如何使用go从mongoDB数组中获取所有元素？

Question

I am very new to mongodb and golang. I have a collection named "myplace" inside that, one field named region which is an array of values how we can retrieve the whole array.

my collection look likes

{
"_id" : ObjectId("5474227309d76eb732acd134"),
"City" : "some city",
"region" : [ 
    {
        "regionid" : "31",
        "historical_place" : "temple"

    }, 
    {
        "regionid" : "32",
        "historical_place" : "temple"
    }, 
    {
         "regionid" : "33",
        "historical_place" : "temple"

    }
]
}

Expecting output

 [
  {
    "City": "Some CIty",
    "region":[ 
     {
        "regionid" : "31",
        "historical_place" : "temple"

     }, 
    {
        "regionid" : "32",
        "historical_place" : "temple"
    }, 
    {
         "regionid" : "33",
        "historical_place" : "temple"

    }
   ]
  }
]

Any solution?

Answer 1

Create structs with bson tags and use mgo's Find().All(). And if you need an JSON output, use encoding/json package and MarshalIndent() function:

package main

import (
    "encoding/json"
    "fmt"
    "gopkg.in/mgo.v2"
    "gopkg.in/mgo.v2/bson"
    "log"
)

type City struct {
    ID     bson.ObjectId `bson:"_id,omitempty" json:"-"`
    Name   string        `bson:"City"`
    Region []Place       `bson:"region"`
}

type Place struct {
    RegionID  string `bson:"regionid"`
    HistPlace string `bson:"historical_place"`
}

func main() {
    session, err := mgo.Dial("127.0.0.1")
    if err != nil {
        panic(err)
    }
    defer session.Close()

    c := session.DB("db").C("myplaces")

    var cities []City
    err = c.Find(nil).All(&cities)
    if err != nil {
        log.Fatal(err)
    }

    out, err := json.MarshalIndent(cities, " ", " ")
    if err != nil {
        log.Fatal(err)
    }
    fmt.Println("Result:", string(out))
}