1: Introduction
In short: mapstructure is a codec tool for converting between a GO dictionary (map[string]interface{}) and a Go structure.
Core method: (input interface{}, output interface{})
Two: Installation
go get /mitchellh/mapstructure
Source code address:/mitchellh/mapstructure
Official document address://mitchellh/mapstructure
Three: Use
3.1: Simple use cases
Case: parse a JSON string into a dictionary object, and then bind the dictionary to a structure object.
package main
import (
"encoding/json"
"fmt"
"/mitchellh/mapstructure"
"log"
)
type Person struct {
Name string
Age int
Job string
}
func main() {
// Define a JSON string dataJson :=
`{
"name":"renshanwen",
"age":18,
"job": "engineer"
}`
// Parsing JOSN strings into dictionary var m map[string]interface{}
err := ([]byte(dataJson), &m)
if err != nil {
(err)
}
//Bind structure m into structure object p var p Person
(m, &p)
("name is %s, age is %d, job is %s.", , , )
}Output result:
name is renshanwen, age is 18, job is engineer.
3.2: Field tags
Field tag function: defines the field mapping relationship between Go dictionary and GO structure.
Default: mapstruct uses the name of the field in the structure (case insensitive) to make this map.
Case: For example, our structure has a Name field. When mapstructure decodes, it will look for the key name in map[string]interface{}.
Specify the relationship map:
package main
import (
"encoding/json"
"fmt"
"/mitchellh/mapstructure"
"log"
)
type Person struct {
Name string `mapstructure:"user_name"`
Age int `mapstructure:"user_age"`
Job string `mapstructure:"user_job"`
}
func main() {
// Define a JSON string dataJson :=
`{
"user_name":"renshanwen",
"user_age":18,
"user_job": "engineer"
}`
// Parses JSON string into structure var m map[string]interface{}
err := ([]byte(dataJson), &m)
if err != nil {
(err)
}
//Bind structure m into structure object p var p Person
(m, &p)
("name is %s, age is %d, job is %s.", , , )
}3.3: Structural nesting
If the JSON structure in the parameter is relatively complex, multiple structures can be defined, and mapstructure will automatically help us parse.
package main
import (
"encoding/json"
"fmt"
"/mitchellh/mapstructure"
"log"
)
type Person struct {
Name string `mapstructure:"user_name"`
Age int `mapstructure:"user_age"`
Job string `mapstructure:"user_job"`
}
// Worker structure nestingtype Worker struct {
Person Person
Work string `mapstructure:"user_work"`
}
func main() {
// Define a JSON string dataJson := `{
"person":{
"user_name":"renshanwen",
"user_age":18,
"user_job":"engineer"
},
"user_work":"code"
}`
// Parses JSON string into structure var m map[string]interface{}
err := ([]byte(dataJson), &m)
if err != nil {
(err)
}
// Bind structure m to structure object w var w Worker
(m, &w)
("name is %s, age is %d, job is %s ,work is %s.", , , , )
}3.4: Unified storage of unmapped values
You can define a field to receive all unmapdated fields.
Case:
package main
import (
"encoding/json"
"fmt"
"/mitchellh/mapstructure"
"log"
)
type Person struct {
Name string `mapstructure:"user_name"`
Age int `mapstructure:"user_age"`
Job string `mapstructure:"user_job"`
}
// Worker structure nestingtype Worker struct {
Person Person
Work string `mapstructure:"user_work"`
Other map[string]interface{} `mapstructure:",remain"` // Unparsed fields are assigned here by default}
func main() {
// Define a JSON string dataJson := `{
"person":{
"user_name":"renshanwen",
"user_age":18,
"user_job":"engineer"
},
"user_work":"code",
"user_mather": "mather",
"user_baby": "baby"
}`
// Parses JSON string into structure var m map[string]interface{}
err := ([]byte(dataJson), &m)
if err != nil {
(err)
}
// Bind structure m to structure object w var w Worker
(m, &w)
("name is %s, age is %d, job is %s ,work is %s other is %s.", , , , , )
}result:
name is renshanwen, age is 18, job is engineer ,work is code other is map[user_baby:baby user_mather:mather].
3.5: Reverse conversion
Structure—> Dictionary
In reverse decoding, we can set mapstructure: ",omitempty" for certain fields. This way, when these fields are default values, they will not appear in the map[string]interface{} of the structure.
package main
import (
"encoding/json"
"fmt"
"/mitchellh/mapstructure"
)
type Person struct {
Name string `mapstructure:"user_name"`
Age int `mapstructure:"user_age"`
Job string `mapstructure:"user_job,omitempty"` // ,omitempty means that if the structure object does not exist, it will not be parsed into the dictionary.}
// Worker structure nestingtype Worker struct {
Person Person
Work string `mapstructure:"user_work"`
Other map[string]interface{} `mapstructure:",remain"` // Unparsed fields are assigned here by default}
func main() {
// Define a JSON string worker := &Worker{
Work: "code",
}
= "renshanwen"
= 18
var m map[string]interface{}
(worker, &m)
data, _ := (m)
(string(data))
// {"Other":null,"Person":{"user_age":18,"user_name":"renshanwen"},"user_work":"code"}
}3.6: Collect binding information
It can be used to store binding information.
Keys: The binding was successful
Unused: No bound
Unset: Missing
package main
import (
"fmt"
"/mitchellh/mapstructure"
)
type Person struct {
Name string `mapstructure:"user_name"`
Age int `mapstructure:"user_age"`
Job string `mapstructure:"user_job,omitempty"` // ,omitempty means that if the structure object does not exist, it will not be parsed into the dictionary.}
func main() {
m := map[string]interface{}{
"user_name": "renshanwen",
"age": 18,
"job": "engineer",
}
var p Person
var metadata
(m, &p, &metadata)
("keys:%#v unused:%#v Unset:%#v \n", , , )
// keys:[]string{"user_name"} unused:[]string{"age", "job"} Unset:[]string{"user_age", "user_job"}
}The above is a detailed explanation of the detailed content of the Mapstructure library, a structure codec artifact in golang. For more information about go Mapstructure, please follow my other related articles!