DAO层概览

Gen遵循配置即代码的实践原则来生成DAO层代码，下面是「配置」讲解

配置

你的配置文件需要被撰写成一个可运行的golang程序，通常来说，配置文件应该放在你程序中的一个子目录中。

// configuration.go
package main

import (
  "gorm.io/gen"
  "gorm.io/gorm"
  "gorm.io/driver/sqlite"
)

func main() {
  // Initialize the generator with configuration
  g := gen.NewGenerator(gen.Config{
     OutPath: "../dal", // output directory, default value is ./query
     Mode:    gen.WithDefaultQuery | gen.WithQueryInterface,
     FieldNullable: true,
  })

  // Initialize a *gorm.DB instance
  db, err := gorm.Open(sqlite.Open("test.db"), &gorm.Config{})

  // Use the above `*gorm.DB` instance to initialize the generator,
  // which is required to generate structs from db when using `GenerateModel/GenerateModelAs`
  g.UseDB(db)

  // Generate default DAO interface for those specified structs
  g.ApplyBasic(model.Customer{}, model.CreditCard{}, model.Bank{}, model.Passport{})

  // Generate default DAO interface for those generated structs from database
  companyGenerator := g.GenerateModelAs("company", "MyCompany"),
  g.ApplyBasic(
    g.GenerateModel("users"),
    companyGenerator,
    g.GenerateModelAs("people", "Person",
      gen.FieldIgnore("deleted_at"),
      gen.FieldNewTag("age", `json:"-"`),
    ),
  )

  // Execute the generator
  g.Execute()
}

运行上述代码会在目录../dal中生成相应的DAO层代码，你可以在你的程序中导入dal并使用他们来查询数据

gen.Config

type Config struct {
    OutPath      string // 查询类代码的输出路径
    OutFile      string // 代码输出文件名，默认: gen.go
    ModelPkgPath string // 生成的 model 包名
    WithUnitTest bool   // 是否为生成的查询类代码生成单元测试

    FieldNullable     bool // generate pointer when field is nullable
    FieldCoverable    bool // generate pointer when field has default value, to fix problem zero value cannot be assign: https://gorm.io/docs/create.html#Default-Values
    FieldSignable     bool // detect integer field's unsigned type, adjust generated data type
    FieldWithIndexTag bool // generate with gorm index tag
    FieldWithTypeTag  bool // generate with gorm column type tag

    Mode GenerateMode // generator modes
}

输出配置项

配置	说明
OutPath	生成的查询类代码的输出路径，默认./query
OutFile	生成的文件名，默认gen.go
ModelPkgPath	生成DAO代码的包名，默认是：model
WithUnitTest	是否为DAO包生成单元测试代码，默认：false

生成结构体的配置项

配置	说明
FieldNullable	数据库中的字段可为空，则生成struct字段为指针类型
FieldCoverable	如果数据库中字段有默认值，则生成指针类型的字段，以避免零值（zero-value）问题，见：https://gorm.io/docs/create.html#Default-Values
FieldSignable	Use signable type as field’s type based on column’s data type in database
FieldWithIndexTag	为结构体生成gorm index tag，如gorm:"index:idx_name"，默认：false
FieldWithTypeTag	为结构体生成gorm type tag，如：gorm:"type:varchar(12)"，默认：false

参考 数据库到结构 更多选项

生成器模式

标签名	说明
gen.WithDefaultQuery	是否生成全局变量Q作为DAO接口，如果开启，你可以通过这样的方式查询数据dal.Q.User.First()
gen.WithQueryInterface	生成查询API代码，而不是struct结构体。通常用来MOCK测试
gen.WithoutContext	生成无需传入context参数的代码。如果无需传入context，则代码调用方式如：dal.User.First()，否则，调用方式要像这样：dal.User.WithContext(ctx).First()

