当我尝试使用`db.QueryRow`时，出现了Golang运行时错误。

huangapple
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英文:

golang runtime error when i am trying to use db.QueryRow

问题

我有一个controller.go文件：

  1. package controller
  3. import (
  4.     "github.com/fishkaoff/todoList/pkg/postgresql"
  5.     "github.com/gin-gonic/gin"
  6.     "net/http"
  7.     "context"
  8. )
  10. type Task struct {
  11.     Title       string
  12.     Description string
  13. }
  15. func GetTasks(c *gin.Context) {
  16.     var response *Task
  17.     err := db.Conn.QueryRow(context.Background(), "select * from tasks").Scan(&response.Title, &response.Description)
  18.     if err != nil {
  19.         c.JSON(http.StatusInternalServerError, gin.H{"error": "error"})
  20.     }
  22.     c.JSON(200, gin.H{
  23.         "page":  "gettasks",
  24.         "tasks": response,
  25.     })
  26. }

当我发送请求时，它返回以下错误信息：

  1. runtime error: invalid memory address or nil pointer dereference
  2. C:/Program Files/Go/src/runtime/panic.go:260 (0xb7bab5)
  3.         panicmem: panic(memoryError)
  4. C:/Program Files/Go/src/runtime/signal_windows.go:255 (0xb7ba85)
  5.         sigpanic: panicmem()
  6. D:/workspace/golangWWW/pkg/mod/github.com/jackc/pgx/v4@v4.17.2/conn.go:551 (0x1015db1)
  7.         (*Conn).Query: simpleProtocol := c.config.PreferSimpleProtocol
  8. D:/workspace/golangWWW/pkg/mod/github.com/jackc/pgx/v4@v4.17.2/conn.go:663 (0x101b9dc)
  9.         (*Conn).QueryRow: rows, _ := c.Query(ctx, sql, args...)
  10. D:/workspace/golangWWW/todolist/internal/controller/controller.go:17 (0x101b9ab)
  11.         GetTasks: err := db.Conn.QueryRow(context.Background(), "select * from tasks").Scan(&response.Title, &response.Description)
  12. D:/workspace/golangWWW/pkg/mod/github.com/gin-gonic/gin@v1.8.1/context.go:173 (0xeb99c1)
  13.         (*Context).Next: c.handlers[c.index](c)
  14. D:/workspace/golangWWW/pkg/mod/github.com/gin-gonic/gin@v1.8.1/recovery.go:101 (0xeb99ac)
  15.         CustomRecoveryWithWriter.func1: c.Next()
  16. D:/workspace/golangWWW/pkg/mod/github.com/gin-gonic/gin@v1.8.1/context.go:173 (0xeb8ac6)
  17.         (*Context).Next: c.handlers[c.index](c)
  18. D:/workspace/golangWWW/pkg/mod/github.com/gin-gonic/gin@v1.8.1/logger.go:240 (0xeb8aa9)
  19.         LoggerWithConfig.func1: c.Next()
  20. D:/workspace/golangWWW/pkg/mod/github.com/gin-gonic/gin@v1.8.1/context.go:173 (0xeb7bd0)
  21.         (*Context).Next: c.handlers[c.index](c)
  22. D:/workspace/golangWWW/pkg/mod/github.com/gin-gonic/gin@v1.8.1/gin.go:616 (0xeb7838)
  23.         (*Engine).handleHTTPRequest: c.Next()
  24. D:/workspace/golangWWW/pkg/mod/github.com/gin-gonic/gin@v1.8.1/gin.go:572 (0xeb74fc)
  25.         (*Engine).ServeHTTP: engine.handleHTTPRequest(c)
  26. C:/Program Files/Go/src/net/http/server.go:2947 (0xd70feb)
  27.         serverHandler.ServeHTTP: handler.ServeHTTP(rw, req)
  28. C:/Program Files/Go/src/net/http/server.go:1991 (0xd6d6c6)
  29.         (*conn).serve: serverHandler{c.server}.ServeHTTP(w, w.req)
  30. C:/Program Files/Go/src/runtime/asm_amd64.s:1594 (0xb96320)
  31.         goexit: BYTE    $0x90   // NOP

db.Conn是从db.go导入的：

  1. package db
  3. import (
  4.     "os"
  5.     "fmt"
  6.     "context"
  8.     "github.com/jackc/pgx/v4/"
  9.     "github.com/fishkaoff/todoList/internal/config"
  10. )
  12. var Conn *pgx.Conn
  14. func InitDatabase(config config.Config) {
  15.     Conn, err := pgx.Connect(context.Background(), config.DBUrl)
  16.     if err != nil {
  17.         fmt.Fprintf(os.Stderr, "Unable to connect to database: %v\n", err)
  18.         os.Exit(1)
  19.     }
  20.     defer Conn.Close()
  21. }

InitDatabase在main.go中调用。

数据库表和列已创建。

我正在使用pgx v4版本。

P.S：对于我的糟糕英语表示抱歉，我不是以英语为母语的人。

英文:

i have controller.go:

