dongyi9330
dongyi9330
采纳率100%
2019-02-10 16:42

将时间“””解析为“ 2006-01-02T15:04:05Z07:00”:无法将“”解析为“ 2006”

已采纳

我正在尝试将一些json解组到结构中,出现以下内容:

package main

import (
    "encoding/json"
    "fmt"
    "strings"
    "time"
)

type Added struct {
    Added *time.Time `json:"added"`
}

func main() {
    st := strings.NewReader(`{"added": ""}`)

    a := &Added{}
    err := json.NewDecoder(st).Decode(&a)
    if err != nil {
        panic(err)
    }

    fmt.Println(a)

}

运行以上结果将导致:

panic: parsing time """" as ""2006-01-02T15:04:05Z07:00"": cannot parse """ as "2006"

于是我尝试一个自定义编组器:

package main

import (
    "encoding/json"
    "fmt"
    "strings"
    "time"
)

type Added struct {
    Added *MyTime `json:"added"`
}

func main() {
    st := strings.NewReader(`{"added": ""}`)

    a := &Added{}
    err := json.NewDecoder(st).Decode(&a)
    if err != nil {
        panic(err)
    }

    fmt.Println(a)

}

type MyTime struct {
    *time.Time
}

func (m *MyTime) UnmarshalJSON(data []byte) error {
    // Ignore null, like in the main JSON package.
    if string(data) == "null" || string(data) == `""` {
        return nil
    }
    // Fractional seconds are handled implicitly by Parse.
    tt, err := time.Parse(`"`+time.RFC3339+`"`, string(data))
    *m = MyTime{&tt}
    return err
}

然后我得到:

&{%!v(PANIC=runtime error: invalid memory address or nil pointer dereference)}

那现在我该怎么办? 我只想处理json中的“”值.

并能够找到带有完整示例的游乐场。

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2条回答

  • dsgk0386 dsgk0386 2年前

    Package time

    import "time"

    type Time

    A Time represents an instant in time with nanosecond precision.

    Programs using times should typically store and pass them as values, not pointers. That is, time variables and struct fields should be of type time.Time, not *time.Time.


    I just kept fixing likely problems, for example, time.Time, not *time.Time, a real date, and so on, until I got a reasonable result:

    package main
    
    import (
        "encoding/json"
        "fmt"
        "strings"
        "time"
    )
    
    type MyTime struct {
        time.Time
    }
    
    func (m *MyTime) UnmarshalJSON(data []byte) error {
        // Ignore null, like in the main JSON package.
        if string(data) == "null" || string(data) == `""` {
            return nil
        }
        // Fractional seconds are handled implicitly by Parse.
        tt, err := time.Parse(`"`+time.RFC3339+`"`, string(data))
        *m = MyTime{tt}
        return err
    }
    
    type Added struct {
        Added MyTime `json:"added"`
    }
    
    func main() {
        st := strings.NewReader(`{"added": "2012-04-23T18:25:43.511Z"}`)
    
        var a Added
        err := json.NewDecoder(st).Decode(&a)
        if err != nil {
            panic(err)
        }
        fmt.Println(a)
    }
    

    Playground: https://play.golang.org/p/Uusdp3DkXDU

    Output:

    {2012-04-23 18:25:43.511 +0000 UTC}
    

    With an empty ("") date string, the time.Time zero value, 0001-01-01 00:00:00 +0000 UTC:

    Playground: https://play.golang.org/p/eQoEyqBlhg2

    Output:

    {0001-01-01 00:00:00 +0000 UTC}
    

    Use the time IsZero method to test for the zero value.

    func (Time) IsZero

    func (t Time) IsZero() bool
    

    IsZero reports whether t represents the zero time instant, January 1, year 1, 00:00:00 UTC.

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  • dongsu1951 dongsu1951 2年前

    I think you were very close to the solution with your custom marshaller. Maybe just revert to normal decoding for normal dates. This may help:

    type MyTime time.Time
    
    func (m *MyTime) UnmarshalJSON(data []byte) error {
        // Ignore null, like in the main JSON package.
        if string(data) == "null" || string(data) == `""` {
            return nil
        }
        return json.Unmarshal(data, (*time.Time)(m))
    }
    
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