空时间 [英] Nullable time.Time

问题描述

我有一个要用数据库记录填充的结构，其中datetime列之一可以为空:

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
}

由于指针可以是nil，所以我将RemindedAt设置为指针，但这将需要代码知道At变量之间的区别.有没有更优雅的方式来解决这个问题?

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?

推荐答案

您可以使用pq.NullTime，或者在Go 1.13中，现在可以使用标准库的

You can use pq.NullTime, or with Go 1.13, you can now use the standard library's sql.NullTime type.

在github上的 lib/pq 上:

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
}

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