[笔记]Go语言实现同一结构体适配多种消息源

问题：

提供天气信息的网站有很多，每家的数据及格式都不同，为了适配各种不同的天气接口，写了如下程序。

代码如下：

package main

import (
  "encoding/json"
  "errors"
  "fmt"
  "regexp"
  "strconv"
  "strings"
)

var s string = `
{
    "error": 0,
    "status": "success",
    "date": "2015-03-26",
    "results": [
        {
            "test": [
                [
                    "fuck",
                    "shit"
                ],
                {
                    "ao": "xxx"
                },
                "vfe"
            ],
            "currentCity": "郑州",
            "pm25": "95",
            "index": [
                {
                    "title": "穿衣",
                    "zs": "较冷",
                    "tipt": "穿衣指数",
                    "des": "建议着厚外套加毛衣等服装。年老体弱者宜着大衣、呢外套加羊毛衫。"
                },
                {
                    "title": "洗车",
                    "zs": "不宜",
                    "tipt": "洗车指数",
                    "des": "不宜洗车，未来24小时内有雨，如果在此期间洗车，雨水和路上的泥水可能会再次弄脏您的爱车。"
                },
                {
                    "title": "旅游",
                    "zs": "适宜",
                    "tipt": "旅游指数",
                    "des": "温度适宜，又有较弱降水和微风作伴，会给您的旅行带来意想不到的景象，适宜旅游，可不要错过机会呦！"
                },
                {
                    "title": "感冒",
                    "zs": "少发",
                    "tipt": "感冒指数",
                    "des": "各项气象条件适宜，无明显降温过程，发生感冒机率较低。"
                },
                {
                    "title": "运动",
                    "zs": "较不宜",
                    "tipt": "运动指数",
                    "des": "有降水，推荐您在室内进行健身休闲运动；若坚持户外运动，须注意保暖并携带雨具。"
                },
                {
                    "title": "紫外线强度",
                    "zs": "最弱",
                    "tipt": "紫外线强度指数",
                    "des": "属弱紫外线辐射天气，无需特别防护。若长期在户外，建议涂擦SPF在8-12之间的防晒护肤品。"
                }
            ],
            "weather_data": [
                {
                    "date": "周四 03月26日 (实时：12℃)",
                    "dayPictureUrl": "http://api.map.baidu.com/images/weather/day/zhenyu.png",
                    "nightPictureUrl": "http://api.map.baidu.com/images/weather/night/duoyun.png",
                    "weather": "阵雨转多云",
                    "wind": "微风",
                    "temperature": "12 ~ 4℃"
                },
                {
                    "date": "周五",
                    "dayPictureUrl": "http://api.map.baidu.com/images/weather/day/qing.png",
                    "nightPictureUrl": "http://api.map.baidu.com/images/weather/night/qing.png",
                    "weather": "晴",
                    "wind": "微风",
                    "temperature": "16 ~ 8℃"
                },
                {
                    "date": "周六",
                    "dayPictureUrl": "http://api.map.baidu.com/images/weather/day/qing.png",
                    "nightPictureUrl": "http://api.map.baidu.com/images/weather/night/duoyun.png",
                    "weather": "晴转多云",
                    "wind": "微风",
                    "temperature": "22 ~ 9℃"
                },
                {
                    "date": "周日",
                    "dayPictureUrl": "http://api.map.baidu.com/images/weather/day/qing.png",
                    "nightPictureUrl": "http://api.map.baidu.com/images/weather/night/qing.png",
                    "weather": "晴",
                    "wind": "微风",
                    "temperature": "25 ~ 11℃"
                }
            ]
        }
    ]
}
`

// 天气
type Weather struct {
  Error_Code string `json:"error_code"` //错误码  0没有错误
  Status     string `json:"status"`     // 状态描述, success 成功
  Result     Result `json:"result"`     // 天气状况
}

// 天气结果
type Result struct {
  Now         Real
  LivingIndex []Indicate `json:"living_index"` //生活指数
  Future      []ForeCast `json:"future"`       //未来几天的预报，包括当天
}