DAO Interface

DAO查询样例

type IUserDo interface {
  // Create
  Create(values ...*model.User) error
  CreateInBatches(values []*model.User, batchSize int) error
  Save(values ...*model.User) error

  // Query
  Clauses(conds ...clause.Expression) IUserDo
  As(alias string) gen.Dao
  Columns(cols ...field.Expr) gen.Columns
  Not(conds ...gen.Condition) IUserDo
  Or(conds ...gen.Condition) IUserDo
  Select(conds ...field.Expr) IUserDo
  Where(conds ...gen.Condition) IUserDo
  Order(conds ...field.Expr) IUserDo
  Distinct(cols ...field.Expr) IUserDo
  Omit(cols ...field.Expr) IUserDo
  Join(table schema.Tabler, on ...field.Expr) IUserDo
  LeftJoin(table schema.Tabler, on ...field.Expr) IUserDo
  RightJoin(table schema.Tabler, on ...field.Expr) IUserDo
  Group(cols ...field.Expr) IUserDo
  Having(conds ...gen.Condition) IUserDo
  Limit(limit int) IUserDo
  Offset(offset int) IUserDo
  Scopes(funcs ...func(gen.Dao) gen.Dao) IUserDo
  Unscoped() IUserDo
  Pluck(column field.Expr, dest interface{}) error
  Attrs(attrs ...field.AssignExpr) IUserDo
  Assign(attrs ...field.AssignExpr) IUserDo
  Joins(fields ...field.RelationField) IUserDo
  Preload(fields ...field.RelationField) IUserDo

  Count() (count int64, err error)
  FirstOrInit() (*model.User, error)
  FirstOrCreate() (*model.User, error)
  Returning(value interface{}, columns ...string) IUserDo

  First() (*model.User, error)
  Take() (*model.User, error)
  Last() (*model.User, error)
  Find() ([]*model.User, error)
  FindInBatch(batchSize int, fc func(tx gen.Dao, batch int) error) (results []*model.User, err error)
  FindInBatches(result *[]*model.User, batchSize int, fc func(tx gen.Dao, batch int) error) error
  FindByPage(offset int, limit int) (result []*model.User, count int64, err error)
  ScanByPage(result interface{}, offset int, limit int) (count int64, err error)
  Scan(result interface{}) (err error)

  // Update
  Update(column field.Expr, value interface{}) (info gen.ResultInfo, err error)
  UpdateSimple(columns ...field.AssignExpr) (info gen.ResultInfo, err error)
  Updates(value interface{}) (info gen.ResultInfo, err error)
  UpdateColumn(column field.Expr, value interface{}) (info gen.ResultInfo, err error)
  UpdateColumnSimple(columns ...field.AssignExpr) (info gen.ResultInfo, err error)
  UpdateColumns(value interface{}) (info gen.ResultInfo, err error)
  UpdateFrom(q gen.SubQuery) gen.Dao

  // Delete
  Delete(...*model.User) (info gen.ResultInfo, err error)

  // Common
  Debug() IUserDo
  WithContext(ctx context.Context) IUserDo
  WithResult(fc func(tx gen.Dao)) gen.ResultInfo

  ReadDB() IUserDo
  WriteDB() IUserDo
}

用例

• 如果gen.WithDefaultQuery配置开启，则可使用全局变量Q

import "your_project/dal"

func main() {
  // Initialize a *gorm.DB instance
  db, err := gorm.Open(sqlite.Open("test.db"), &gorm.Config{})

  dal.SetDefault(db)

  // query the first user
  user, err := dal.Q.User.First()
}

• 初始化DAO查询接口

import "your_project/dal"

var Q dal.Query

func main() {
  // Initialize a *gorm.DB instance
  db, err := gorm.Open(sqlite.Open("test.db"), &gorm.Config{})

  Q = dal.Use(db)

  // query the first user
  user, err := Q.User.First()
}

更多使用详情：

• Create
• Update
• Query
• Delete
• Associations
• Transaction