小编典典

不能使用函数(func()类型)作为参数中的类型

go

package main

import (
    "log"
    "strings"

    "asl.com/asl"
)

/*
Trivial service to demonstrate chaining service together
Message starts in originator, travels through a couple formatters, and then gets back to originator
*/

type MessageTest struct {
    Body string `json:"body"`
}
var s *asl.Service
func main() {
    var (
        err error
        cid string
    )
    //var m MessageDelivery
       var g asl.MessageHandler
       g = UpperCaseHandler

    //  UpperCaser := asl.NewService("UpperCaser", "", false)
    UpperCaser := asl.NewService("UpperCaser")
    if err = UpperCaser.ConsumeFunc("asl-service-uc", []string{"asl-service-uc"},func() interface{} {
        return ""
    },g); err != nil {
        log.Fatalf("Error starting consumer: %v", err)
    }
    //  Repeater := asl.NewService("Repeater", "", false)
    Repeater := asl.NewService("Repeater")
    if err = Repeater.ConsumeFunc("asl-service-repeat", []string{"asl-service-repeat"}, func() interface{} {
        return ""
    }, RepeatHandler); err != nil {
        //if err = Repeater.ConsumeFunc("asl-service-repeat", []string{"asl-service-repeat"}, mg asl.MessageGenerator, mh asl.MessageHandler); err != nil {
        log.Fatalf("Error starting consumer: %v", err)
    }

    //  originator := asl.NewService("Originator", "", false)
    originator := asl.NewService("Originator")

    deliveryChan := make(chan asl.MessageDelivery)
    m := asl.MessagePublishing{
        Message:     MessageTest{"this is a test"},
        RoutingKeys: []string{"asl-service-uc", "asl-service-repeat"},
    }
    if cid, err = originator.RPCPublish(m, deliveryChan); err != nil {
        log.Fatalf("Failed to publish: %v", err)
    }

    message := <-deliveryChan
    log.Printf("Originator Got: %+v", message.Message)
    originator.RemoveQueue(cid)
    UpperCaser.Wait()
}

func UpperCaseHandler(md asl.MessageDelivery) {
     s.Reply(MessageTest{strings.ToUpper(md.Message.(string))}, md.Delivery)
}

func RepeatHandler(md asl.MessageDelivery) {
     s.Reply(MessageTest{strings.Repeat(md.Message.(string), 5)}, md.Delivery)
}


package asl
Error

./chains.go:26:10:不能在作业中使用UpperCaseHandler(typefunc(asl.MessageDelivery))作为asl.MessageHandler类型./chains.go:37:86:无法使用RepeatHandler(类型func(asl.MessageDelivery))与Repeater.ConsumeFunc的参数中的asl.MessageHandler类型相同

type MessageDelivery struct {
    Delivery amqp.Delivery
    Message  interface{}
    Error    error
    Context  *Context
}    
type MessageGenerator func() interface{}

type MessageHandler func(MessageDelivery) (interface{}, error)

我试图运行代码,哪里出了问题,我该如何正确地将函数作为参数传递给另一个函数。该函数返回接口和错误。虽然函数以MessageDelivery
Struct作为参数,但是函数签名是相同的。


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2020-07-02

共1个答案

小编典典

您正确地将该函数作为参数传递,但是它们与预期的签名不匹配。将功能更改为:

func UpperCaseHandler(md busboy.MessageDelivery) (interface{}, error} {
     s.Reply(MessageTest{strings.ToUpper(md.Message.(string))}, md.Delivery)
     return nil, nil
}

func RepeatHandler(md busboy.MessageDelivery) (interface{}, error} {
     s.Reply(MessageTest{strings.Repeat(md.Message.(string), 5)}, md.Delivery)
     return nil, nil
}
2020-07-02