handling int64 numbers

[Jim Robinson]

Hi folks,

The documentation I've read so far appears slightly vague

about how to properly handle reading int64 values out of

mongo when using mgo.

Is the proper technique something along the lines of the following,

for the example of a incrementing a sequence counter?

...

collection := session.DB(db).C(collection)

locate := bson.M{"_id": id}

change := mgo.Change{

Update:    bson.M{"$inc": bson.M{"n": 1}},

Upsert:    true,

ReturnNew: true}

result := bson.M{}

info, err := collection.Find(locate).Apply(change, &result)

...

var n int64

switch t := result["n"].(type) {

case int:

  n = int64(t)

case int32:

  n = int64(t)

case int64:

  n = t

default:

  ... error case ...

}

[Jim Robinson]

Ah, it appears that an alternative is to provide my own struct with bson: labels.

type Sequence struct {

Id string `bson:"_id"`

N  int64  `bson:"n"`

}

...

collection := session.DB(db).C(collection)

locate := bson.M{"_id": id}

change := mgo.Change{

Update:    bson.M{"$inc": bson.M{"n": 1}},

Upsert:    true,

ReturnNew: true}

result := &Sequence{}

info, err := collection.Find(locate).Apply(change, result)

...

return result.N, err