意外的多次返回

Question

我正在构建一个应用程序，我从多个来源获得穆斯林祈祷数据。第一个是S3，第二个是aladhan(一个公共api)。我只想从S3中不可用的aladhan中获取数据。如果我必须从公共来源获取数据，那么我就把它上传到我的s3。

代码如下:

这是我的接口循环代码。我输入了print语句，以显示我两次运行返回语句，一次返回结构体中有数据，第二次结构体为nil。

// prayeriface.go
package prayer
import (
"fmt"
)
type MonthPrayerIface interface {
GetMonthPrayer(input *LookupInput) (*PreCurrNextMonthPrayer, error)
}
type PreCurrNextMonthPrayer struct {
custData          *LookupInput
CurrentMonthData  *PCal
PreviousMonthData *PCal
NextMonthData     *PCal
prayers []MonthPrayerIface
}
func (p *PreCurrNextMonthPrayer) GetMonthPrayers() (*PreCurrNextMonthPrayer, error) {
var err error
var monthlyData *PreCurrNextMonthPrayer
defer func() {
fmt.Printf("return monthlyData address & value = %p %vn", monthlyData, monthlyData)
}()
for k, data := range p.prayers {
fmt.Printf("loop = %v, data= %T %vn", k, monthlyData, monthlyData)
monthlyData, err = data.GetMonthPrayer(p.custData)
fmt.Printf("terr= %vn", err)
fmt.Printf("tmonthlyData= %p %vn", monthlyData, monthlyData)
if err == nil {
fmt.Printf("loop-return: err == nil n")
return monthlyData, nil
}
}
if err == nil {
fmt.Printf("post-loop:n")
fmt.Printf("tmonthlyData= %p %vn", monthlyData, monthlyData)
return monthlyData, nil
}
return nil, fmt.Errorf("unable to get prayer data from all sources %s", err)
}
func NewMonthPrayer(input *LookupInput, prayers ...MonthPrayerIface) (*PreCurrNextMonthPrayer, error) {
var err error
t := &PreCurrNextMonthPrayer{
custData: input,
prayers:  prayers,
}
t, err = t.GetMonthPrayers()
if err != nil {
return nil, err
}
return t, nil
}

如你所见，我正在循环一个名为GetMonthPrayer

的接口结构方法这是我的s3源

// s3.go
package prayer
import (
"bytes"
"encoding/json"
"errors"
"fmt"
"github.com/aws/aws-sdk-go/aws"
"github.com/aws/aws-sdk-go/service/s3"
"io"
awsservices "prayer-times/src/aws"
)
// S3Store s3 storage object for prayer calendars
type S3Store struct {
data *PCal
}
// GetMonthPrayer retrieves prayer data from s3, otherwise from aladhan
func (s *S3Store) GetMonthPrayer(input *LookupInput) (*PreCurrNextMonthPrayer, error) {
mPrayer := new(PreCurrNextMonthPrayer)
fmt.Println("attempting to retrieve prayer data from s3")
s3Client := awsservices.NewS3Service()
pMonthInput := &LookupInput{
Country:  input.Country,
ZipCode:  input.ZipCode,
custTime: input.custTime.AddDate(0, -1, 0),
}
nMonthInput := &LookupInput{
Country:  input.Country,
ZipCode:  input.ZipCode,
custTime: input.custTime.AddDate(0, 1, 0),
}
// s3Pdata retrieves data from S3 and
s3pData := func(input *LookupInput) (*PCal, error) {
pCalendar := new(PCal)
data, err := s3Client.GetObject(&s3.GetObjectInput{
Bucket: aws.String(bucket),
Key: aws.String(
fmt.Sprintf(
"%s/%d/%d/%d",
input.Country,
input.ZipCode,
input.custTime.Year(),
input.custTime.Month())),
})
if err != nil {
return nil, err
}
if data == nil {
return nil, errors.New("error data from s3 is nil")
}
defer func() {
err := data.Body.Close()
if err != nil {
fmt.Printf("unable to close s3 body: %s", err)
}
}()
s3buf := bytes.NewBuffer(nil)
if _, err := io.Copy(s3buf, data.Body); err != nil {
return nil, err
}
dataBytes := s3buf.Bytes()
decoder := json.NewDecoder(bytes.NewReader(dataBytes))
err = decoder.Decode(&pCalendar)
if err != nil {
fmt.Printf("unable to decode json: %s", err)
}
return pCalendar, nil
}
aladhanData := new(AladhanStore)
getAladhanData := func(input *LookupInput) (*PreCurrNextMonthPrayer, error) {
data, err := aladhanData.GetMonthPrayer(input)
if err != nil {
return nil, err
}
return data, nil
}
// Get current data from s3, if not s3, then get all three from aladhan
cMonthS3Data, err := s3pData(input)
pMonthS3Data, err := s3pData(pMonthInput)
nMonthS3Data, err := s3pData(nMonthInput)
if err != nil {
adata, err := getAladhanData(input)
if err != nil {
fmt.Printf("err: %s", err)
return nil, err
}
return adata, nil
}
mPrayer.CurrentMonthData = cMonthS3Data
// Get previous month data from s3, if not s3, then get all three from aladhan
mPrayer.PreviousMonthData = pMonthS3Data
// Get next month data from s3, if not s3, then get all three from aladhan
mPrayer.NextMonthData = nMonthS3Data
return mPrayer, nil
}

