Database To Structs

Quick Start

Gen supports generate structs from databases following GORM conventions, it can be used like:

package main

import "gorm.io/gen"

func main() {
  g := gen.NewGenerator(gen.Config{
    OutPath: "../query",
    Mode: gen.WithoutContext|gen.WithDefaultQuery|gen.WithQueryInterface, // generate mode
  })

  // gormdb, _ := gorm.Open(mysql.Open("root:@(127.0.0.1:3306)/demo?charset=utf8mb4&parseTime=True&loc=Local"))
  g.UseDB(gormdb) // reuse your gorm db

  // Generate basic type-safe DAO API for struct `model.User` following conventions

  g.ApplyBasic(
  // Generate struct `User` based on table `users`
  g.GenerateModel("users"),

  // Generate struct `Employee` based on table `users`
 g.GenerateModelAs("users", "Employee"),


// Generate struct `User` based on table `users` and generating options
g.GenerateModel("users", gen.FieldIgnore("address"), gen.FieldType("id", "int64")),

// Generate struct `Customer` based on table `customer` and generating options
// customer table may have a tags column, it can be JSON type, gorm/gen tool can generate for your JSON data type
g.GenerateModel("customer", gen.FieldType("tags", "datatypes.JSON")),

  )
g.ApplyBasic(
// Generate structs from all tables of current database
g.GenerateAllTable()...,
)
  // Generate the code
  g.Execute()
}

Methods Template

When generating structs from database, you can also generate methods with a template for them by the way, for example:

type CommonMethod struct {
    ID   int32
    Name *string
}

func (m *CommonMethod) IsEmpty() bool {
    if m == nil {
        return true
    }
    return m.ID == 0
}

func (m *CommonMethod) GetName() string {
    if m == nil || m.Name == nil {
        return ""
    }
    return *m.Name
}

// Add IsEmpty method to the generated `People` struct
g.GenerateModel("people", gen.WithMethod(CommonMethod{}.IsEmpty))

// Add all methods defined on `CommonMethod` to the generated `User` struct
g.GenerateModel("user", gen.WithMethod(CommonMethod{}))

The generated code would look like this:

// Generated Person struct
type Person struct {
  // ...
}

func (m *Person) IsEmpty() bool {
  if m == nil {
    return true
  }
  return m.ID == 0
}


// Generated User struct
type User struct {
  // ...
}

func (m *User) IsEmpty() bool {
  if m == nil {
    return true
  }
  return m.ID == 0
}

func (m *User) GetName() string {
  if m == nil || m.Name == nil {
    return ""
  }
  return *m.Name
}

DIY TableName

When generating structs from database, you can also diy table name for them by the way, for example:

type CommonMethod struct {
    ID   int32
    Name *string
}

// TableName 
func (m CommonMethod) TableName() string {
    return "@@table"
}

// TableName table name with gorm NamingStrategy
func (m CommonMethod) TableName(namer schema.Namer) string {
    if namer == nil {
        return "@@table"
    }
    return namer.TableName("@@table")
}

// DIY TableName method for the generated `User` struct
g.GenerateModel("user", gen.WithMethod(CommonMethod{}.TableName))

// DIY TableName method for the generated all struct
g.WithOpts(gen.WithMethod(CommonMethod{}.TableName))

// Set Default DIY TableName method for the generated all struct
g.WithOpts(gen.WithMethod(gen.DefaultMethodTableWithNamer))

Field Options

Following are options that can be used during GenerateModel/GenerateModelAs

FieldNew           // create new a field
FieldIgnore        // ignore field
FieldIgnoreReg     // ignore field (match with regexp)
FieldRename        // rename field in the struct
FieldComment       // specify field comment in generated struct
FieldType          // specify the field type
FieldTypeReg       // specify field type (match with regexp)
FieldGenType       // specify field gen type
FieldGenTypeReg    // specify field gen type (match with regexp)
FieldTag           // specify gorm and json tag
FieldJSONTag       // specify json tag
FieldJSONTagWithNS // specify json tag with name strategy
FieldGORMTag       // specify gorm tag
FieldNewTag        // append new tag
FieldNewTagWithNS  // specify the new tag with name strategy
FieldTrimPrefix    // trim column prefix
FieldTrimSuffix    // trim column suffix
FieldAddPrefix     // add the prefix to struct field's name
FieldAddSuffix     // add the suffix to struct field's name
FieldRelate        // specify relationship with other tables
FieldRelateModel   // specify the relationship with existing models

