:      fieldStruct.Type,
		StructField:            fieldStruct,
		Creatable:              true,
		Updatable:              true,
		Readable:               true,
		Tag:                    fieldStruct.Tag,
		TagSettings:            ParseTagSetting(fieldStruct.Tag.Get("gorm"), ";"),
		Schema:                 schema,
		AutoIncrementIncrement: 1,
	}

	for field.IndirectFieldType.Kind() == reflect.Ptr {
		field.IndirectFieldType = field.IndirectFieldType.Elem()
	}

	fieldValue := reflect.New(field.IndirectFieldType)
	// if field is valuer, used its value or first fields as data type
	valuer, isValuer := fieldValue.Interface().(driver.Valuer)
	
	//......

	field.GORMDataType = field.DataType

	if dataTyper, ok := fieldValue.Interface().(GormDataTypeInterface); ok {
		field.DataType = DataType(dataTyper.GormDataType())
	}

	if v, ok := field.TagSettings["AUTOCREATETIME"]; ok || (field.Name == "CreatedAt" && (field.DataType == Time || field.DataType == Int || field.DataType == Uint)) {
		if strings.ToUpper(v) == "NANO" {
			field.AutoCreateTime = UnixNanosecond
		} else if strings.ToUpper(v) == "MILLI" {
			field.AutoCreateTime = UnixMillisecond
		} else {
			field.AutoCreateTime = UnixSecond
		}
	}

	if v, ok := field.TagSettings["AUTOUPDATETIME"]; ok || (field.Name == "UpdatedAt" && (field.DataType == Time || field.DataType == Int || field.DataType == Uint)) {
		if strings.ToUpper(v) == "NANO" {
			field.AutoUpdateTime = UnixNanosecond
		} else if strings.ToUpper(v) == "MILLI" {
			field.AutoUpdateTime = UnixMillisecond
		} else {
			field.AutoUpdateTime = UnixSecond
		}
	}

	//......

	return field
}

ParseField方法会解析field的属性，如果field的name为CreatedAt或者UpdatedAt，且dataType为Time、Int、Unit或者tag标注了AUTOCREATETIME或者AUTOUPDATETIME，则会设置field.AutoCreateTime或者field.AutoUpdateTime

TimeType

gorm.io/gorm@v1.20.10/schema/field.go

type TimeType int64

const (
	UnixSecond      TimeType = 1
	UnixMillisecond TimeType = 2
	UnixNanosecond  TimeType = 3
)

field.AutoCreateTime、AutoUpdateTime属性为TimeType类型，该类型有UnixSecond、UnixMillisecond、UnixNanosecond三种类型

ConvertToCreateValues

gorm.io/gorm@v1.20.10/callbacks/create.go

// ConvertToCreateValues convert to create values
func ConvertToCreateValues(stmt *gorm.Statement) (values clause.Values) {
	switch value := stmt.Dest.(type) {
	case map[string]interface{}:
		values = ConvertMapToValuesForCreate(stmt, value)
	case *map[string]interface{}:
		values = ConvertMapToValuesForCreate(stmt, *value)
	case []map[string]interface{}:
		values = ConvertSliceOfMapToValuesForCreate(stmt, value)
	case *[]map[string]interface{}:
		values = ConvertSliceOfMapToValuesForCreate(stmt, *value)
	default:
		var (
			selectColumns, restricted = stmt.SelectAndOmitColumns(true, false)
			curTime                   = stmt.DB.NowFunc()
			isZero                    bool
		)
		values = clause.Values{Columns: make([]clause.Column, 0, len(stmt.Schema.DBNames))}

		for _, db := range stmt.Schema.DBNames {
			if field := stmt.Schema.FieldsByDBName[db]; !field.HasDefaultValue || field.DefaultValueInterface != nil {
				if v, ok := selectColumns[db]; (ok && v) || (!ok && (!restricted || field.AutoCreateTime > 0 || field.AutoUpdateTime > 0)) {
					values.Columns = append(values.Columns, clause.Column{Name: db})
				}
			}
		}

		switch stmt.ReflectValue.Kind() {
		case reflect.Slice, reflect.Array:
			stmt.SQL.Grow(stmt.ReflectValue.Len() * 18)
			values.Values = make([][]interface{}, stmt.ReflectValue.Len())
			defaultValueFieldsHavingValue := map[*schema.Field][]interface{}{}
			if stmt.ReflectValue.Len() == 0 {
				stmt.AddError(gorm.ErrEmptySlice)
				return
			}

