ORM Result - Types

1. Data Structures

The data structures of the query results are as follows:

type Value  = *gvar.Var              // Returns table record value
type Record   map[string]Value       // Returns table record key-value pairs
type Result   []Record               // Returns a list of table records

1. Value/Record/Result are result data types for ORM operations.
2. Result represents a list of table records , Record represents a single table record , and Value represents a single key-value pair in a record.
3. Value is an alias type for *gvar.Var, a runtime generic type to support different field types in database tables, facilitating subsequent data type conversion.

For example:

2. Record Data Record

API documentation: https://pkg.go.dev/github.com/gogf/gf/v2/database/gdb

gdb provides a high degree of flexibility and simplicity for table record operations, supporting not only access/manipulation of table records in the form of map but also converting them to struct for processing. Here, we will demonstrate this feature with a simple example.

First, our user table structure is like this (a sample table for simple design):

CREATE TABLE `user` (
  `uid` int(10) unsigned NOT NULL AUTO_INCREMENT,
  `name` varchar(30) NOT NULL DEFAULT '' COMMENT 'Nickname',
  `site` varchar(255) NOT NULL DEFAULT '' COMMENT 'Homepage',
  PRIMARY KEY (`uid`)
) ENGINE=InnoDB AUTO_INCREMENT=1 DEFAULT CHARSET=utf8;

Next, our table data is as follows:

uid  name   site
1    john   https://goframe.org

Finally, our example program is as follows:

package main

import (
    "github.com/gogf/gf/v2/frame/g"
    "github.com/gogf/gf/v2/os/gctx"
)

type User struct {
    Uid  int
    Name string
}

func main() {
    var (
        user *User
        ctx  = gctx.New()
    )
    err := g.DB().Model("user").Where("uid", 1).Scan(&user)
    if err != nil {
        g.Log().Header(false).Fatal(ctx, err)
    }
    if user != nil {
        g.Log().Header(false).Print(ctx, user)
    }
}

After execution, the output is:

{"Uid":1,"Name":"john"}

Here, we define a custom struct containing only Uid and Name properties. As you can see, its properties do not match the fields of the data table, which is one of the flexible features of ORM: supporting specified attribute retrieval.

The gdb.Model.Scan method can convert the queried records into struct objects or arrays of struct objects. Since the parameter passed here is &user i.e., **User type, it will be converted into a struct object. If a []*User type parameter is passed, it will be converted into a struct array. Please see subsequent examples for more. For a detailed introduction to the method, please refer to the chaining operations section.

Attribute Field Mapping Rules:

Note that the key names in map are uid,name,site, while the attributes in struct are Uid,Name. How are they mapped? There are a few simple rules:

1. The matching attribute in struct must be public (starting with a capital letter).
2. Key names in the results will automatically match struct attributes in a case-insensitive , and ignoring-/_/space symbols manner.
3. If the match is successful, the key value is assigned to the attribute. If it cannot be matched, the key value is ignored.

Here are a few matching examples:

Key Name      Struct Attribute     Match
name          Name                 match
Email         Email                match
nickname      NickName             match
NICKNAME      NickName             match
Nick-Name     NickName             match
nick_name     NickName             match
nick_name     Nick_Name            match
NickName      Nick_Name            match
Nick-Name     Nick_Name            match

tip

The conversion from a database result set to struct relies on the gconv.Struct method. Therefore, if you want to achieve custom attribute conversion , and for more detailed mapping rules, please refer to the section on Type Conversion - Struct.

3. Result Data Collection

The Result/Record data types, based on the requirement to manipulate the result set, often need to use specific fields in the records as keys for data retrieval. They include multiple methods for converting to Map/List, as well as common conversions to JSON/XML data structures.

API documentation: https://pkg.go.dev/github.com/gogf/gf/v2/database/gdb

Due to the simplicity of the methods, there are no examples here. However, pay attention to two frequently used methods: Record.Map and Result.List, which are used to convert the ORM query result information into data types suitable for display. Since the field values of the result set are natively of []byte type, although a new Value type has been encapsulated and provides dozens of common type conversion methods (for more, please read the section on Generic), most often we need to directly return the result Result or Record as json or xml data structures, requiring conversion.

Usage example:

package main

import (
    "database/sql"

    "github.com/gogf/gf/v2/frame/g"
    "github.com/gogf/gf/v2/os/gctx"
)

type User struct {
    Uid  int
    Name string
    Site string
}

func main() {
    var (
        user []*User
        ctx  = gctx.New()
    )
    err := g.DB().Model("user").Where("uid", 1).Scan(&user)
    if err != nil && err != sql.ErrNoRows {
        g.Log().Header(false).Fatal(ctx, err)
    }
    if user != nil {
        g.Log().Header(false).Print(ctx, user)
    }
}

After execution, the output is:

[{"Uid":1,"Name":"john","Site":"https://goframe.org"}]