序
本文主要研究一下gorm的DeletedAt
DeletedAt
gorm.io/gorm@v1.20.10/soft_delete.go
type DeletedAt sql.NullTime
// Scan implements the Scanner interface.
func (n *DeletedAt) Scan(value interface{}) error {
return (*sql.NullTime)(n).Scan(value)
}
// Value implements the driver Valuer interface.
func (n DeletedAt) Value() (driver.Value, error) {
if !n.Valid {
return nil, nil
}
return n.Time, nil
}
func (n DeletedAt) MarshalJSON() ([]byte, error) {
if n.Valid {
return json.Marshal(n.Time)
}
return json.Marshal(nil)
}
func (n *DeletedAt) UnmarshalJSON(b []byte) error {
if string(b) == "null" {
n.Valid = false
return nil
}
err := json.Unmarshal(b, &n.Time)
if err == nil {
n.Valid = true
}
return err
}
func (DeletedAt) QueryClauses(f *schema.Field) []clause.Interface {
return []clause.Interface{SoftDeleteQueryClause{Field: f}}
}
func (DeletedAt) DeleteClauses(f *schema.Field) []clause.Interface {
return []clause.Interface{SoftDeleteDeleteClause{Field: f}}
}DeletedAt为sql.NullTime类型，它实现了Scanner接口的Scan方法，实现了Valuer接口的Value方法；同时定义了MarshalJSON、UnmarshalJSON方法，还定义了QueryClauses方法，使用的是SoftDeleteQueryClause；DeleteClauses方法使用的是SoftDeleteDeleteClause
SoftDeleteQueryClause
gorm.io/gorm@v1.20.10/soft_delete.go
type SoftDeleteQueryClause struct {
Field *schema.Field
}
func (sd SoftDeleteQueryClause) Name() string {
return ""
}
func (sd SoftDeleteQueryClause) Build(clause.Builder) {
}
func (sd SoftDeleteQueryClause) MergeClause(*clause.Clause) {
}
func (sd SoftDeleteQueryClause) ModifyStatement(stmt *Statement) {
if _, ok := stmt.Clauses["soft_delete_enabled"]; !ok {
if c, ok := stmt.Clauses["WHERE"]; ok {
if where, ok := c.Expression.(clause.Where); ok && len(where.Exprs) > 1 {
for _, expr := range where.Exprs {
if orCond, ok := expr.(clause.OrConditions); ok && len(orCond.Exprs) == 1 {
where.Exprs = []clause.Expression{clause.And(where.Exprs...)}
c.Expression = where
stmt.Clauses["WHERE"] = c
break
}
}
}
}
stmt.AddClause(clause.Where{Exprs: []clause.Expression{
clause.Eq{Column: clause.Column{Table: clause.CurrentTable, Name: sd.Field.DBName}, Value: nil},
}})
stmt.Clauses["soft_delete_enabled"] = clause.Clause{}
}
}SoftDeleteQueryClause的ModifyStatement方法会追加DeletedAt为nil的查询条件
SoftDeleteDeleteClause
gorm.io/gorm@v1.20.10/soft_delete.go
type SoftDeleteDeleteClause struct {
Field *schema.Field
}
func (sd SoftDeleteDeleteClause) Name() string {
return ""
}
func (sd SoftDeleteDeleteClause) Build(clause.Builder) {
}
func (sd SoftDeleteDeleteClause) MergeClause(*clause.Clause) {
}
func (sd SoftDeleteDeleteClause) ModifyStatement(stmt *Statement) {
if stmt.SQL.String() == "" {
curTime := stmt.DB.NowFunc()
stmt.AddClause(clause.Set{{Column: clause.Column{Name: sd.Field.DBName}, Value: curTime}})
stmt.SetColumn(sd.Field.DBName, curTime, true)
if stmt.Schema != nil {
_, queryValues := schema.GetIdentityFieldValuesMap(stmt.ReflectValue, stmt.Schema.PrimaryFields)
column, values := schema.ToQueryValues(stmt.Table, stmt.Schema.PrimaryFieldDBNames, queryValues)
if len(values) > 0 {
stmt.AddClause(clause.Where{Exprs: []clause.Expression{clause.IN{Column: column, Values: values}}})
}
if stmt.ReflectValue.CanAddr() && stmt.Dest != stmt.Model && stmt.Model != nil {
_, queryValues = schema.GetIdentityFieldValuesMap(reflect.ValueOf(stmt.Model), stmt.Schema.PrimaryFields)
column, values = schema.ToQueryValues(stmt.Table, stmt.Schema.PrimaryFieldDBNames, queryValues)
if len(values) > 0 {
stmt.AddClause(clause.Where{Exprs: []clause.Expression{clause.IN{Column: column, Values: values}}})
}
}
}
if _, ok := stmt.Clauses["WHERE"]; !stmt.DB.AllowGlobalUpdate && !ok {
stmt.DB.AddError(ErrMissingWhereClause)
} else {
SoftDeleteQueryClause{Field: sd.Field}.ModifyStatement(stmt)
}
stmt.AddClauseIfNotExists(clause.Update{})
stmt.Build("UPDATE", "SET", "WHERE")
}
}SoftDeleteDeleteClause的ModifyStatement方法会设置DeletedAt为当前时间
interfaces
gorm.io/gorm@v1.20.10/schema/interfaces.go
type GormDataTypeInterface interface {
GormDataType() string
}
type CreateClausesInterface interface {
CreateClauses(*Field) []clause.Interface
}
type QueryClausesInterface interface {
QueryClauses(*Field) []clause.Interface
}
type UpdateClausesInterface interface {
UpdateClauses(*Field) []clause.Interface
}
type DeleteClausesInterface interface {
DeleteClauses(*Field) []clause.Interface
}interfaces包定义了QueryClausesInterface、DeleteClausesInterface接口；schema的Parse方法会回调这些interface的对应方法
小结
gorm的DeletedAt为sql.NullTime类型，它定义了QueryClauses方法，使用的是SoftDeleteQueryClause，它的ModifyStatement方法会追加DeletedAt为nil的查询条件；DeleteClauses方法使用的是SoftDeleteDeleteClause，它的ModifyStatement方法会设置DeletedAt为当前时间。
doc
有疑问加站长微信联系（非本文作者）