			for i := 0; i < stmt.ReflectValue.Len(); i++ {
				rv := reflect.Indirect(stmt.ReflectValue.Index(i))
				if !rv.IsValid() {
					stmt.AddError(fmt.Errorf("slice data #%v is invalid: %w", i, gorm.ErrInvalidData))
					return
				}

				values.Values[i] = make([]interface{}, len(values.Columns))
				for idx, column := range values.Columns {
					field := stmt.Schema.FieldsByDBName[column.Name]
					if values.Values[i][idx], isZero = field.ValueOf(rv); isZero {
						if field.DefaultValueInterface != nil {
							values.Values[i][idx] = field.DefaultValueInterface
							field.Set(rv, field.DefaultValueInterface)
						} else if field.AutoCreateTime > 0 || field.AutoUpdateTime > 0 {
							field.Set(rv, curTime)
							values.Values[i][idx], _ = field.ValueOf(rv)
						}
					} else if field.AutoUpdateTime > 0 {
						if _, ok := stmt.DB.InstanceGet("gorm:update_track_time"); ok {
							field.Set(rv, curTime)
							values.Values[0][idx], _ = field.ValueOf(rv)
						}
					}
				}

				for _, field := range stmt.Schema.FieldsWithDefaultDBValue {
					if v, ok := selectColumns[field.DBName]; (ok && v) || (!ok && !restricted) {
						if v, isZero := field.ValueOf(rv); !isZero {
							if len(defaultValueFieldsHavingValue[field]) == 0 {
								defaultValueFieldsHavingValue[field] = make([]interface{}, stmt.ReflectValue.Len())
							}
							defaultValueFieldsHavingValue[field][i] = v
						}
					}
				}
			}

			for field, vs := range defaultValueFieldsHavingValue {
				values.Columns = append(values.Columns, clause.Column{Name: field.DBName})
				for idx := range values.Values {
					if vs[idx] == nil {
						values.Values[idx] = append(values.Values[idx], stmt.Dialector.DefaultValueOf(field))
					} else {
						values.Values[idx] = append(values.Values[idx], vs[idx])
					}
				}
			}
		case reflect.Struct:
			values.Values = [][]interface{}{make([]interface{}, len(values.Columns))}
			for idx, column := range values.Columns {
				field := stmt.Schema.FieldsByDBName[column.Name]
				if values.Values[0][idx], isZero = field.ValueOf(stmt.ReflectValue); isZero {
					if field.DefaultValueInterface != nil {
						values.Values[0][idx] = field.DefaultValueInterface
						field.Set(stmt.ReflectValue, field.DefaultValueInterface)
					} else if field.AutoCreateTime > 0 || field.AutoUpdateTime > 0 {
						field.Set(stmt.ReflectValue, curTime)
						values.Values[0][idx], _ = field.ValueOf(stmt.ReflectValue)
					}
				}
			}

			for _, field := range stmt.Schema.FieldsWithDefaultDBValue {
				if v, ok := selectColumns[field.DBName]; (ok && v) || (!ok && !restricted) {
					if v, isZero := field.ValueOf(stmt.ReflectValue); !isZero {
						values.Columns = append(values.Columns, clause.Column{Name: field.DBName})
						values.Values[0] = append(values.Values[0], v)
					}
				}
			}
		default:
			stmt.AddError(gorm.ErrInvalidData)
		}
	}

	if c, ok := stmt.Clauses["ON CONFLICT"]; ok {
		if onConflict, _ := c.Expression.(clause.OnConflict); onConflict.UpdateAll {
			if stmt.Schema != nil && len(values.Columns) > 1 {
				columns := make([]string, 0, len(values.Columns)-1)
				for _, column := range values.Columns {
					if field := stmt.Schema.LookUpField(column.Name); field != nil {
						if !field.PrimaryKey && (!field.HasDefaultValue || field.DefaultValueInterface != nil) && field.AutoCreateTime == 0 {
							columns = append(columns, column.Name)
						}
					}
				}

				onConflict := clause.OnConflict{
					Columns:   make([]clause.Column, len(stmt.Schema.PrimaryFieldDBNames)),
					DoUpdates: clause.AssignmentColumns(columns),
				}

				for idx, field := range stmt.Schema.PrimaryFields {
					onConflict.Columns[idx] = clause.Column{Name: field.DBName}
				}

				stmt.AddClause(onConflict)
			}
		}
	}

	return values
}

ConvertToCreateValues从stmt.DB.NowFunc()获取curTime，然后对于field.AutoCreateTime或者field.AutoUpdateTime大于0的，会设置curTime

setupValuerAndSetter

gorm.io/gorm@v1.20.10/schema/field.go

// create valuer, setter when parse struct
func (field *Field) setupValuerAndSetter() {
	//......

