解組動態JSON

Question

我收到遵循這種模式的API動態JSON：

{ 
    "ts": timestamp, 
    "data": [ 
     [ code1, payload1 ], 
     [ code2, payload2 ], 
     ... 
    ] 
} 

例如原始數據將是：

var streamSnapshot = []byte(

`{ 
    "ts": 1496244373.04, 
    "data":[ 
     ["xrate", {"rate":1.2916,"ccy":"USD"}], 
     ["balance", 
     { 
      "open_stake":["GBP", 0.0], 
      "balance":["GBP", 0.0] 
     } 
     ], 
     ["event", 
     { 
      "competition_id":"545", 
      "ir_status":"pre_event", 
      "start_time":"2017-09-10T17:00:00+00:00", 
      "competition_name":"USA NFL", 
      "event_id":"2017-09-10,21617,21635", 
      "home":"Buffalo Bills", 
      "away":"New York Jets", 
      "sport":"af", 
      "competition_country":"US" 
     } 
     ], 
     ["sync", {"Token":"eb1c57132d004f8d8fb967c076921fac"}] 
    ] 
}`) 

考慮到我們要避免解組一個struct像這樣：

type StreamMessage struct { 
    Data [][]interface{} `json:"data"` 
    Ts float64   `json:"ts"` 
} 

在那裏我們將不得不將數據施放回來：

m := raw.(map[string]interface{}) 

    switch messageType { 
    case XRATE: 
     xrate := XRate{ 
      Message: Message{ 
       Type:  XRATE, 
       TimeStamp: msg.Ts, 
      }, 
      rate: m["rate"].(float64), 
      ccy: m["ccy"].(string), 
     } 
    ... 

解組這個更好的方法是什麼？

Answer 1

package main 

import (
    "bytes" 
    "encoding/json" 
    "errors" 
    "fmt" 
) 

type StreamMessage struct { 
    Data []*Data `json:"data"` 
    Ts float64 `json:"ts"` 
} 

type Data struct { 
    Type string 
    XRate *XRateData 
    Balance *BalanceData 
    Event *EventData 
    Sync *SyncData 
} 

func (d *Data) UnmarshalJSON(b []byte) error { 
    dec := json.NewDecoder(bytes.NewReader(b)) 
    t, _ := dec.Token() 
    if delim, ok := t.(json.Delim); !ok || delim != '[' { 
     return errors.New("expecting data to be an array") 
    } 

    if err := dec.Decode(&d.Type); err != nil { 
     return err 
    } 

    var err error 
    switch d.Type { 
    case "xrate": 
     err = dec.Decode(&d.XRate) 
    case "sync": 
     err = dec.Decode(&d.Sync) 
    case "balance": 
     err = dec.Decode(&d.Balance) 
    case "event": 
     err = dec.Decode(&d.Event) 
    default: 
     return errors.New("unknown data type " + d.Type) 
    } 

    if err != nil { 
     return err 
    } 

    t, _ = dec.Token() 
    if delim, ok := t.(json.Delim); !ok || delim != ']' { 
     return errors.New("expecting array to be two elements") 
    } 

    return nil 
} 

type XRateData struct { 
    Rate json.Number `json:"rate"` 
    CCY string  `json:"ccy"` 
} 

type BalanceData struct { 
    // TODO 
} 

type EventData struct { 
    // TODO 
} 

type SyncData struct { 
    Token string `json:"Token"` 
} 

var streamSnapshot = []byte(

    `{ 
    "ts": 1496244373.04, 
    "data":[ 
     ["xrate", {"rate":1.2916,"ccy":"USD"}], 
     ["balance", 
     { 
      "open_stake":["GBP", 0.0], 
      "balance":["GBP", 0.0] 
     } 
     ], 
     ["event", 
     { 
      "competition_id":"545", 
      "ir_status":"pre_event", 
      "start_time":"2017-09-10T17:00:00+00:00", 
      "competition_name":"USA NFL", 
      "event_id":"2017-09-10,21617,21635", 
      "home":"Buffalo Bills", 
      "away":"New York Jets", 
      "sport":"af", 
      "competition_country":"US" 
     } 
     ], 
     ["sync", {"Token":"eb1c57132d004f8d8fb967c076921fac"}] 
    ] 
}`) 

func main() { 
    var sm StreamMessage 
    if err := json.Unmarshal(streamSnapshot, &sm); err != nil { 
     panic(err) 
    } 
    fmt.Println(sm) 
} 

https://play.golang.org/p/ktABS6z40m