go之多个数据库驱动程序场景 : passing interface as type

场景:我有一个数据库类型实现了一些 CRUD 操作。

我想:

cannot use dbdriver (variable of type interface{}) as database value in struct literal: missing method GetUser

package main 
 
import "fmt" 
 
type database interface { 
    GetUser(string) 
} 
 
type postgres struct { 
    hostname string 
} 
 
func (p *postgres) GetUser(u string) { 
    fmt.Printf("Postgres: GetUser %s\n", u) 
} 
 
type cache struct { 
    db database 
} 
 
func cacheNew(dbdriver interface{}) cache { 
    return cache{ 
        db: dbdriver, 
    } 
} 
 
func (c *cache) GetUser(u string) { 
    fmt.Printf("Cache: GetUser %s\n", u) 
 
    c.db.GetUser(u) 
} 
 
func main() { 
    // var db database 
 
    db := postgres{ 
        hostname: "x", 
    } 
    db.GetUser("joe") 
 
    dbViaCache := cacheNew(db) 
    dbViaCache.GetUser("joe") 
} 

请您参考如下方法:

为了解决您的问题，添加 newPostgres 构造函数。下面我对您的初始代码进行了更正。

package main 
 
import "fmt" 
 
type database interface { 
    GetUser(string) 
} 
 
type postgres struct { 
    hostname string 
} 
 
func newPostgres(hostname string) *postgres { 
    return &postgres{ 
        hostname: hostname, 
    } 
} 
 
func (p *postgres) GetUser(u string) { 
    fmt.Printf("Postgres: GetUser %s\n", u) 
} 
 
type cache struct { 
    db database 
} 
 
func cacheNew(db database) cache { 
    return cache{ 
        db: db, 
    } 
} 
 
func (c *cache) GetUser(u string) { 
    fmt.Printf("Cache: GetUser %s\n", u) 
 
    c.db.GetUser(u) 
} 
 
func main() { 
    db := newPostgres("x") 
 
    db.GetUser("joe") 
 
    dbViaCache := cacheNew(db) 
    dbViaCache.GetUser("joe") 
}