func (c *Callback) Update() *CallbackProcessor {
	return &CallbackProcessor{kind: "update", parent: c}
}
Update could be used to register callbacks for updating object, refer `Create` for usage
package gorm
import "log"
var DefaultCallback = &Callback{}
type Callback struct {
	creates    []*func(scope *Scope)
	updates    []*func(scope *Scope)
	deletes    []*func(scope *Scope)
	queries    []*func(scope *Scope)
	rowQueries []*func(scope *Scope)
	processors []*CallbackProcessor
}
type CallbackProcessor struct {
	name      string               
	before    string               
	after     string               
	replace   bool                 
	remove    bool                 
	kind      string               
	processor *func(scope *Scope)  
	parent    *Callback
}
func (c *Callback) clone() *Callback {
	return &Callback{
		creates:    c.creates,
		updates:    c.updates,
		deletes:    c.deletes,
		queries:    c.queries,
		rowQueries: c.rowQueries,
		processors: c.processors,
	}
}
func (c *Callback) Create() *CallbackProcessor {
	return &CallbackProcessor{kind: "create", parent: c}
}