	// Set
	switch field.FieldType.Kind() {
	case reflect.Bool:
		field.Set = func(value reflect.Value, v interface{}) error {
			switch data := v.(type) {
			case bool:
				field.ReflectValueOf(value).SetBool(data)
			case *bool:
				if data != nil {
					field.ReflectValueOf(value).SetBool(*data)
				} else {
					field.ReflectValueOf(value).SetBool(false)
				}
			case int64:
				if data > 0 {
					field.ReflectValueOf(value).SetBool(true)
				} else {
					field.ReflectValueOf(value).SetBool(false)
				}
			case string:
				b, _ := strconv.ParseBool(data)
				field.ReflectValueOf(value).SetBool(b)
			default:
				return fallbackSetter(value, v, field.Set)
			}
			return nil
		}
	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
		field.Set = func(value reflect.Value, v interface{}) (err error) {
			switch data := v.(type) {
			case int64:
				field.ReflectValueOf(value).SetInt(data)
			case int:
				field.ReflectValueOf(value).SetInt(int64(data))
			case int8:
				field.ReflectValueOf(value).SetInt(int64(data))
			case int16:
				field.ReflectValueOf(value).SetInt(int64(data))
			case int32:
				field.ReflectValueOf(value).SetInt(int64(data))
			case uint:
				field.ReflectValueOf(value).SetInt(int64(data))
			case uint8:
				field.ReflectValueOf(value).SetInt(int64(data))
			case uint16:
				field.ReflectValueOf(value).SetInt(int64(data))
			case uint32:
				field.ReflectValueOf(value).SetInt(int64(data))
			case uint64:
				field.ReflectValueOf(value).SetInt(int64(data))
			case float32:
				field.ReflectValueOf(value).SetInt(int64(data))
			case float64:
				field.ReflectValueOf(value).SetInt(int64(data))
			case []byte:
				return field.Set(value, string(data))
			case string:
				if i, err := strconv.ParseInt(data, 0, 64); err == nil {
					field.ReflectValueOf(value).SetInt(i)
				} else {
					return err
				}
			case time.Time:
				if field.AutoCreateTime == UnixNanosecond || field.AutoUpdateTime == UnixNanosecond {
					field.ReflectValueOf(value).SetInt(data.UnixNano())
				} else if field.AutoCreateTime == UnixMillisecond || field.AutoUpdateTime == UnixMillisecond {
					field.ReflectValueOf(value).SetInt(data.UnixNano() / 1e6)
				} else {
					field.ReflectValueOf(value).SetInt(data.Unix())
				}
			case *time.Time:
				if data != nil {
					if field.AutoCreateTime == UnixNanosecond || field.AutoUpdateTime == UnixNanosecond {
						field.ReflectValueOf(value).SetInt(data.UnixNano())
					} else if field.AutoCreateTime == UnixMillisecond || field.AutoUpdateTime == UnixMillisecond {
						field.ReflectValueOf(value).SetInt(data.UnixNano() / 1e6)
					} else {
						field.ReflectValueOf(value).SetInt(data.Unix())
					}
				} else {
					field.ReflectValueOf(value).SetInt(0)
				}
			default:
				return fallbackSetter(value, v, field.Set)
			}
			return err
		}
	case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64:
		field.Set = func(value reflect.Value, v interface{}) (err error) {
			switch data := v.(type) {
			case uint64:
				field.ReflectValueOf(value).SetUint(data)
			case uint:
				field.ReflectValueOf(value).SetUint(uint64(data))
			case uint8:
				field.ReflectValueOf(value).SetUint(uint64(data))
			case uint16:
				field.ReflectValueOf(value).SetUint(uint64(data))
			case uint32:
				field.ReflectValueOf(value).SetUint(uint64(data))
			case int64:
				field.ReflectValueOf(value).SetUint(uint64(data))
			case int:
				field.ReflectValueOf(value).SetUint(uint64(data))
			case int8:
				field.ReflectValueOf(value).SetUint(uint64(data))
			case int16:
				field.ReflectValueOf(value).SetUint(uint64(data))
			case int32:
				field.ReflectValueOf(value).SetUint(uint64(data))
			case float32:
				field.ReflectValueOf(value).SetUint(uint64(data))
			case float64:
				field.ReflectValueOf(value).SetUint(uint64(data))
			case []byte:
				return field.Set(value, string(data))
			case time.Time:
				if field.AutoCreateTime == UnixNanosecond || field.AutoUpdateTime == UnixNanosecond {
					field.ReflectValueOf(value).SetUint(uint64(data.UnixNano()))
				} else if field.AutoCreateTime == UnixMillisecond || field.AutoUpdateTime == UnixMillisecond {
					field.ReflectValueOf(value).SetUint(uint64(data.UnixNano() / 1e6))
				} else {
					field.ReflectValueOf(value).SetUint(uint64(data.Unix()))
				}
			case string:
				if i, err := strconv.ParseUint(data, 0, 64); err == nil {
					field.ReflectValueOf(value).SetUint(i)
				} else {
					return err
				}
			default:
				return fallbackSetter(value, v, field.Set)
			}
			return err
		}
