Ent
是一个简单且功能强大的Go
语言ORM
框架,易于构建和维护应用程序与大数据模型。本文主要介绍在Ent
中如何实现软删除。
拦截器Interceptors
是各种类型的Ent
查询的执行中间件,应用于读取路径并作为接口实现,允许它们在不同阶段拦截和修改查询,从而提供对查询行为的更细粒度的控制。
要定义一个Interceptor
,用户可以声明一个实现该Intercept
方法的结构或使用预定义的 ent.InterceptFunc
适配器。
ent.InterceptFunc(func(next ent.Querier) ent.Querier {
return ent.QuerierFunc(func(ctx context.Context, query ent.Query) (ent.Value, error) {
// Do something before the query execution.
value, err := next.Query(ctx, query)
// Do something after the query execution.
return value, err
})
})
在上面的示例中,ent.Query
代表生成的查询生成器(例如,ent.<T>Query
)并且访问其方法需要类型断言。例如:
ent.InterceptFunc(func(next ent.Querier) ent.Querier {
return ent.QuerierFunc(func(ctx context.Context, query ent.Query) (ent.Value, error) {
if q, ok := query.(*ent.UserQuery); ok {
q.Where(user.Name("a8m"))
}
return next.Query(ctx, query)
})
})
在命令行界面执行如下代码:
$ go run -mod=mod entgo.io/ent/cmd/ent generate --feature intercept,schema/snapshot ./schema
schema
中使用了interceptors
,有可能在schema
包和生成的ent
包之间循环导入。为了避免这种情况,ent
生成一个ent/runtime
包,负责在运行时注册模式挂钩。如下所示:import _ "<project>/ent/runtime"
package schema
import (
"context"
"entgo.io/ent"
"entgo.io/ent/dialect/sql"
"entgo.io/ent/schema/field"
"entgo.io/ent/schema/mixin"
"fmt"
gen "<project>/ent"
"<project>/ent/hook"
"<project>/ent/intercept"
"time"
)
// SoftDeleteMixin implements the soft delete pattern for schemas.
type SoftDeleteMixin struct {
mixin.Schema
}
// Fields of the SoftDeleteMixin.
func (SoftDeleteMixin) Fields() []ent.Field {
return []ent.Field{
field.Time("delete_time").
Optional(),
}
}
type softDeleteKey struct{}
// SkipSoftDelete returns a new context that skips the soft-delete interceptor/mutators.
func SkipSoftDelete(parent context.Context) context.Context {
return context.WithValue(parent, softDeleteKey{}, true)
}
// Interceptors of the SoftDeleteMixin.
func (d SoftDeleteMixin) Interceptors() []ent.Interceptor {
return []ent.Interceptor{
intercept.TraverseFunc(func(ctx context.Context, q intercept.Query) error {
// Skip soft-delete, means include soft-deleted entities.
if skip, _ := ctx.Value(softDeleteKey{}).(bool); skip {
return nil
}
d.P(q)
return nil
}),
}
}
// Hooks of the SoftDeleteMixin.
func (d SoftDeleteMixin) Hooks() []ent.Hook {
return []ent.Hook{
hook.On(
func(next ent.Mutator) ent.Mutator {
return ent.MutateFunc(func(ctx context.Context, m ent.Mutation) (ent.Value, error) {
// Skip soft-delete, means delete the entity permanently.
if skip, _ := ctx.Value(softDeleteKey{}).(bool); skip {
return next.Mutate(ctx, m)
}
mx, ok := m.(interface {
SetOp(ent.Op)
Client() *gen.Client
SetDeleteTime(time.Time)
WhereP(...func(*sql.Selector))
})
if !ok {
return nil, fmt.Errorf("unexpected mutation type %T", m)
}
d.P(mx)
mx.SetOp(ent.OpUpdate)
mx.SetDeleteTime(time.Now())
return mx.Client().Mutate(ctx, m)
})
},
ent.OpDeleteOne|ent.OpDelete,
),
}
}
// P adds a storage-level predicate to the queries and mutations.
func (d SoftDeleteMixin) P(w interface{ WhereP(...func(*sql.Selector)) }) {
w.WhereP(
sql.FieldIsNull(d.Fields()[0].Descriptor().Name),
)
}
// Pet holds the schema definition for the Pet entity.
type Pet struct {
ent.Schema
}
// Mixin of the Pet.
func (Pet) Mixin() []ent.Mixin {
return []ent.Mixin{
SoftDeleteMixin{},
}
}
// Filter out soft-deleted entities.
pets, err := client.Pet.Query().All(ctx)
if err != nil {
return err
}
// Include soft-deleted entities.
pets, err := client.Pet.Query().All(schema.SkipSoftDelete(ctx))
if err != nil {
return err
}
更多关于interceptors
的介绍请看官方文档。