  1. package controller
  2. import (
  3.     "github.com/fishkaoff/todoList/pkg/postgresql"
  4.     "github.com/gin-gonic/gin"
  5.     "net/http"
  6.     "context"
  7. )
  9. type Task struct {
  10.     Title string 
  11.     Description string
  12.  }
  15. func GetTasks(c *gin.Context) {
  16.     var response *Task
  17.     err := db.Conn.QueryRow(context.Background(), "select * from tasks").Scan(&response.Title, 
  18.     &response.Description)
  19.     if err != nil {
  20. 	    c.JSON(http.StatusInternalServerError, gin.H{"error":"error"})
  21.     }
  23.     c.JSON(200, gin.H{
  24. 	    "page":"gettasks",
  25. 	    "tasks": response,
  26.     })
  27. }

when i am sending request it returns me

  1. ```runtime error: invalid memory address or nil pointer dereference
  2. C:/Program Files/Go/src/runtime/panic.go:260 (0xb7bab5)
  3.         panicmem: panic(memoryError)
  4. C:/Program Files/Go/src/runtime/signal_windows.go:255 (0xb7ba85)
  5.         sigpanic: panicmem()
  6. D:/workspace/golangWWW/pkg/mod/github.com/jackc/pgx/v4@v4.17.2/conn.go:551 (0x1015db1)
  7.         (*Conn).Query: simpleProtocol := c.config.PreferSimpleProtocol
  8. D:/workspace/golangWWW/pkg/mod/github.com/jackc/pgx/v4@v4.17.2/conn.go:663 (0x101b9dc)
  9.         (*Conn).QueryRow: rows, _ := c.Query(ctx, sql, args...)
  10. D:/workspace/golangWWW/todolist/internal/controller/controller.go:17 (0x101b9ab)
  11.         GetTasks: err := db.Conn.QueryRow(context.Background(), "select * from tasks").Scan(&response.Title, &response.Description)
  12. D:/workspace/golangWWW/pkg/mod/github.com/gin-gonic/gin@v1.8.1/context.go:173 (0xeb99c1)
  13.         (*Context).Next: c.handlers[c.index](c)
  14. D:/workspace/golangWWW/pkg/mod/github.com/gin-gonic/gin@v1.8.1/recovery.go:101 (0xeb99ac)
  15.         CustomRecoveryWithWriter.func1: c.Next()
  16. D:/workspace/golangWWW/pkg/mod/github.com/gin-gonic/gin@v1.8.1/context.go:173 (0xeb8ac6)
  17.         (*Context).Next: c.handlers[c.index](c)
  18. D:/workspace/golangWWW/pkg/mod/github.com/gin-gonic/gin@v1.8.1/logger.go:240 (0xeb8aa9)
  19.         LoggerWithConfig.func1: c.Next()
  20. D:/workspace/golangWWW/pkg/mod/github.com/gin-gonic/gin@v1.8.1/context.go:173 (0xeb7bd0)
  21.         (*Context).Next: c.handlers[c.index](c)
  22. D:/workspace/golangWWW/pkg/mod/github.com/gin-gonic/gin@v1.8.1/gin.go:616 (0xeb7838)
  23.         (*Engine).handleHTTPRequest: c.Next()
  24. D:/workspace/golangWWW/pkg/mod/github.com/gin-gonic/gin@v1.8.1/gin.go:572 (0xeb74fc)
  25.         (*Engine).ServeHTTP: engine.handleHTTPRequest(c)
  26. C:/Program Files/Go/src/net/http/server.go:2947 (0xd70feb)
  27.         serverHandler.ServeHTTP: handler.ServeHTTP(rw, req)
  28. C:/Program Files/Go/src/net/http/server.go:1991 (0xd6d6c6)
  29.         (*conn).serve: serverHandler{c.server}.ServeHTTP(w, w.req)
  30. C:/Program Files/Go/src/runtime/asm_amd64.s:1594 (0xb96320)
  31.         goexit: BYTE    $0x90   // NOP```

db.Conn is imported from db.go:

  1.     package db
  4.     import (
  5. 	    "os"
  6. 	    "fmt"
  7. 	    "context"
  10. 	    "github.com/jackc/pgx/v4/"
  11. 	    "github.com/fishkaoff/todoList/internal/config"
  12.     )
  14.     var Conn *pgx.Conn
  16.     func InitDatabase(config config.Config) {
  17. 	    Conn, err := pgx.Connect(context.Background(), config.DBUrl)
  18. 	    if err != nil {
  19. 		    fmt.Fprintf(os.Stderr, "Unable to connect to database: %v\n", err)
  20. 		    os.Exit(1)
  21. 	    }
  22. 	    defer Conn.Close()
  23.     }

InitDatabase is calling in main.go

in database table and columns are created

i am using pgx v4

P.S: sorry for my bad english, i am not a native speaker
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答案1

得分: 2

你已经分配了内存来存储 *Task，而不是 Task。

然后当你尝试获取 response.Title 和 response.Description 的地址时，这些字段没有地址，因为 response 是一个指针，但没有指向有效的任务。

尝试使用以下代码：

  1. var response Task

现在你实际上已经为 Title 和 Description 字段分配了空间，因此有地方来存储这些值。

英文: 
  1.     var response *Task

You have allocated memory to store a *Task, not a Task.

Then when you

  1.     .Scan(&response.Title,     &response.Description)

Attempt to take the address of response.Title and response.Description. These fields don't have an address because response is a pointer but doesn't point to a valid task.

Try:

  1. var response Task

Now you actually have allocated space for the Title and Description fields and thus have somewhere to store those values.

huangapple
  • 本文由 发表于 2022年9月17日 22:16:33
  • 转载请务必保留本文链接：https://go.coder-hub.com/73755591.html
  • database
  • go
  • pgx
  • postgresql
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