Golang中的时间戳

huangapple
go评论118阅读模式
英文:

Timestamps in Golang

问题

尝试让我的应用程序中的时间戳方法起作用：https://gist.github.com/bsphere/8369aca6dde3e7b4392c#file-timestamp-go

这是代码：

  1. package timestamp
  3. import (
  4. 	"fmt"
  5. 	"labix.org/v2/mgo/bson"
  6. 	"strconv"
  7. 	"time"
  8. )
  10. type Timestamp time.Time
  12. func (t *Timestamp) MarshalJSON() ([]byte, error) {
  13. 	ts := time.Time(*t).Unix()
  14. 	stamp := fmt.Sprint(ts)
  16. 	return []byte(stamp), nil
  17. }
  19. func (t *Timestamp) UnmarshalJSON(b []byte) error {
  20. 	ts, err := strconv.Atoi(string(b))
  21. 	if err != nil {
  22. 		return err
  23. 	}
  25. 	*t = Timestamp(time.Unix(int64(ts), 0))
  27. 	return nil
  28. }
  30. func (t Timestamp) GetBSON() (interface{}, error) {
  31. 	if time.Time(*t).IsZero() {
  32. 		return nil, nil
  33. 	}
  35. 	return time.Time(*t), nil
  36. }
  38. func (t *Timestamp) SetBSON(raw bson.Raw) error {
  39. 	var tm time.Time
  41. 	if err := raw.Unmarshal(&tm); err != nil {
  42. 		return err
  43. 	}
  45. 	*t = Timestamp(tm)
  47. 	return nil
  48. }
  50. func (t *Timestamp) String() string {
  51. 	return time.Time(*t).String()
  52. }

以及相关的文章：https://medium.com/coding-and-deploying-in-the-cloud/time-stamps-in-golang-abcaf581b72f

然而，我得到了以下错误：

  1. core/timestamp/timestamp.go:31: invalid indirect of t (type Timestamp)
  2. core/timestamp/timestamp.go:35: invalid indirect of t (type Timestamp)

我的相关代码如下：

  1. import (
  2.     "github.com/path/to/timestamp"
  3. )
  5. type User struct {
  6.     Name        string
  7.     Created_at  *timestamp.Timestamp  `bson:"created_at,omitempty" json:"created_at,omitempty"`
  8. }

有人能看出我做错了什么吗？

相关问题
我也不知道如何使用这个包。我是否需要创建一个新的User模型，类似于这样？

  1. u := User{Name: "Joe Bloggs", Created_at: timestamp.Timestamp(time.Now())}
英文:

Trying to get this approach to timestamps working in my application: https://gist.github.com/bsphere/8369aca6dde3e7b4392c#file-timestamp-go

Here it is:

  1. package timestamp
  3. import (
  4. 	"fmt"
  5. 	"labix.org/v2/mgo/bson"
  6. 	"strconv"
  7. 	"time"
  8. )
  10. type Timestamp time.Time
  12. func (t *Timestamp) MarshalJSON() ([]byte, error) {
  13. 	ts := time.Time(*t).Unix()
  14. 	stamp := fmt.Sprint(ts)
  16. 	return []byte(stamp), nil
  17. }
  19. func (t *Timestamp) UnmarshalJSON(b []byte) error {
  20. 	ts, err := strconv.Atoi(string(b))
  21. 	if err != nil {
  22. 		return err
  23. 	}
  25. 	*t = Timestamp(time.Unix(int64(ts), 0))
  27. 	return nil
  28. }
  30. func (t Timestamp) GetBSON() (interface{}, error) {
  31. 	if time.Time(*t).IsZero() {
  32. 		return nil, nil
  33. 	}
  35. 	return time.Time(*t), nil
  36. }
  38. func (t *Timestamp) SetBSON(raw bson.Raw) error {
  39. 	var tm time.Time
  41. 	if err := raw.Unmarshal(&tm); err != nil {
  42. 		return err
  43. 	}
  45. 	*t = Timestamp(tm)
  47. 	return nil
  48. }
  50. func (t *Timestamp) String() string {
  51. 	return time.Time(*t).String()
  52. }

and the article that goes with it: https://medium.com/coding-and-deploying-in-the-cloud/time-stamps-in-golang-abcaf581b72f

