英文:
golang function returns empty slice when slice length more than 700 item
问题
我有一个调用API的函数来获取项目，并将项目返回以与另一个数据库同步。我可以指定返回的项目数量限制。如果限制为700，则返回700个项目。如果超过700个，则返回空切片。
func (d *dataBaseWriterImpl) WriteProducts() error {username := os.Getenv("USERNAME")password := os.Getenv("PASSWORD")// 获取令牌token, err := d.authService.Login(username, password)if err != nil {return err}// 加载产品// 这里的问题是如果数量超过700 <----products, _ := d.scrapperService.LoadProducts(702, 1, token)log.Printf("产品数量 -> %d", len(products)) // 返回的是0 <-----errChan := make(chan error, 2)var cats []models.Categorydb.Conn.Model(&models.Category{}).Find(&cats)var catIds []stringfor _, cat := range cats {catIds = append(catIds, cat.ExternalId)}for _, prod := range products {if d.isValidProduct(catIds, prod.PrimaryVariant.CategoryID) {log.Printf("更新ID -> %v", prod.PrimaryVariant.ID)go d.saveOrUpdateProducts(prod.PrimaryVariant, errChan)} else {log.Printf("不会更新ID -> %v", prod.PrimaryVariant.ID)go func() {errChan <- nil}()}}for range products {err := <-errChanif err != nil {return err}}return nil}
我在返回之前记录了项目的长度，它在LoadProducts实现中返回了实际值。
func (s serviceImpl) LoadProducts(count uint, page uint, token string) ([]models.VariantsResult, error) {jsonBody := []byte(fmt.Sprintf(`{"pageSize": %d, "page": %d, "sortBy": "updatedAt"}`, count, page))body := bytes.NewBuffer(jsonBody)// 创建请求req, err := http.NewRequest("POST", fmt.Sprintf("%v/api/variantGroups/search", os.Getenv("BACKEND")), body)if err != nil {log.Print(err)}// 请求头//req.Header.Add("User-Agent", "Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:84.0) Gecko/20100101 Firefox/84.0")req.Header.Add("Accept", "application/json, text/plain, */*")req.Header.Add("Authorization", fmt.Sprintf("Bearer %v", token))req.Header.Add("Content-Type", "application/json")// 发送请求resp, err := s.client.Do(req)if err != nil {fmt.Println("失败: ", err)}//[]models.Product `json:"data"`// 读取响应type Response struct {Results []models.VariantsResult `json:"results"`Count int `json:"count"`}var response Responseerr = json.NewDecoder(resp.Body).Decode(&response)log.Printf("产品 -> %d", len(response.Results)) // 返回的是实际数量 <--if err != nil {return nil, err}return response.Results, nil}
英文:
I have a function calls API to get items and return items to sync with another db. I can specify limit of items that returns. If the limit is 700 it return 700 item. if more than 700 it return empty slice.
func (d *dataBaseWriterImpl) WriteProducts() error {username := os.Getenv("USERNAME")password := os.Getenv("PASSWORD")// get tokentoken, err := d.authService.Login(username, password)if err != nil {return err}// load products// here the problem if count more than 700 <----products, _ := d.scrapperService.LoadProducts(702, 1, token)log.Printf("products count -> %d", len(products)) // gives me 0 <-----errChan := make(chan error, 2)var cats []models.Categorydb.Conn.Model(&models.Category{}).Find(&cats)var catIds []stringfor _, cat := range cats {catIds = append(catIds, cat.ExternalId)}for _, prod := range products {if d.isValidProduct(catIds, prod.PrimaryVariant.CategoryID) {log.Printf("update id -> %v", prod.PrimaryVariant.ID)go d.saveOrUpdateProducts(prod.PrimaryVariant, errChan)} else {log.Printf("will not update id -> %v", prod.PrimaryVariant.ID)go func() {errChan <- nil}()}}for range products {err := <-errChanif err != nil {return err}}return nil}
I log items length before return it return the actual value in the LoadProducts implementation.
func (s serviceImpl) LoadProducts(count uint, page uint, token string) ([]models.VariantsResult, error) {jsonBody := []byte(fmt.Sprintf(`{"pageSize": %d, "page": %d, "sortBy": "updatedAt"}`, count, page))body := bytes.NewBuffer(jsonBody)// Create requestreq, err := http.NewRequest("POST", fmt.Sprintf("%v/api/variantGroups/search", os.Getenv("BACKEND")), body)if err != nil {log.Print(err)}// Headers//req.Header.Add("User-Agent", "Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:84.0) Gecko/20100101 Firefox/84.0")req.Header.Add("Accept", "application/json, text/plain, */*")req.Header.Add("Authorization", fmt.Sprintf("Bearer %v", token))req.Header.Add("Content-Type", "application/json")// Fetch Requestresp, err := s.client.Do(req)if err != nil {fmt.Println("Failure : ", err)}//[]models.Product `json:"data"`// Read Responsetype Response struct {Results []models.VariantsResult `json:"results"`Count int `json:"count"`}var response Responseerr = json.NewDecoder(resp.Body).Decode(&response)log.Printf("products -> %d", len(response.Results)) // gives me actual number <--if err != nil {return nil, err}return response.Results, nil}
答案1
得分: 3
你几乎可以肯定是返回了一个错误，但是却忽略了它。
> 一个空切片的长度和容量为0，并且没有底层数组。https://tour.golang.org/moretypes/12
你在这里返回了 nil, err：
// 在 LoadProducts 中if err != nil {return nil, err}
但是接下来却这样做了：
products, _ := d.scrapperService.LoadProducts(702, 1, token)log.Printf("products count -> %d", len(products)) // 给我返回了 0 <---
应该改为：
products, err := d.scrapperService.LoadProducts(702, 1, token)if err != nil {panic(err) // 实际上不要恐慌，但要找出出了什么问题}log.Printf("products count -> %d", len(products)) // 给我返回了 0 <---
英文:
Almost certainly you are returning an error, but then ignoring it.
> A nil slice has a length and capacity of 0 and has no underlying array. https://tour.golang.org/moretypes/12
You return nil, err here:
// in LoadProductsif err != nil {return nil, err}
but then do
products, _ := d.scrapperService.LoadProducts(702, 1, token)log.Printf("products count -> %d", len(products)) // gives me 0 <---
which should be
products, err := d.scrapperService.LoadProducts(702, 1, token)if err != nil {panic(err) // dont actually panic, but figure out what went wrong}log.Printf("products count -> %d", len(products)) // gives me 0 <---
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