	case reflect.Float32, reflect.Float64:
		field.Set = func(value reflect.Value, v interface{}) (err error) {
			switch data := v.(type) {
			case float64:
				field.ReflectValueOf(value).SetFloat(data)
			case float32:
				field.ReflectValueOf(value).SetFloat(float64(data))
			case int64:
				field.ReflectValueOf(value).SetFloat(float64(data))
			case int:
				field.ReflectValueOf(value).SetFloat(float64(data))
			case int8:
				field.ReflectValueOf(value).SetFloat(float64(data))
			case int16:
				field.ReflectValueOf(value).SetFloat(float64(data))
			case int32:
				field.ReflectValueOf(value).SetFloat(float64(data))
			case uint:
				field.ReflectValueOf(value).SetFloat(float64(data))
			case uint8:
				field.ReflectValueOf(value).SetFloat(float64(data))
			case uint16:
				field.ReflectValueOf(value).SetFloat(float64(data))
			case uint32:
				field.ReflectValueOf(value).SetFloat(float64(data))
			case uint64:
				field.ReflectValueOf(value).SetFloat(float64(data))
			case []byte:
				return field.Set(value, string(data))
			case string:
				if i, err := strconv.ParseFloat(data, 64); err == nil {
					field.ReflectValueOf(value).SetFloat(i)
				} else {
					return err
				}
			default:
				return fallbackSetter(value, v, field.Set)
			}
			return err
		}
	case reflect.String:
		field.Set = func(value reflect.Value, v interface{}) (err error) {
			switch data := v.(type) {
			case string:
				field.ReflectValueOf(value).SetString(data)
			case []byte:
				field.ReflectValueOf(value).SetString(string(data))
			case int, int8, int16, int32, int64, uint, uint8, uint16, uint32, uint64:
				field.ReflectValueOf(value).SetString(utils.ToString(data))
			case float64, float32:
				field.ReflectValueOf(value).SetString(fmt.Sprintf("%."+strconv.Itoa(field.Precision)+"f", data))
			default:
				return fallbackSetter(value, v, field.Set)
			}
			return err
		}
	default:
		fieldValue := reflect.New(field.FieldType)
		switch fieldValue.Elem().Interface().(type) {
		case time.Time:
			field.Set = func(value reflect.Value, v interface{}) error {
				switch data := v.(type) {
				case time.Time:
					field.ReflectValueOf(value).Set(reflect.ValueOf(v))
				case *time.Time:
					if data != nil {
						field.ReflectValueOf(value).Set(reflect.ValueOf(data).Elem())
					} else {
						field.ReflectValueOf(value).Set(reflect.ValueOf(time.Time{}))
					}
				case string:
					if t, err := now.Parse(data); err == nil {
						field.ReflectValueOf(value).Set(reflect.ValueOf(t))
					} else {
						return fmt.Errorf("failed to set string %v to time.Time field %v, failed to parse it as time, got error %v", v, field.Name, err)
					}
				default:
					return fallbackSetter(value, v, field.Set)
				}
				return nil
			}
		case *time.Time:
			field.Set = func(value reflect.Value, v interface{}) error {
				switch data := v.(type) {
				case time.Time:
					fieldValue := field.ReflectValueOf(value)
					if fieldValue.IsNil() {
						fieldValue.Set(reflect.New(field.FieldType.Elem()))
					}
					fieldValue.Elem().Set(reflect.ValueOf(v))
				case *time.Time:
					field.ReflectValueOf(value).Set(reflect.ValueOf(v))
				case string:
					if t, err := now.Parse(data); err == nil {
						fieldValue := field.ReflectValueOf(value)
						if fieldValue.IsNil() {
							if v == "" {
								return nil
							}
							fieldValue.Set(reflect.New(field.FieldType.Elem()))
						}
						fieldValue.Elem().Set(reflect.ValueOf(t))
					} else {
						return fmt.Errorf("failed to set string %v to time.Time field %v, failed to parse it as time, got error %v", v, field.Name, err)
					}
				default:
					return fallbackSetter(value, v, field.Set)
				}
				return nil
			}
		default:
			if _, ok := fieldValue.Elem().Interface().(sql.Scanner); ok {
				// pointer scanner
				field.Set = func(value reflect.Value, v interface{}) (err error) {
					reflectV := reflect.ValueOf(v)
					if !reflectV.IsValid() {
						field.ReflectValueOf(value).Set(reflect.New(field.FieldType).Elem())
					} else if reflectV.Type().AssignableTo(field.FieldType) {
						field.ReflectValueOf(value).Set(reflectV)
					} else if reflectV.Kind() == reflect.Ptr {
						if reflectV.IsNil() || !reflectV.IsValid() {
							field.ReflectValueOf(value).Set(reflect.New(field.FieldType).Elem())
						} else {
							return field.Set(value, reflectV.Elem().Interface())
						}
					} else {
						fieldValue := field.ReflectValueOf(value)
						if fieldValue.IsNil() {
							fieldValue.Set(reflect.New(field.FieldType.Elem()))
						}