Global Generating Options

Gen has some global options that could be setup in the gen.Config, here is the list:

g := gen.NewGenerator(gen.Config{
  // if you want the nullable field generation property to be pointer type, set FieldNullable true
  FieldNullable: true,
  // if you want to assign field which has a default value in the `Create` API, set FieldCoverable true, reference: https://gorm.io/docs/create.html#Default-Values
  FieldCoverable: true,
  // if you want to generate field with unsigned integer type, set FieldSignable true
  FieldSignable: true,
  // if you want to generate index tags from database, set FieldWithIndexTag true
  FieldWithIndexTag: true,
  // if you want to generate type tags from database, set FieldWithTypeTag true
  FieldWithTypeTag: true,
  // if you need unit tests for query code, set WithUnitTest true
  WithUnitTest: true,
})

// WithDbNameOpts set get database name function
WithDbNameOpts(opts ...model.SchemaNameOpt)

// WithTableNameStrategy specify table name naming strategy, only work when syncing table from db
WithTableNameStrategy(ns func(tableName string) (targetTableName string))

// WithModelNameStrategy specify model struct name naming strategy, only work when syncing table from db
// If an empty string is returned, the table will be ignored
WithModelNameStrategy(ns func(tableName string) (modelName string))

// WithFileNameStrategy specify file name naming strategy, only work when syncing table from db
WithFileNameStrategy(ns func(tableName string) (fileName string))

// WithJSONTagNameStrategy specify json tag naming strategy
WithJSONTagNameStrategy(ns func(columnName string) (tagContent string))

// WithDataTypeMap specify data type mapping relationship, only work when syncing table from db
WithDataTypeMap(newMap map[string]func(gorm.ColumnType) (dataType string))

// WithImportPkgPath specify import package path
WithImportPkgPath(paths ...string)

// WithOpts specify global model options
WithOpts(opts ...ModelOpt)

Data Mapping

Specify datatype mapping between field type and db column type.

var dataMap = map[string]func(gorm.ColumnType) (dataType string){
    // int mapping
    "int": func(columnType gorm.ColumnType) (dataType string) {
        if n, ok := columnType.Nullable(); ok && n {
            return "*int32"
        }
        return "int32"
    },

    // bool mapping
    "tinyint": func(columnType gorm.ColumnType) (dataType string) {
        ct, _ := columnType.ColumnType()
        if strings.HasPrefix(ct, "tinyint(1)") {
            return "bool"
        }
        return "byte"
    },
}

g.WithDataTypeMap(dataMap)

Generate From Sql

Gen supports generate structs from sql following GORM conventions, it can be used like:

package main

import (
    "gorm.io/gorm"
    "gorm.io/rawsql"
)

func main() {
  g := gen.NewGenerator(gen.Config{
    OutPath: "../query",
    Mode: gen.WithoutContext|gen.WithDefaultQuery|gen.WithQueryInterface, // generate mode
  })
  // https://github.com/go-gorm/rawsql/blob/master/tests/gen_test.go
  gormdb, _ := gorm.Open(rawsql.New(rawsql.Config{
        //SQL:      rawsql,                      //create table sql
        FilePath: []string{
            //"./sql/user.sql", // create table sql file
            "./test_sql", // create table sql file directory
        },
    }))
  g.UseDB(gormdb) // reuse your gorm db

  // Generate basic type-safe DAO API for struct `model.User` following conventions

  g.ApplyBasic(
  // Generate struct `User` based on table `users`
  g.GenerateModel("users"),

  // Generate struct `Employee` based on table `users`
 g.GenerateModelAs("users", "Employee"),

  )
g.ApplyBasic(
// Generate structs from all tables of current database
g.GenerateAllTable()...,
)
  // Generate the code
  g.Execute()
}