问题:

I have a struct that I intend to populate with a database record, one of the datetime columns is nullable:

type Reminder struct {
    Id         int
    CreatedAt  time.Time
    RemindedAt *time.Time
    SenderId   int
    ReceiverId int
}

Since pointers can be nil, I've made RemindedAt a pointer, but this will require the code to know the difference between the At variables. Is there a more elegant way to handle this?

回答1:

You can use pq.NullTime.

From lib/pq on github:

type NullTime struct {
    Time  time.Time
    Valid bool // Valid is true if Time is not NULL
}

// Scan implements the Scanner interface.
func (nt *NullTime) Scan(value interface{}) error {
    nt.Time, nt.Valid = value.(time.Time)
    return nil
}

// Value implements the driver Valuer interface.
func (nt NullTime) Value() (driver.Value, error) {
    if !nt.Valid {
        return nil, nil
    }
    return nt.Time, nil
}

回答2:

I like the NullTime example from lib/pq. I tweaked it this way so the NullTime can be treated like a Time...

type NullTime struct {
    time.Time
    Valid bool
}

回答3:

Might also want to check the go-sql-driver implementation, which is basically the same thing as recommended above. https://godoc.org/github.com/go-sql-driver/mysql#NullTime