Primitive.ObjectID to string in Golang

Question

I am trying to convert type primitive.ObjectID to string type in Go. I am using mongo-driver from go.mongodb.org/mongo-driver.

I tried using type assertion like-

mongoId := mongoDoc["_id"];
stringObjectID := mongoId.(string)

Which VSCode accepts. Code gets compiled and when it reaches this specific line of code, it throws this error

panic: interface conversion: interface {} is primitive.ObjectID, not string

It's impossible to tell you how to convert `primitive.ObjectID` to a string if you don't tell us how `primitive.ObjectID` is defined. — Jonathan Hall, Mar 26 '20 at 10:21
hi Flimzy, It was defined like this var parentOrder bson.M; and appened into slice array, and the slice array was defined like this var mapArray []bson.M Function loops through this slice array to scan _id like I explained above. mongoDoc is one single mongo document of type bson.M — Rabi, Mar 26 '20 at 10:31

score 36 · Accepted Answer · answered Mar 26 '20 at 10:26

36

The error message tells mongoDoc["_id"] is of type interface{} which holds a value of type primitive.ObjectID. This is not a string, it's a distinct type. You can only type assert primitive.ObjectID from the interface value.

If you want a string representation of this MongoDB ObjectId, you may use its ObjectID.Hex() method to get the hex representation of the ObjectId's bytes:

mongoId := mongoDoc["_id"]
stringObjectID := mongoId.(primitive.ObjectID).Hex()

answered Mar 26 '20 at 10:26

icza

389,944
63
907
827

2

Thanks a lot. You saved my life. It worked like magic. Thanks again – Rabi Mar 26 '20 at 16:49
how to convert a string to object ID? – Rohan Devaki Oct 09 '21 at 08:54
nowadays you can just do mongoId.Hex() – bashizip Nov 27 '21 at 14:32
1

@bashizip Yes, that's what the answer says. If you have an `ObjectID`, you may call its `Hex()` method. The type assertion is needed if you have the document in a map with `interface{}` value type. – icza Nov 27 '21 at 16:17
@icza thank you for the precision, I'm still new to golang and I just learn something from you – bashizip Nov 27 '21 at 20:30

Bitfinicon · Answer 2 · 2021-09-22T18:21:24.290

Things have changed in 2021. Here is a more easy way. It takes the user from models asking what kind of type it is from interface then all good

var user models.User

query := bson.M{"$or": []bson.M{{"username": data["username"]}, {"email": data["username"]}}}

todoCollection := config.MI.DB.Collection(os.Getenv("DATABASE_COLLECTION_USER"))
todoCollection.FindOne(c.Context(), query).Decode(&user)

stringObjectID := user.ObjectID.Hex()

Above code works with this interface:

type User struct {
    ObjectID primitive.ObjectID `bson:"_id" json:"_id"`

    // Id        string    `json:"id" bson:"id"`
    Username      string    `json:"username" gorm:"unique" bson:"username,omitempty"`
    Email         string    `json:"email" gorm:"unique" bson:"email,omitempty"`
    Password      []byte    `json:"password" bson:"password"`
    CreatedAt     time.Time `json:"createdat" bson:"createat"`
    DeactivatedAt time.Time `json:"updatedat" bson:"updatedat"`
}

So consequently: this 3 line codes would do it nicely:

objectidhere := primitive.NewObjectID()
stringObjectID := objectidhere.Hex()

filename_last := filename_rep + "_" + stringObjectID + "." + fileExt

for bongo package in go use code userModel.DocumentBase.GetId().Hex() — Manish Sharma, Jan 08 '22 at 15:24

score 4 · Answer 3 · answered Nov 27 '21 at 14:33

4

nowadays you can just do mongoId.Hex()

answered Nov 27 '21 at 14:33

bashizip

562
5
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score 1 · Answer 4 · answered Mar 26 '21 at 05:00

1

var stringObjectId string = mongoId.(primitive.ObjectID).String()

answered Mar 26 '21 at 05:00

patrik kings

442
6
15

Primitive.ObjectID to string in Golang

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