database - 如何解决 go 编程语言中的数据库结构问题？

Question

我正在尝试创建 postgresql 数据库结构以在 Golang 中自动化系统。

此代码有效；

package main

import (
    "database/sql"
    "fmt"

    _ "github.com/lib/pq"
)

func checkError(err error){
    if err!=nil{
        panic(err)
    }
}

const (
    host     = "localhost"
    port     = 5432
    user     = "postgres"
    password = "123"
    dbname   = "DatabaseName"
)

func main() {
    psqlInfo := fmt.Sprintf("host=%s port=%d user=%s "+
        "password=%s dbname=%s sslmode=disable",
        host, port, user, password, dbname)
    db, err := sql.Open("postgres", psqlInfo)
    checkError(err)

    err = db.Ping()
    checkError(err)

    defer db.Close()
    fmt.Println("Successfully connected!")
}

Result: Successfully connected!

但是当我试图创建一个结构时，系统给我一个错误；

package main

import (
    "database/sql"
    "fmt"
    _ "github.com/lib/pq"
)

func checkError(err error){
    if err!=nil{
        panic(err)
    }
}

type Database struct{
    host, port, user, password, dbname string
    db *sql.DB
}

func(d *Database) Open(){
    psqlInfo := fmt.Sprintf("host=%s port=%d user=%s "+"password=%s dbname=%s sslmode=disable", d.host, d.port, d.user, d.password, d.dbname)
    db, err := sql.Open("postgres", psqlInfo)
    checkError(err)
    d.db = db
}

func(d *Database) IsOpened() {
    checkError(d.db.Ping())
}

func main() {
    a := Database{host: "localhost", port: "5432", user: "postgres", password: "123", dbname: "DatabaseName"}
    a.Open()
    a.IsOpened()
}

Result: panic: dial tcp: lookup tcp/%!d(string=5432): getaddrinfow: The specified class could not be found.

goroutine 1 [running]: main.checkError(...) /main.go:11

main.(*Database).IsOpened(...) /main.go:28 main.main() /main.go:34 +0xcc

Answer 1

发生这种情况是因为您有数据类型的混搭。您已将端口号声明为字符串，但是在构建连接字符串时，您已将端口号指定为整数，这将生成 host=localhost port=%!d(string=5432) user=postgres password=123 dbname=DatabaseName sslmode=disable 错误的连接字符串。您的连接字符串应该是 host=localhost port=5432 user=postgres password=123 dbname=DatabaseName sslmode=disable。您可以在 struct

中将端口号数据类型从 string 更改为 int

type Database struct {
    host, user, password, dbname string
    port                         int
    db                           *sql.DB
}

https://play.golang.org/p/yP3Y-0NdloQ

或者您可以在构建连接字符串时将端口号类型从%d更改为%s

psqlInfo := fmt.Sprintf("host=%s port=%s user=%s "+"password=%s dbname=%s sslmode=disable", d.host, d.port, d.user, d.password, d.dbname)

https://play.golang.org/p/e61dOUg0MA-