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This article mainly introduces how to use reflection in Go language, which is very detailed and has certain reference value. Friends who are interested must finish reading it!

Overview

Access and modify the program dynamically while the program is running

Reflect godoc: https://golang.org/pkg/reflect/

The reflect package has two data types:

Type: data type [reflect.TypeOf (): is the method to get Type]

Value: type of value [reflect.ValueOf (): is the method to get Value]

Grammar 1. Basic operation

Get variable type

Func TypeOf (I interface {}) Type / / Type is an alias for interface {}

Examples

Reflect.TypeOf (10) / / intreflect.TypeOf (struct {age int} {10}) / / struct {age int}

Get the type of variable

Reflect.TypeOf (struct {age int} {10}). Kind () / / reflect.Structreflect.ValueOf ("hello word"). Kind () / / reflect.String

Get the value of the variable

Func ValueOf (I interface {}) Value / / value is an alias for struct {}

Examples

Reflect.ValueOf ("hello word") / / hello wordreflect.ValueOf (struct {age int} {10}) / / {10} II. Modify the target object

Modify normal type

Str: = "hello word" reflect.ValueOf (& str). Elem (). SetString (Zhang San)

Modify the structure

/ / first step: ValueOf (): pass in the address of a variable Return the address of the variable Elem (): return the original value of the variable elem:=reflect.ValueOf (& variable name). Elem () / second step FieldByName (): pass in the structure field name SetString (): pass in the variable value you want to modify elem.FieldByName ("Name"). SetString ("Li Si") / / define a User structure type User struct {Name string Age int} user: = User {Name: "Zhang San" Age: 10} / / Elem () get the original value of user elem: = reflect.ValueOf (& user). Elem () / / FieldByName () returns the structure field with the given name through Name and modifies the original value elem.FieldByName ("Name") through SetString. SetString ("Li Si") elem.FieldByName ("Age") .SetInt (18) III. Dynamic calling method

No-parameter method

/ / MethodByName (): pass the name of the square Method name must be Call (): method parameter reflect.ValueOf (variable name). MethodByName (method name). Call ([] reflect.Value {}) reflect.ValueOf (variable name). MethodByName (method name) .Call (make ([] reflect.Value) 0) type User struct {Name string `json: "name" name: "Zhang San" `Age int} func (_ User) Say () {fmt.Println ("user talk")} user: = User {Name: "Zhang San", Age: 10} reflect.ValueOf (& user) .MethodByName ("Say"). Call ([] reflect.Value {}) reflect.ValueOf (user) .MethodByName ("Say") .Call make ([] reflect.Value, 0))

Parametric method

Reflect.ValueOf (variable name). MethodByName (method name). Call ([] reflect.Value {reflect.ValueOf ("time to speak"), reflect.ValueOf (1)}) type User struct {Name string `json: "name" name: "Zhang San" `Age int} func (_ User) Say () {fmt.Println ("user talk")} user: = User {Name: "Zhang San" Age: 10} reflect.ValueOf (user) .MethodByName ("SayContent"). Call ([] reflect.Value {reflect.ValueOf ("it's time to talk"), reflect.ValueOf (1)}) Summary

Methods that reflect calls to struct must be public

Nil or [] reflect.Value {} is required when reflection calls a no-parameter method.

Example package mainimport ("fmt"reflect") func main () {/ / 1. Get variable type fmt.Println ("get variable type") fmt.Println (reflect.TypeOf (10)) / / int fmt.Println (reflect.TypeOf (10.0)) / / float64 fmt.Println (reflect.TypeOf (struct {age int} {10})) / / struct {age int} Fmt.Println (reflect.TypeOf (map [string] string {"a": "a"})) / / map [string] string fmt.Println (") / / 2. Get variable value fmt.Println ("get variable value") fmt.Println (reflect.ValueOf ("hello word")) / / hello word fmt.Println (reflect.ValueOf (struct {age int} {10})) / / {10} fmt.Println (reflect.TypeOf (struct {age int} {10}). Kind ()) / / struct / / Type decision Break if t: = reflect.TypeOf (struct {age int} {10}) .Kind () T = = reflect.Struct {fmt.Println ("is a structure")} else {fmt.Println ("not a structure")} / / modify the target object str: = "hello word" / / ordinary variable modification reflect.ValueOf (& str) .Elem () .SetString ("Zhang San") fmt .Println (str) / / structure variable modification user: = User {Name: "Zhang San" Age: 10} / / Elem () gets the original value of user elem: = reflect.ValueOf (& user). Elem () / / FieldByName () returns the structure field with the given name via Name and modifies the original value elem.FieldByName ("Name") by SetString. SetString ("Li Si") elem.FieldByName ("Age"). SetInt (18) fmt.Println ( User) / / gets the value of the tag of the structure fmt.Println (reflect.TypeOf (& user). Elem (). Field (0). Tag.Get ("name")) / / call the no-parameter method reflect.ValueOf (& user) .MethodByName ("Say"). Call ([] reflect.Value {}) reflect.ValueOf (user) .MethodByName ("Say") .Call (make ([] reflect.Value) )) / / call the parametric method reflect.ValueOf (user) .MethodByName ("SayContent"). Call ([] reflect.Value {reflect.ValueOf ("it's time to talk"), reflect.ValueOf (1)}) / / call the local method reflect.ValueOf (Hello). Call ([] reflect.Value {}) reflect.ValueOf (Hello) .call (nil) fmt.Printf ("% # v\ n") Reflect.TypeOf (user) .Field (0)} func Hello () {fmt.Println ("hello")} type Person struct {Name string} type User struct {Person / reflection processes Name string `field as a separate field: "name" name: "Zhang San" `Age int} func (_ User) Say () { Fmt.Println ("user talk")} func (_ User) SayContent (content string An int) {fmt.Println ("user", content, a)} these are all the contents of the article "how to use reflection in Go" Thank you for reading! Hope to share the content to help you, more related knowledge, welcome to follow the industry information channel!

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