						if valuer, ok := v.(driver.Valuer); ok {
							v, _ = valuer.Value()
						}

						err = fieldValue.Interface().(sql.Scanner).Scan(v)
					}
					return
				}
			} else if _, ok := fieldValue.Interface().(sql.Scanner); ok {
				// struct scanner
				field.Set = func(value reflect.Value, v interface{}) (err error) {
					reflectV := reflect.ValueOf(v)
					if !reflectV.IsValid() {
						field.ReflectValueOf(value).Set(reflect.New(field.FieldType).Elem())
					} else if reflectV.Type().AssignableTo(field.FieldType) {
						field.ReflectValueOf(value).Set(reflectV)
					} else if reflectV.Kind() == reflect.Ptr {
						if reflectV.IsNil() || !reflectV.IsValid() {
							field.ReflectValueOf(value).Set(reflect.New(field.FieldType).Elem())
						} else {
							return field.Set(value, reflectV.Elem().Interface())
						}
					} else {
						if valuer, ok := v.(driver.Valuer); ok {
							v, _ = valuer.Value()
						}

						err = field.ReflectValueOf(value).Addr().Interface().(sql.Scanner).Scan(v)
					}
					return
				}
			} else {
				field.Set = func(value reflect.Value, v interface{}) (err error) {
					return fallbackSetter(value, v, field.Set)
				}
			}
		}
	}
}

setupValuerAndSetter方法针对time.Time或*time.Time类型的setter会根据TimeType再做时间精度处理

实例

type Product struct {
	gorm.Model
	Code  string
	Price uint
}

Product内嵌了gorm.Model，内置了ID、CreatedAt、UpdatedAt、DeletedAt属性，同时Create的时候会自动设置CreatedAt、UpdatedAt，Update的时候会自动更新UpdatedAt

小结

gorm定义了ID、CreatedAt、UpdatedAt、DeletedAt属性；其中Create的时候会自动设置CreatedAt、UpdatedAt，Update的时候会自动更新UpdatedAt；CreatedAt、UpdatedAt支持 UnixSecond、UnixMillisecond、UnixNanosecond三种时间精度。

doc

• gorm