让 Go 函数接受不同的结构作为方法的输入

Question

我是 Go 的新手，在尝试为 AWS s3manager 上传器的单元测试创建模拟对象时，我似乎无法理解它的 struct/interface 系统。

在我的包文件中我有：

package uploader

import (
        "fmt"
        "github.com/aws/aws-sdk-go/aws"
        "github.com/aws/aws-sdk-go/aws/session"
        "github.com/aws/aws-sdk-go/service/s3/s3manager"
        "os"
)

func GetS3Uploader() *s3manager.Uploader {
    conf := aws.Config{Region: aws.String("eu-west-1")}
    sess := session.New(&conf)
    uploader := s3manager.NewUploader(sess)
    return uploader
}

func uploadFile(uploader interface{}) {

    uploader.Upload(&s3manager.UploadInput{
       Bucket: aws.String("A"),
       Key:    aws.String("B"),
       Body:   bytes.NewReader([]byte("C")),
    })

}

在匹配的 uploader_test.go 中有以下代码，包含模拟对象：

package uploader_test

import (
    . "github.com/onsi/ginkgo"
    . "github.com/something/reponame/uploader"
    "github.com/aws/aws-sdk-go/service/s3/s3manager"
)

type mockUploadOutput struct {
    Location  string
    VersionID *string
    UploadID  string
}

type mockUploader struct {
}

func (*mockUploader) Upload(input *s3manager.UploadInput) (mockUploadOutput, error) {
    versionID := "TESTVERSION"
    mockUploadResponse := mockUploadOutput{
        Location:  "TESTLOCATION",
        VersionID: &versionID,
        UploadID:  "TESTUPLOADID",
    }
    return mockUploadResponse, nil
}

var _ = Describe("Reportuploader", func() {

    var (
        mockUp mockUploader
    )

    Describe("Upload()", func() {
        Context("With mocked uploader object", func() {
            It("should return the predefined mockUploadResponse", func() {

                uploadFile(mockUp)

            })
        })
    })
})

但是当我尝试运行它时，出现以下错误：

uploader.Upload undefined (type interface {} is interface with no methods)

我的目标是让 uploadFile 函数接受 *s3manager.Uploader 对象和模拟的 mockUploader 作为有效参数，并识别它们的上传方法。我尝试在调用 Upload 方法之前断言类型，但这只给出了不同的错误。谁能帮忙，告诉我我做错了什么？

Answer 1

您将类型签名设置为 func uploadFile(uploader interface{}) {，这意味着它可以接受任何参数，但您不能在 uploader 上调用任何方法，因为您的类型签名 interface{} 没有关于它的任何方法。

看起来你想要做的是：

type Uploader interface {
    Upload(input *s3manager.UploadInput) 
}

func uploadFile(uploader Uploader) {
    uploader.Upload(&s3manager.UploadInput{
        Bucket: aws.String("A"),
        Key:    aws.String("B"),
        Body:   bytes.NewReader([]byte("C")),
    })
}

但是你需要匹配函数签名，看起来其中一个有：

(mockUploadOutput, error)

还有一个

(*s3manager.UploadOutput, error)

所以，我可能会做的只是 return 来自您的模拟的真实 (*s3manager.UploadOutput, error)：

func (*mockUploader) Upload(input *s3manager.UploadInput) (*s3manager.UploadOutput, error) {
  versionID := "TESTVERSION"
  mockUploadResponse := &s3manager.UploadOutput{
      Location:  "TESTLOCATION",
      VersionID: &versionID,
      UploadID:  "TESTUPLOADID",
  }
  return mockUploadResponse, nil
}

Answer 2

您必须为这两种类型提供一个通用的集合 if 方法。 Common 意味着名称、参数类型和 return 类型必须相同。由于您无法更改实际实现，因此您唯一的选择是让模拟模仿 s3 类型。 s3的Upload方法定义如下：

Upload(input *s3manager.UploadInput, options ...func(*s3manager.Uploader)) (*s3manager.UploadOutput, error)

您的模拟必须具有完全相同的方法：

func (*mockUploader) Upload(input *s3manager.UploadInput, options ...func(*s3manager.Uploader)) (*s3manager.UploadOutput, error) {
    // Implementation
}

请注意，您无法更改 return 类型。

现在这两种类型共享一个您可以依赖的接口：

type Uploader interface {
    Upload(input *s3manager.UploadInput, options ...func(*s3manager.Uploader)) (*s3manager.UploadOutput, error)
}

func uploadFile(uploader Uploader) {
}

让 Go 函数接受不同的结构作为方法的输入

Have a Go function accept different structs as input with methods

types

unit-testing

mocking

assertions

go