如何在Golang中的空字符串字段中返回空值？

我有这样的 struct 在Golang应用程序:

type Employee struct {
    ID int `json:"employee_id"`
    Email *string `json:"employee_email"`
    LastName *string `json:"employee_last_name"`
    FirstName *string `json:"employee_first_name"`
    Sex *string `json:"employee_sex"`
}

此结构的某些字符串字段可以为空。 如果我用 *string应用程序返回我"". 如果使用 sql.NullString 它就会返回给我这样的结果:

"employee_last_name": {
    String: "",
    Valid: true
}

我想显示的是字符串字段为空。 null

在文档中我找到了这样的代码:

type NullString struct {
    String string
    Valid  bool
}

func (ns *NullString) Scan(value interface{}) error {
    if value == nil {
        ns.String, ns.Valid = "", false
        return nil
    }
    ns.Valid = true
    return convertAssign(&ns.String, value)
}

func (ns NullString) Value() (driver.Value, error) {
    if !ns.Valid {
        return nil, nil
    }
    return ns.String, nil
}

Edit:

What you want to do is not possible according to the oracle go driver docs:

sql.NullString

sql.NullString is not supported: Oracle DB does not differentiate between an empty string ("") and a NULL

Original Answer:

Need more details on the SQL database type you are connecting to. I know the go SQLite3 pkg - github.com/mattn/go-sqlite3 - supports setting nil for values of type *string.

Check the details of the driver you are using to connect to the database. For instance with MySQL, getting SQL date fields into go's native time.Time struct type is not set by default - it must be turned on at the driver level.

In the Go language specification nil is not a valid value for type string. the default, zero value is "".

The top answer for this question goes into more detail.