Question

我有一些JSON可以有一个数字或一个字符串作为第一个元素。我总是希望能够将其存储为字符串值，但我得到了一个崩溃，因为它正确地读取它是一个数字类型。

我试图将解组强制为字符串，但这并不成功。

string `json:",string"`

我正在关注此guide，这似乎很适合我的数据。

如何始终在[0]处获取此元素以始终读取并保存为字符串？

代码＆amp;下面的游乐场......

https://play.golang.org/p/KP4_1xPJiZ

package main

import "fmt"
import "log"
import "encoding/json"

const inputWorking = `
["AAAAAA", {"testcode" : "Sss"}, 66666666]
`

const inputBroken = `
[111111, {"testcode" : "Sss"}, 66666666]
`

type RawMessage struct {
    AlwaysString        string `json:",string"`
    ClientData    ClientData
    ReceptionTime int
}

type ClientData struct {
    testcode string
}

func main() {

    var n RawMessage
    if err := json.Unmarshal([]byte(inputWorking), &n); err != nil {
        log.Fatal(err)
    }

    fmt.Printf("%#v\n", n)

    var o RawMessage
    if err := json.Unmarshal([]byte(inputBroken), &o); err != nil {
        log.Fatal(err)
    }

    fmt.Printf("%#v\n", o)
}

func (n *RawMessage) UnmarshalJSON(buf []byte) error {
    tmp := []interface{}{&n.AlwaysString, &n.ClientData, &n.ReceptionTime}
    wantLen := len(tmp)
    if err := json.Unmarshal(buf, &tmp); err != nil {
        return err
    }
    if g, e := len(tmp), wantLen; g != e {
        return fmt.Errorf("wrong number of fields in RawMessage: %d != %d", g, e)
    }
    return nil
}

Answer 1

您可以创建通用接收器，即接口类型，然后执行类型断言：

package main

import (
    "encoding/json"
    "fmt"
)

type RawMessage struct {
    UnknownType interface{} `json:"unknown_type"`
}

const inputString = `{"unknown_type" : "a"}`

const inputFloat = `{"unknown_type" : 123}` // Note: Unmarshals into a float64 by default!!!

func main() {

    var n RawMessage
    if err := json.Unmarshal([]byte(inputFloat), &n); err != nil {
        println(err.Error())
    }

    switch v := n.UnknownType.(type) {
    case string:
        fmt.Printf("Received a string: %v", v)
    case float64:
        fmt.Printf("Received a number: %v", v)
    default:
        fmt.Printf("Unknown type: %v", v)
    }
}

Answer 2

我遇到了同样的问题，到目前为止，我发现最好的是使用自定义unmarshaller从字符串创建一个类型：

package main

import (
    "encoding/json"
    "fmt"
    "strconv"
)

// Stringish exists because api send back integers unquoted even if underlying type is string
type StringIsh string

func (f *StringIsh) UnmarshalJSON(data []byte) error {

    var receiver string
    if len(data) == 0 {
        return nil
    }
    if data[0] != '"' {
        quoted := strconv.Quote(string(data))
        data = []byte(quoted)
    }

    if err := json.Unmarshal(data, &receiver); err != nil {
        return err
    }
    *f = StringIsh(receiver)
    return nil

}

type Test struct {
    Foo StringIsh
}

func main() {
    dest := &Test{}
    _ = json.Unmarshal([]byte(`{"foo": "bar"}`), &dest)
    fmt.Println(dest)

    dest = &Test{}
    _ = json.Unmarshal([]byte(`{"foo": 123}`), &dest)
    fmt.Println(dest)
}

在https://goplay.space/#i0OVs9tnule

处自行尝试

Answer 3

如果解决此问题，请尝试此操作，在未定义用户输入的情况下创建通用接口

rake assets:precompile production --trace
** Invoke assets:precompile (first_time)
** Invoke assets:environment (first_time)
** Execute assets:environment
** Invoke environment (first_time)
** Execute environment
** Execute assets:precompile
rake aborted!
Don't know how to build task 'production' (see --tasks)
/usr/local/rvm/gems/ruby-2.3.1/gems/rake-11.3.0/lib/rake/task_manager.rb:71:in `[]'
/usr/local/rvm/gems/ruby-2.3.1/gems/rake-11.3.0/lib/rake/application.rb:151:in `invoke_task'
/usr/local/rvm/gems/ruby-2.3.1/gems/rake-11.3.0/lib/rake/application.rb:108:in `block (2 levels) in top_level'
/usr/local/rvm/gems/ruby-2.3.1/gems/rake-11.3.0/lib/rake/application.rb:108:in `each'
/usr/local/rvm/gems/ruby-2.3.1/gems/rake-11.3.0/lib/rake/application.rb:108:in `block in top_level'
/usr/local/rvm/gems/ruby-2.3.1/gems/rake-11.3.0/lib/rake/application.rb:117:in `run_with_threads'
/usr/local/rvm/gems/ruby-2.3.1/gems/rake-11.3.0/lib/rake/application.rb:102:in `top_level'
/usr/local/rvm/gems/ruby-2.3.1/gems/rake-11.3.0/lib/rake/application.rb:80:in `block in run'
/usr/local/rvm/gems/ruby-2.3.1/gems/rake-11.3.0/lib/rake/application.rb:178:in `standard_exception_handling'
/usr/local/rvm/gems/ruby-2.3.1/gems/rake-11.3.0/lib/rake/application.rb:77:in `run'
/usr/local/rvm/gems/ruby-2.3.1/gems/rake-11.3.0/exe/rake:27:in `<top (required)>'
/usr/local/rvm/gems/ruby-2.3.1/bin/rake:23:in `load'
/usr/local/rvm/gems/ruby-2.3.1/bin/rake:23:in `<main>'

package main

interface{} `json:",string"`

将JSON解组为特定类型（字符串）总是

3 个答案: