val["author"].(primitive.A)[0] is correct, but the type of that expression is not author, it is bson.M. You might consider using a tagged struct to unmarshal this.
On Thu, Nov 16, 2023 at 10:11 AM Tong Sun <suntong...@gmail.com> wrote: > > Further on with the question > https://stackoverflow.com/questions/60072372/filtering-values-out-of-a-bson-m-in-golang/ > where the answer says to use `range server.installed` while the comment says > > server.host undefined (type string has no field or method subject) > > This is what I've tried with the MongoDB `[]bson.M{}` type results (obtained > from like `$lookup`): > > The []bson.M{} type of result I'm getting is: > > [map[_id:ObjectID("65529d178688bac31b739f82") > author:[map[_id:ObjectID("65529d168688bac31b739f81") created_at:1699912982379 > name:Mehran updated_at:1699912982379]] > author_id:ObjectID("65529d168688bac31b739f81") created_at:1699912983386 > name:Test pages:124 updated_at:1699912983386]] > > I've made several attempts but was unable to access the author field of the > lookup result in Go. > > a := []author{} > for _, val := range result { a = append(a, val["author"].(primitive.A)[0]) } > > If using val.author, I'm getting val.author undefined (type primitive.M has > no field or method author) > If using val["author"], I'm getting invalid operation: cannot index > val["author"] (map index expression of type interface{}) > If using val["author"].(primitive.A)[0], I'm getting cannot use > val["author"].(primitive.A)[0] (variable of type interface{}) as author value > in argument to append: need type assertion > > > And how to go about to fix this "need type assertion" just stumbled me, as > I've tried val["author"].(primitive.A).([]main.author)[0], or > []author(val["author"].(primitive.A))[0], but I'm getting invalid operation: > cannot call non-function val["author"].(primitive.A) (comma, ok expression of > type primitive.A) > > and I've now run out of ideas how to fix it. > Please help > > > -- > You received this message because you are subscribed to the Google Groups > "golang-nuts" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to golang-nuts+unsubscr...@googlegroups.com. > To view this discussion on the web visit > https://groups.google.com/d/msgid/golang-nuts/4c9bfd40-4de6-4423-9c0e-31b79b144bd5n%40googlegroups.com. -- You received this message because you are subscribed to the Google Groups "golang-nuts" group. To unsubscribe from this group and stop receiving emails from it, send an email to golang-nuts+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/golang-nuts/CAMV2Rqr55hWi0XwSunq%3D4eJ6OMG1bT45T0ac4p%3D1KneAC96rCQ%40mail.gmail.com.
