无法将对象传递给Typescript中的构造函数

我在Typescript中有一个对象MYSQLCredentials，它保存登录MySQL数据库的凭据，该数据库被发送到MySQL对象的构造函数中，该对象实例化与MySQL服务器的连接。我无法使构造函数从凭据对象读取属性

//MySQL connection instantiation object
constructor(cred:MySQLCredentials){
        this.mysqlConnection = mysql.createConnection({
            host     : cred.getHost(), //This is the line with the error
            user     : cred.getUser(),
            password : cred.getPassword()
        });
}

//Credentials object
export class MySQLCredentials implements Credentials{

    host:string;
    user:string;
    password:string;

    constructor(host:string, user:string, password:string){
        console.log("STARTING SQL");
        this.host = host;
        this.user = user;
        this.password = password;
    }

    public getHost():string{
        return this.host;
    }

    public getUser():string{
        return this.user;
    }

    public getPassword():string{
        return this.password;
    }
}

//Error: TypeError: Cannot call method 'getHost' of undefined

以下是运行时：

var credentials = mysqlCredentials.MySQLCredentials('192.168.249.139', 'dev', 'dev');
var sqlConnector = new mysql.Mysql(credentials);

---

您刚刚错过了一个要实例化一个新的

MySQLCredentials

类的

new

：

var credentials = new mysqlCredentials.MySQLCredentials('192.168.249.139', 'dev', 'dev');

---

这意味着在运行时，您传递的是

undefined

，而不是

MySQLCredentials

@Anzeo的实例。我已经更新了问题以显示上述运行时