However, I'm getting the following error:

  1. core/timestamp/timestamp.go:31: invalid indirect of t (type Timestamp)                                                                                                                                                     
  2. core/timestamp/timestamp.go:35: invalid indirect of t (type Timestamp)

My relevant code looks like this:

  1. import (
  2.     "github.com/path/to/timestamp"
  3. )
  5. type User struct {
  6.     Name        string
  7.     Created_at  *timestamp.Timestamp  `bson:"created_at,omitempty" json:"created_at,omitempty"`
  8. }

Can anyone see what I'm doing wrong?

Related question
I can't see how to implement this package either. Do I create a new User model something like this?

  1. u := User{Name: "Joe Bloggs", Created_at: timestamp.Timestamp(time.Now())}

答案1

得分: 6

你的代码中有一个拼写错误。你不能对非指针进行解引用，所以你需要将GetBSON方法改为指针接收器（或者你可以删除对t的间接引用，因为方法不会改变t的值）。

  1. func (t *Timestamp) GetBSON() (interface{}, error) {
  2.     // code here
  3. }

要内联设置*Timestamp值，你需要有一个*time.Time来进行转换。

  1. now := time.Now()
  2. u := User{
  3.     Name:      "Bob",
  4.     CreatedAt: (*Timestamp)(&now),
  5. }

构造函数和辅助函数（如New()和Now()）也可能对此有帮助。

英文:

Your code has a typo. You can't dereference a non-pointer, so you need to make GetBSON a pointer receiver (or you could remove the indirects to t, since the value of t isn't changed by the method).

  1. func (t *Timestamp) GetBSON() (interface{}, error) {

To set a *Timestamp value inline, you need to have a *time.Time to convert.

  1. now := time.Now()
  2. u := User{
  3. 	Name:      "Bob",
  4. 	CreatedAt: (*Timestamp)(&now),
  5. }

Constructor and a helper functions like New() and Now() may come in handy for this as well.

答案2

得分: 0

你不能引用一个不是指针变量的间接引用。

  1. var a int = 3         // a = 3
  2. var A *int = &a       // A = 0x10436184
  3. fmt.Println(*A == a)  // true，两者都等于3
  4. fmt.Println(*&a == a) // true，两者都等于3
  5. fmt.Println(*a)       // a的间接引用无效（类型为int）

因此，你不能使用*a引用a的地址。

看一下错误发生的地方：

  1. func (t Timestamp) GetBSON() (interface{}, error) {
  2.         // t是一个变量类型为Timestamp，而不是*Timestamp（指针类型）
  4.         // 因此，除非t是一个指针变量，并且你试图取消引用它以获取Timestamp值，否则这是不可能的
  5.         if time.Time(*t).IsZero() {
  6.                 return nil, nil
  7.         }
  8.         // 这也是如此
  9.         return time.Time(*t), nil
  10. }
英文:

You cannot refer to an indirection of something that is not a pointer variable.

  1. var a int = 3         // a = 3
  2. var A *int = &a       // A = 0x10436184
  3. fmt.Println(*A == a)  // true, both equals 3
  4. fmt.Println(*&a == a) // true, both equals 3
  5. fmt.Println(*a)       // invalid indirect of a (type int)

Thus, you can not reference the address of a with *a.

Looking at where the error happens:

  1. func (t Timestamp) GetBSON() (interface{}, error) {
  2.         // t is a variable type Timestamp, not type *Timestamp (pointer)
  4.         // so this is not possible at all, unless t is a pointer variable
  5.         // and you're trying to dereference it to get the Timestamp value
  6.         if time.Time(*t).IsZero() {
  7.                 return nil, nil
  8.         }
  9.         // so is this
  10.         return time.Time(*t), nil
  11. }

huangapple
  • 本文由 发表于 2015年8月15日 01:11:32
  • 转载请务必保留本文链接：https://go.coder-hub.com/32015364.html
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