DAO Overview

Gen follows the Configuration As Code practice to generate the DAO interface, here is the introduction to the configuration.

Configuration

You need to write the configuration as a runnable golang program, usually, the program will be organized in a sub-directory of your application.

// 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()
}

Run the above program, it will generate codes into directory ../dal, you can import the dal package in your application and use its interface to query data

gen.Config

type Config struct {
	OutPath      string // query code path
	OutFile      string // query code file name, default: gen.go
	ModelPkgPath string // generated model code's package name
	WithUnitTest bool   // generate unit test for query code

	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
}

Output Options

| Option Name | Description | | FieldNullable | Generate pointer as field's type if column is nullable in database | | FieldCoverable | Generate pointer as field's type if column has default value in database, to avoid zero-value issue, e.g: 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 | Generate with gorm index tag | , for example: gorm:"index:idx_name", default value: false | FieldWithTypeTag | Generate with gorm type tag, for example: gorm:"type:varchar(12)", default value: false |

Refer Database To Structs for more options

Generator Modes

| Tag Name | Description |