检查方法类型是否与函数类型匹配

Question

给定以下示例，如何检查方法是否与函数签名匹配？package mainimport (    "fmt"    "context"    "reflect")// signature to checktype Fn func(context.Context)type testStruct struct {}func (*testStruct) DoSomething(context.Context){}func (*testStruct) DoSomethingElse([]byte){}func main() {    structType := reflect.TypeOf(&testStruct{})    for i := 0; i < structType.NumMethod(); i++ {        fmt.Println("======================")        method := structType.Method(i)        fmt.Println(method.Name)        fmt.Println(method.Type.String())        // compare method and Fn signature    }}https://play.golang.org/p/rIDfp0E14ge

Answer 1

1.使用reflect.Value.Type().ConvertibleTo

注意reflect.ValueOfinstedreflect.TypeOf

package main

import (

    "context"

    "fmt"

    "reflect"

)

type Fn func(context.Context)

type testStruct struct{}

func (*testStruct) DoSomething(context.Context)           {}

func (*testStruct) DoSomethingElse([]byte)                {}

func (*testStruct) DoSomethingElse2(context.Context) error { return nil }

func main() {

    structType := reflect.ValueOf(&testStruct{})

    for i := 0; i < structType.NumMethod(); i++ {

        fmt.Println("======================")

        method := structType.Method(i)

        // compare method and Fn

        if method.Type().ConvertibleTo(reflect.TypeOf((Fn)(nil))) {

            fmt.Println("function of correct type")

        }

    }

}

https://play.golang.org/p/A9_bpURinad

2. 分别检查输入和输出

package main

import (

    "context"

    "fmt"

    "reflect"

)

type Fn func(context.Context)

type testStruct struct{}

func (*testStruct) DoSomething(context.Context) {}

func (*testStruct) DoSomethingElse([]byte)      {}

func main() {

    structType := reflect.TypeOf(&testStruct{})

    rctx := reflect.TypeOf(new(context.Context)).Elem()

    for i := 0; i < structType.NumMethod(); i++ {

        fmt.Println("======================")

        method := structType.Method(i)

        fmt.Println(method.Name)

        fmt.Println(method.Type.String())

        if method.Type.NumIn() != 2 {

            fmt.Println("wrong number of inputs, expected 1")

            continue

        }

        if method.Type.In(1) != rctx {

            fmt.Println("input of wrong type, expected context.Context")

            continue

        }

        if method.Type.NumOut() != 0 {

            fmt.Println("wrong number of outputs, expected 0")

            continue

        }

        fmt.Printf("%v is a function of correct type\n", method.Name)

    }

}

https://play.golang.org/p/YDsJ9MSiumF