如何正确地反序列化不同类型的数组?

huangapple go评论95阅读模式
英文:

How to unmarshall an array of different types correctly?

问题

只要我有键值对,解组就很简单,但是如何解组一个不同类型的数组并且顺序不同呢?单个元素是明确定义和已知的,但是顺序不确定。

我想不出一个优雅的解决方案。

我应该尝试所有元素吗?
是否有一种可以为我做到这一点的联合类型?

playground版本

package main

import (
    "encoding/json"
    "fmt"
)

var my_json string = `{
    "an_array":[
        "with_a string",
        {
            "and":"some_more",
            "different":["nested", "types"]
        }
    ]
}`

type MyInner struct {
    And     string
    Different   []string
}

type MyJSON struct {
    An_array []json.RawMessage
}

func main() {
    var my_json_test MyJSON

    e := json.Unmarshal([]byte(my_json), &my_json_test)
    if e != nil {
        fmt.Println(e)
    } else {
        for index, value := range my_json_test.An_array {
            fmt.Println("index: ", index)
            fmt.Println("value: ", string(value))
        }
        var my_inner MyInner
        err := json.Unmarshal(my_json_test.An_array[1], &my_inner)
        if err != nil {
            fmt.Println(err)
        } else {
            fmt.Println("inner structure: ", my_inner)
        }
    }
}
英文:

As long as I have key-value pairs unmarshalling is pretty straight forward but how would I unmarshall an array of different types in different order? The single elements are well defined and known but the order is not.

I can not come up with a beautiful solution.

Would I try and error over all elements?
Is there some kind of union type that could do that for me?

playground version

package main

import (
    "encoding/json"
    "fmt"
)

var my_json string = `{
    "an_array":[
        "with_a string",
        {
            "and":"some_more",
            "different":["nested", "types"]
        }
    ]
}`

type MyInner struct {
    And     string
    Different   []string
}

type MyJSON struct {
    An_array []json.RawMessage
}

func main() {
    var my_json_test MyJSON

    e := json.Unmarshal([]byte(my_json), &my_json_test)
    if e != nil {
        fmt.Println(e)
    } else {
        for index, value := range my_json_test.An_array {
            fmt.Println("index: ", index)
            fmt.Println("value: ", string(value))
        }
        var my_inner MyInner
        err := json.Unmarshal(my_json_test.An_array[1], &my_inner)
        if err != nil {
            fmt.Println(err)
        } else {
            fmt.Println("inner structure: ", my_inner)
        }
    }
}

答案1

得分: 22

Go官方博客有一篇关于encoding/json的好文章:JSON和GO。可以将任意数据解码为interface{},并使用类型断言来动态确定类型。

你的代码可以修改为以下形式:

package main

import (
    "encoding/json"
    "fmt"
)

var my_json string = `{
    "an_array":[
    "with_a string",
    {
        "and":"some_more",
        "different":["nested", "types"]
    }
    ]
}`

func WTHisThisJSON(f interface{}) {
    switch vf := f.(type) {
    case map[string]interface{}:
        fmt.Println("是一个map:")
        for k, v := range vf {
            switch vv := v.(type) {
            case string:
                fmt.Printf("%v: 是字符串 - %q\n", k, vv)
            case int:
                fmt.Printf("%v: 是整数 - %q\n", k, vv)
            default:
                fmt.Printf("%v: ", k)
                WTHisThisJSON(v)
            }

        }
    case []interface{}:
        fmt.Println("是一个数组:")
        for k, v := range vf {
            switch vv := v.(type) {
            case string:
                fmt.Printf("%v: 是字符串 - %q\n", k, vv)
            case int:
                fmt.Printf("%v: 是整数 - %q\n", k, vv)
            default:
                fmt.Printf("%v: ", k)
                WTHisThisJSON(v)
            }

        }
    }
}

func main() {

    fmt.Println("JSON:\n", my_json, "\n")

    var f interface{}
    err := json.Unmarshal([]byte(my_json), &f)
    if err != nil {
        fmt.Println(err)
    } else {
        fmt.Printf("JSON: ")
        WTHisThisJSON(f)
    }
}

它的输出如下:

JSON:
 {
    "an_array":[
    "with_a string",
    {
        "and":"some_more",
        "different":["nested", "types"]
    }
    ]
} 

JSON: 是一个map:
an_array: 是一个数组:
0: 是字符串 - "with_a string"
1: 是一个map:
and: 是字符串 - "some_more"
different: 是一个数组:
0: 是字符串 - "nested"
1: 是字符串 - "types"

它还不完整,但展示了它将如何工作。

英文:

Go official blog has a nice article about encoding/json: JSON and GO. It's possible to "Decode arbitrary data" into an interface{} and use type assertion to determine the type dynamically.

Your code can be probably modified to this:

package main

import (
    "encoding/json"
    "fmt"
)

var my_json string = `{
    "an_array":[
    "with_a string",
    {
        "and":"some_more",
        "different":["nested", "types"]
    }
    ]
}`

func WTHisThisJSON(f interface{}) {
    switch vf := f.(type) {
    case map[string]interface{}:
        fmt.Println("is a map:")
        for k, v := range vf {
            switch vv := v.(type) {
            case string:
                fmt.Printf("%v: is string - %q\n", k, vv)
            case int:
                fmt.Printf("%v: is int - %q\n", k, vv)
            default:
                fmt.Printf("%v: ", k)
                WTHisThisJSON(v)
            }

        }
    case []interface{}:
        fmt.Println("is an array:")
        for k, v := range vf {
            switch vv := v.(type) {
            case string:
                fmt.Printf("%v: is string - %q\n", k, vv)
            case int:
                fmt.Printf("%v: is int - %q\n", k, vv)
            default:
                fmt.Printf("%v: ", k)
                WTHisThisJSON(v)
            }

        }
    }
}

func main() {

    fmt.Println("JSON:\n", my_json, "\n")

    var f interface{}
    err := json.Unmarshal([]byte(my_json), &f)
    if err != nil {
        fmt.Println(err)
    } else {
        fmt.Printf("JSON: ")
        WTHisThisJSON(f)
    }
}

It gives output as follows:

JSON:
 {
    "an_array":[
    "with_a string",
    {
        "and":"some_more",
        "different":["nested", "types"]
    }
    ]
} 

JSON: is a map:
an_array: is an array:
0: is string - "with_a string"
1: is a map:
and: is string - "some_more"
different: is an array:
0: is string - "nested"
1: is string - "types"

It's not complete yet, but shows how it's gonna work.

huangapple
  • 本文由 发表于 2012年11月14日 00:02:46
  • 转载请务必保留本文链接:https://go.coder-hub.com/13364181.html
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