小编lab*_*ab0的帖子

我使用github.com/lib/pq将Go与PostgreSQL一起使用。

我想opendb()在其他函数中调用此函数，但是返回值有问题。

 package database

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

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

    func opendb() (*DB) {
            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)

            if err != nil {
                    panic(err)
            }

            defer db.Close()

            return db
    }

如果运行此命令：

$ go run main.go

它将显示此错误：

error:

    undefined: DB

我使用这个库golang.org/x/crypto/bcrypt来散列密码并将散列与密码进行比较，但我遇到了问题，见下文：

main.go 文件

package main

import (
        "./hash"
)

func main() {
        password := "passwd"
        hash := "hhhhhhhhaaaaaaaaaassssssssssshhhhhhhhhhh"

        check := hash.CheckPasswordHash(password, hash)
}

hash/hash.go 文件

package hash

import "golang.org/x/crypto/bcrypt"

func HashPassword(password string) (string, error) {
        bytes, err := bcrypt.GenerateFromPassword([]byte(password), 14)

        return string(bytes), err
}

func CheckPasswordHash(password, hash string) bool {
        err := bcrypt.CompareHashAndPassword([]byte(hash), []byte(password))

        return err == nil
}

如果你运行这个：

$ go run main.go

它会显示这个错误：

./main.go:11:15: hash.CheckPasswordHash undefined（字符串类型没有字段或方法CheckPasswordHash）

为什么这个错误？

当我将结构传递给函数时,我得到错误:期望'struct book'但是参数是'struct book'类型.为什么会这样？

#include <stdio.h>
#include <string.h>

struct book
{
    int id;
    char title[50];
};

int showBooks(struct book x);

int main()
{
    struct book
    {
        int id;
        char title[50];
    };

    struct book book1,book2;

    book1.id = 2;
    book2.id = 3;

    strcpy(book1.title, "c programming");
    strcpy(book2.title, "libc refrence");

    printf("Book\t\tID\n");

    showBooks(book1);
    showBooks(book2);
}

int showBooks(struct book x)
{
    printf("%s\t%d\n", x.title, x.id);
}

错误:

30:12:错误:"showBooks"
showBooks(book1)的参数1的不兼容类型;

10:5:注意:预期的'struct book'但是参数类型为'struct book'int showBooks(struct book x);

31:12:错误:"showBooks"
showBooks(book2)的参数1的不兼容类型;

10:5:注意:预期的'struct book'但是参数类型为'struct book'int showBooks(struct book x);

这里的错误在哪里？