这是我的aladhan来源

// aladhan.go
package prayer
import (
"bytes"
"encoding/json"
"fmt"
"github.com/aws/aws-sdk-go/aws"
"github.com/aws/aws-sdk-go/service/s3/s3manager"
"golang.org/x/sync/errgroup"
"io"
"log"
awsservices "prayer-times/src/aws"
"prayer-times/src/urljsonoutput"
"prayer-times/src/zipcoordinates"
)
var (
aladhanURL string = "https://api.aladhan.com/v1/calendar?"
)
// PCal contains the prayer times of the month as well as the return code
type PCal struct {
Code   int    `json:"code"`
Status string `json:"status"`
Data   []struct {
Timings DailyPrayers
}
}
/*
AladhanData returns the total monthly prayers of given month, coordinates, and zip from aladhan.
https://api.aladhan.com/v1/calendar?latitude=51.508515&longitude=-0.1254872&method=1&month=4&year=2017
*/
func AladhanData(input *LookupInput) *PCal {
coordinates := zipcoordinates.HereCoordinates(&zipcoordinates.GeoLocationInput{
PostalCode:  input.ZipCode,
CountryCode: input.Country,
})
respStruct := new(PCal)
_, err := urljsonoutput.GetURLJSON(fmt.Sprintf(
"%slatitude=%v&longitude=%v&method=%v&month=%v&year=%v",
aladhanURL,
coordinates.Items[0].Position.Latitude,
coordinates.Items[0].Position.Longitude,
input.Method,
int(input.custTime.Month()),
input.custTime.Year()), respStruct)
if err != nil {
log.Fatalf("unable to pull monthly prayer data %v", err)
}
return respStruct
}
// AladhanStore struct to interact with interface for GetMonthPrayer
type AladhanStore struct {
data *PCal
}
// GetMonthPrayer Pulls prayer data from aladhan
func (a *AladhanStore) GetMonthPrayer(input *LookupInput) (*PreCurrNextMonthPrayer, error) {
mPrayer := new(PreCurrNextMonthPrayer)
// Return prayer data from aladhan
custPMonthTime := input.custTime.AddDate(0, -1, 0)
pMonthLookupInput := new(LookupInput)
pMonthLookupInput.custTime = custPMonthTime
pMonthLookupInput.ZipCode = input.ZipCode
pMonthLookupInput.Country = input.Country
custNMonthTime := input.custTime.AddDate(0, 1, 0)
nMonthLookupInput := new(LookupInput)
nMonthLookupInput.custTime = custNMonthTime
nMonthLookupInput.ZipCode = input.ZipCode
nMonthLookupInput.Country = input.Country
prayerData := AladhanData(input)
pMonthPData := AladhanData(pMonthLookupInput)
nMonthPData := AladhanData(nMonthLookupInput)
// Save prayer data into io.Reader to save to s3
var Marshal = func(data interface{}) (io.ReadSeeker, error) {
mdata, err := json.MarshalIndent(data, "", "t")
if err != nil {
return nil, err
}
return bytes.NewReader(mdata), nil
}
rmData, err := Marshal(prayerData)
pRmData, err := Marshal(pMonthPData)
nRmData, err := Marshal(nMonthPData)
if err != nil {
return nil, err
}
// Save prayer data into s3
g := new(errgroup.Group)
s3Upload := func(rawData *io.ReadSeeker, input *LookupInput) func() error {
return func() error {
s3Client := s3manager.NewUploaderWithClient(awsservices.NewS3Service())
_, err = s3Client.Upload(&s3manager.UploadInput{
Bucket: aws.String(bucket),
Key: aws.String(
fmt.Sprintf(
"%s/%d/%d/%d",
input.Country,
input.ZipCode,
input.custTime.Year(),
int(input.custTime.Month()))),
Body: *rawData,
})
if err != nil {
return err
}
return nil
}
}
g.Go(s3Upload(&pRmData, pMonthLookupInput))
g.Go(s3Upload(&rmData, input))
g.Go(s3Upload(&nRmData, nMonthLookupInput))
if err := g.Wait(); err == nil {
mPrayer.PreviousMonthData = pMonthPData
mPrayer.CurrentMonthData = prayerData
mPrayer.NextMonthData = nMonthPData
return mPrayer, nil
}
return nil, err
}

<代码>

这是我的测试文件。

=== RUN   TestPrayer
loop = 0, data= *prayer.PreCurrNextMonthPrayer <nil>
attempting to retrieve prayer data from s3
err= <nil>
monthlyData= 0xc000131180 &{<nil> 0xc0002612f0 0xc00051e780 0xc00011cea0 []}
loop-return: err == nil 
return monthlyData address & value = 0xc000131180 &{<nil> 0xc0002612f0 0xc00051e780 0xc00011cea0 []}
post-loop:
monthlyData= 0x0 <nil>
return monthlyData address & value = 0x0 <nil>
prayer_test.go:53: Test address: 0x0
prayer_test.go:55: data THIS SHOULDN'T BE NIL: <nil>
prayer_test.go:56: ERROR: %!s(<nil>)
--- PASS: TestPrayer (0.32s)
PASS

这些是我的结果。忽略传递结果，数据首先不是nil，然后是nil。

func NewMonthPrayer(input *LookupInput, prayers ...MonthPrayerIface) (*PreCurrNextMonthPrayer, error) {
var err error
t := &PreCurrNextMonthPrayer{
custData: input,
prayers:  prayers,
}
t, err = t.GetMonthPrayers()
if err != nil {
return nil, err
}
return t, nil
}

Answer 1

重复是由于NewMonthPrayer的GetMonthPrayer调用，这本来就不应该是这样的。它首先被调用，但随后返回，因此覆盖了现有的数据。

// NewPrayer instantiates a prayer type object with the required input
func NewPrayer(input *LookupInput, prayers ...MonthPrayerIface) *Prayer {
return &Prayer{
custData: input,
prayers:  prayers,
}
}

我完全删除了NewMonthPrayer，因为它是不必要的，我还删除了过程中的函数调用，从而解决了最初的问题。

PP_8