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gobson

How to convert bson.Binary to []byte in Go

I'm writing a small application that receives message in BSON format from network(its not MongoDB) and have to save fields in files on local machine. I'm using gopkg.in/mgo.v2/bson for message unmarshaling and it works fine.

Almost everything works except one. There "userdefined" binary field in message and I have to save it to separate file. I tried to use:

var pwr = msg["pwr"].([]byte)

but got an "error panic: interface conversion: interface is bson.Binary, not []uint8".

Can some one point me an example how to convert bson.Binary to []byte, so I can save it to file.

Solution

  • This does what you want:

    pwr := bson.Binary(msg["pwr"].(bson.Binary)).Data

    But assumes msg["pwr"] can't be anything other than a bson.Binary... if that's not an invariant you should do the type assertion first (handle the possible type mismatch case when it happens) and then cast to get the Data field.