Go程序中返回的参数太多
我制作了这个简单的软件来连接AWS并生成一个预先签名的put url:Go程序中返回的参数太多,go,Go,我制作了这个简单的软件来连接AWS并生成一个预先签名的put url: package main import ( "fmt" "log" "time" "github.com/minio/minio-go" "github.com/kelseyhightower/envconfig" ) // AWS contains the configuration to connect and create a presigned url on AWS. t
package main
import (
"fmt"
"log"
"time"
"github.com/minio/minio-go"
"github.com/kelseyhightower/envconfig"
)
// AWS contains the configuration to connect and create a presigned url on AWS.
type AWS struct {
Endpoint string
AccessKeyId string
SecretAccessKey string
SSL bool
BucketHost string
BucketKey string
}
func main() {
url, err = generatePresignedPutUrl()
if err != nil {
log.Fatal(err)
}
fmt.Println(url)
}
func generatePresignedPutUrl() {
var aws AWS
if err := envconfig.Process("aws", &aws); err != nil {
return err
}
svc, err := minio.New(aws.Endpoint, aws.AccessKeyId, aws.SecretAccessKey, aws.SSL)
if err != nil {
return err
}
url, err := svc.PresignedPutObject(aws.BucketHost, aws.BucketKey, time.Second * 24 * 60 * 60)
if err != nil {
return url, err
}
}
但是,当我尝试运行go main.go时,我的终端中会显示以下错误:
# command-line-arguments
./main.go:23:5: undefined: url
./main.go:23:10: undefined: err
./main.go:23:39: generatePresignedPutUrl() used as value
./main.go:24:8: undefined: err
./main.go:25:19: undefined: err
./main.go:27:17: undefined: url
./main.go:33:9: too many arguments to return
have (error)
want ()
./main.go:38:9: too many arguments to return
have (error)
want ()
./main.go:43:9: too many arguments to return
have (*url.URL, error)
want ()
我到底做错了什么?几天前我开始学围棋。如果这太明显了,我很抱歉
更新:
我当时能够理解,我应该声明我从GenerateDesignedPutURL返回的内容,但仍然:
package main
import (
"fmt"
"log"
"time"
"github.com/minio/minio-go"
"github.com/kelseyhightower/envconfig"
)
// AWS contains the configuration to connect and create a pre-signed url on AWS.
type AWS struct {
Endpoint string
AccessKeyId string
SecretAccessKey string
SSL bool
BucketHost string
BucketKey string
}
func main() {
url, err := generatePresignedPutUrl()
if err != nil {
log.Fatal(err)
}
fmt.Println(url)
}
// generatePresignedPutUrl connects to S3 and generates a pre-signed put url
// using configurations from environemnt variables.
func generatePresignedPutUrl() (url string, err error) {
var aws AWS
if err := envconfig.Process("aws", &aws); err != nil {
return err
}
svc, err := minio.New(aws.Endpoint, aws.AccessKeyId, aws.SecretAccessKey, aws.SSL)
if err != nil {
return err
}
url, err := svc.PresignedPutObject(aws.BucketHost, aws.BucketKey, time.Second * 24 * 60 * 60)
if err != nil {
return url, err
}
return url
}
错误:
# command-line-arguments
./main.go:36:9: not enough arguments to return
have (error)
want (string, error)
./main.go:41:9: not enough arguments to return
have (error)
want (string, error)
./main.go:44:14: no new variables on left side of :=
./main.go:44:14: cannot assign *url.URL to url (type string) in multiple assignment
./main.go:49:5: not enough arguments to return
have (string)
want (string, error)
从…的godoc。返回一个值和一个错误
i、 e.url,err:=svc.PresignedPutObjectaws.BucketHost,aws.BucketKey,time.Second*24*60*60
从代码中,您可能想要url字符串,对吗
如果这是您想要的,您可以参考以下godoc中的示例:
此外,您不能只从函数返回一个错误,您必须返回一个字符串和一个错误
修改代码以返回url字符串,您可能可以执行以下操作:
func generatePresignedPutUrl() (url string, err error) {
var aws AWS
if err := envconfig.Process("aws", &aws); err != nil {
return "", err
}
svc, err := minio.New(aws.Endpoint, aws.AccessKeyId, aws.SecretAccessKey, aws.SSL)
if err != nil {
return "", err
}
u, err := svc.PresignedPutObject(aws.BucketHost, aws.BucketKey, time.Second * 24 * 60 * 60)
if err != nil {
return "", err
}
url = u.String()
return url, err
}
首先,你应该按照JimB说的去做。不到一个小时,你就会知道这个问题的答案 请注意,您正在GeneratePressignedPutURL的返回声明中声明url和err,看起来这不是您想要做的。您应将函数声明更改为:
func generatePresignedPutUrl() (url string, err error) {
致:
现在,让我们按顺序解决您的错误:
错误1:参数不足,无法返回
错误是,Go并不是很神秘。没有足够的参数来返回它所说的内容。您试图返回的参数比您应该返回的参数少
在Go中,可以从函数返回多个值,但无论返回多少值,始终需要返回所有值。函数func generatePressignedPutUrl url string,err error需要一个字符串和一个错误,但在return err中,您只是返回err,它属于error类型,因此您缺少一个字符串,在这种情况下,因为函数返回空字符串时出错。要修复它,只需执行以下操作:返回,改为err
错误2:在以下对象的左侧没有新变量:=
这也不是很神秘。这意味着:=左侧的变量都不是新的。:=声明一个新变量,然后将值赋给该变量,因此如果该变量不是新的,则在尝试声明时会出现错误。在本例中,您在函数声明中声明了url,在函数的第二行声明了err。要修复它,请替换:
url, err := svc.PresignedPutObject(aws.BucketHost, aws.BucketKey, time.Second * 24 * 60 * 60)
用于:
错误3:无法将*url.url分配给多重分配中的url类型字符串
您正在尝试将type*url.url分配给变量url,该变量是字符串。在Go中,如果变量来自同一类型,则只能为变量赋值。是url.url类型的文档。要解决此问题,请执行以下操作:
rawUrl, err := svc.PresignedPutObject(aws.BucketHost, aws.BucketKey, time.Second * 24 * 60 * 60)
if err != nil {
return "", err
}
return rawUrl.String() // rawUrl is of type *url.URL, so get it's string representation
如果函数未声明任何返回值,则不能返回值。试着从开始。是的,在你发表评论之前我已经弄清楚了,但是仍然不清楚应该把什么作为generateDesignedPutURL的第一个值。您可以检查我的更新吗?错误消息中说:无法将*url.url分配给url类型字符串-您有一个*url.url
url, err = svc.PresignedPutObject(aws.BucketHost, aws.BucketKey, time.Second * 24 * 60 * 60)
rawUrl, err := svc.PresignedPutObject(aws.BucketHost, aws.BucketKey, time.Second * 24 * 60 * 60)
if err != nil {
return "", err
}
return rawUrl.String() // rawUrl is of type *url.URL, so get it's string representation