json - 在 golang json.Unmarshal 中处理单个或数组结构的好方法是什么？

Question

我正在使用 Go 和 Yahoo API 构建一个股票报价网络应用程序。

问题是如何在不编写另一个结构的情况下在数组和单个结构之间切换。我不确定如何用语言来解释它。这是示例:

从 Yahoo API 获取一个符号引用如下所示:

{"query":{"count":1,"created":"2016-05-11T02:12:33Z","lang":"en-US","results":{"quote":{"Change":"+0.21","DaysLow":"9.32","DaysHigh":"9.68","Name":"Alcoa Inc. Common Stock","Open":"9.56","PreviousClose":"9.46","Symbol":"aa","Volume":"22266533","PercentChange":"+2.22%"}}}}

从 Yahoo API 获取多个引用:

{"query":{"count":2,"created":"2016-05-11T02:17:48Z","lang":"en-us","results":{"quote":[{"Change":"+0.21","DaysLow":"9.32","DaysHigh":"9.68","Name":"Alcoa Inc. Common Stock","Open":"9.56","PreviousClose":"9.46","Symbol":"aa","Volume":"22266533","PercentChange":"+2.22%"},{"Change":"+0.63","DaysLow":"92.11","DaysHigh":"93.57","Name":"Apple Inc.","Open":"93.35","PreviousClose":"92.79","Symbol":"aapl","Volume":"33686836","PercentChange":"+0.68%"}]}}}

区别在于引号变成了数组[]。

使用json.Unmarshal(quoteResultRawJSON, &queryResult)时如何处理？

我的结构看起来像:

type QueryResult struct {
  Id bson.ObjectId `bson:"_id,omitempty"`
  Query Query `json:"query"`
}

type Query struct {
  Count int `json:"count"`
  Created string `json:"created"`
  Lang string `json:"lang"`
  Results Quote `json:"results"`
}

type Quote struct {
  Quote StockQuote `json:"quote"` //Here is the difference. Do I need to re-write the whole struct in order to handle []
}

type StockQuote struct {
  Change string `json:"change"`
  PercentChange string `json:"percentChange"`
  DaysLow string `json:"daysLow"`
  DaysHigh string `json:"daysHigh"`
  Open string `json:"open"`
  PreviousClose string `json:"previousClose"`
  Symbol string `json:"symbol"`
  Name string `json:"name"`
  Volume string `json:"volume"`
 }

我是否必须编写另一个结构来处理数组？

Answer 1

使用 UnmarshalJSON() 覆盖控制解码过程。

https://play.golang.org/p/pCSgymQYC3

package main

import (
    "log"
    "encoding/json"
    "bytes"
)

const(
    s1=`{"query":{"count":1,"created":"2016-05-11T02:12:33Z","lang":"en-US","results":{"quote":{"Change":"+0.21","DaysLow":"9.32","DaysHigh":"9.68","Name":"Alcoa Inc. Common Stock","Open":"9.56","PreviousClose":"9.46","Symbol":"aa","Volume":"22266533","PercentChange":"+2.22%"}}}}`
    s2=`{"query":{"count":2,"created":"2016-05-11T02:17:48Z","lang":"en-us","results":{"quote":[{"Change":"+0.21","DaysLow":"9.32","DaysHigh":"9.68","Name":"Alcoa Inc. Common Stock","Open":"9.56","PreviousClose":"9.46","Symbol":"aa","Volume":"22266533","PercentChange":"+2.22%"},{"Change":"+0.63","DaysLow":"92.11","DaysHigh":"93.57","Name":"Apple Inc.","Open":"93.35","PreviousClose":"92.79","Symbol":"aapl","Volume":"33686836","PercentChange":"+0.68%"}]}}}`
)
type QueryResult struct {
    //Id bson.ObjectId `bson:"_id,omitempty"`
    Query Query `json:"query"`
}

type Query struct {
    Count int `json:"count"`
    Created string `json:"created"`
    Lang string `json:"lang"`
    Results Quote `json:"results"`
}

type structOrArray struct{
    parent *Quote
    s StockQuote
    a []StockQuote
}

func (this *structOrArray)UnmarshalJSON(data []byte) error{
    d := json.NewDecoder(bytes.NewBuffer(data))
    t, err := d.Token();
    if err != nil{
        return err
    }
    if t==json.Delim('['){
        if err := json.Unmarshal(data, &this.a);err != nil {
            return err
        }
        return nil
    }
    if err := json.Unmarshal(data, &this.s);err != nil {
        return err
    }
    return nil
}

type fakeQuote struct{
    Load structOrArray `json:"quote"` //Here is the difference. Do I need to re-write the whole struct in order to handle []
}
type Quote struct {
    Quote *StockQuote
    Quotes []StockQuote
}
func (this *Quote)UnmarshalJSON(data []byte) error{
    fq := fakeQuote{}
    if err := json.Unmarshal(data, &fq);err != nil{
        return err
    }
    this.Quote = &fq.Load.s
    this.Quotes = fq.Load.a
    return nil
}
type StockQuote struct {
    Change string `json:"change"`
    PercentChange string `json:"percentChange"`
    DaysLow string `json:"daysLow"`
    DaysHigh string `json:"daysHigh"`
    Open string `json:"open"`
    PreviousClose string `json:"previousClose"`
    Symbol string `json:"symbol"`
    Name string `json:"name"`
    Volume string `json:"volume"`
}
func main() {
    r := QueryResult{}
    err := json.Unmarshal([]byte(s1), &r)
    if err != nil {
        log.Fatalln(err)
    }
    log.Println(r.Query.Results.Quote)
    log.Println(r.Query.Results.Quotes)

    err = json.Unmarshal([]byte(s2), &r)
    if err != nil {
        log.Fatalln(err)
    }
    log.Println(r.Query.Results.Quote)
    log.Println(r.Query.Results.Quotes)
}