Golang,MongoDB, Having issues using $in to find all elements with one string in there array property

Question

I am trying to find all users in a MongoDB collection that contains a username string in the friends array. I am using Golang with the mgo driver.

   type User struct {
    ...
        Friends        []string    `json: friends bson:"friends,omitempty"` 
    ...
    }

    ...
    // username is a string
    arr := []string{username}

    err := c.Find(bson.M{"friends": {"$in": arr}}).All(&users)
    ...

I get this error: http: panic serving [::1]:56358: assignment to entry in nil map

Any help would be greatly appreciated.

khrm · Accepted Answer · 2016-05-15 00:55:36Z

23

You are using "$in" wrong. You aren't initialising inner map. You are supposed to use it like this:

err := c.Find(bson.M{"friends": bson.M{"$in": arr}}).All(&users)

answered May 15, 2016 at 0:55

khrm

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3 Comments

Kody Doherty Over a year ago

I tried that and now I get. http: panic serving [::1]:59541: assignment to entry in nil map

Kody Doherty Over a year ago

Never mind the issue was down the line in the HTTP response. You are correct that resolved the issue. Thank you for the help!

Kira Over a year ago

thanks, bson.M is much simpler to work than bson.D and bson.E

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