// 实时报告
type Real struct {
  City          string `json:"city"`           // 城市
  Temperature   string `json:"temperature"`    // 当前温度
  WindDirection string `json:"wind_direction"` // 风向
  WindStrength  string `json:"wind_strength"`  // 风强度
  Humidity      string `json:"humidity"`       // 湿度
  PM25          string `json:"pm25"`           // PM2.5
}

// 预报
type ForeCast struct {
  Temperature string `json:"temperature"` // 温度范围
  Weather     string `json:"weather"`     // 天气  （晴，多云，阴转多云）
  Wind        string `json:"wind"`        // 风向和强度
  Week        string `json:"week"`        // 星期几
  Date        string `json:"date"`        // 日期
}

type Indicate struct {
  Title       string `json:"titile"` // 指数标题
  Status      string `json:"status"` //指数状态 (适宜，不宜)
  Description string `json:"desc"`   //描述信息
}

func NewWeather() *Weather {
  return NewWeatherWithNum(6, 4)
}

func NewWeatherWithNum(livingIndexNum, forecastNum int) *Weather {
  w := &Weather{}
  w.Result.LivingIndex = make([]Indicate, livingIndexNum)
  w.Result.Future = make([]ForeCast, forecastNum)
  return w
}

type ElementExtractor struct {
  Err error
  m   map[string]interface{}
  r   *regexp.Regexp
}

func NewElementExtractor(jsonString string) *ElementExtractor {
  ee := &ElementExtractor{r: regexp.MustCompile(`(.*)\[(\d+)\]+`)}
  ee.Err = json.Unmarshal([]byte(jsonString), &ee.m)
  return ee
}

func (ee *ElementExtractor) ExtractElementByPattern(patten string) (string, error) {
  if ee.Err != nil {
    return "", ee.Err
  }

  var mm map[string]interface{} = ee.m
  var sa []interface{}

  patten = strings.Replace(patten, "][", "].[", -1)

  for _, k := range strings.Split(patten, ".") {
    ki := ee.r.FindStringSubmatch(k)
    if len(ki) == 3 {
      j, _ := strconv.Atoi(ki[2])
      if ki[1] != "" {
        sa = mm[ki[1]].([]interface{})
      }

      switch s := sa[j].(type) {
      case string:
        return s, nil
      case map[string]interface{}:
        mm = s
      case []interface{}:
        sa = sa[j].([]interface{})
      default:
        return fmt.Sprintf("%v", s), nil
      }
    } else {
      switch s := mm[k].(type) {
      case string:
        return s, nil
      case map[string]interface{}:
        mm = s
      default:
        return fmt.Sprintf("%v", s), nil
      }
    }
  }

  ee.Err = errors.New("Pattern Error: " + patten)
  return "", ee.Err
}

func main() {
  ee := NewElementExtractor(s)
  w := NewWeather()

  w.Status, _ = ee.ExtractElementByPattern("status")
  w.Error_Code, _ = ee.ExtractElementByPattern("error")
  w.Result.Now.City, _ = ee.ExtractElementByPattern("results[0].currentCity")
  w.Result.Now.PM25, _ = ee.ExtractElementByPattern("results[0].pm25")
  w.Result.Future[2].Date, _ = ee.ExtractElementByPattern("results[0].weather_data[2].date")
  w.Result.LivingIndex[0].Title, _ = ee.ExtractElementByPattern("results[0].index[0].title")
  w.Result.Future[2].Temperature, _ = ee.ExtractElementByPattern("results[0].weather_data[2].temperature")
  w.Result.Now.PM25, _ = ee.ExtractElementByPattern("results[0].test[0][1]")
  w.Result.Now.WindDirection, _ = ee.ExtractElementByPattern("results[0].test[1].ao")
  w.Result.Now.WindStrength, _ = ee.ExtractElementByPattern("results[0].test[2]")

  if ee.Err != nil {
    fmt.Println(ee.Err)
  } else {
    fmt.Println(w)
  }
}

运行结果：

&{0 success {{郑州  xxx vfe  shit} [{穿衣  } {  } {  } {  } {  } {  }] [{    } {    } {22 ~ 9℃    周六} {    }]}}