Thanks. after reading your reply I was able to reduce the example to just a few lines, the key was to know that maps in Go are pointers, like slices are pointers too.
https://play.golang.org/p/-x1R2P5IrF package main import ( "fmt" ) func main() { var docs []interface{} doc1 := map[string]int{ "uno": 1, } docs = append(docs, doc1) fmt.Println("doc1 appended is: ", docs) //doc1 = nil //this would reset the doc1 variable so it is not "poining" to the map stored in the docs slice //doc1 = make(map[string]int) // if we make doc1 nil, then we need to initialize it again doc1["uno"] = 2 fmt.Println("Updated the doc1 map value and now docs is: ", docs) } prints: ======================== doc1 appended is: [map[uno:1]] Updated the doc1 map value and now docs is: [map[uno:2]] ======================== Thanks Diego On Monday, October 24, 2016 at 7:10:25 PM UTC-4, kortschak wrote: > > I would guess this is because when iter.Next is given a nil bson.M is > needs to make a new value to fill (which from your output is a map). > When it is handed a bson.M that already has a map in it, it can use > that. Remember that bson.M is just interface{} and maps are pointer- > like. > > On Mon, 2016-10-24 at 11:56 -0700, Diego Medina wrote: > > Hi (sorry for the cryptic subject, I'm just not sure what to even > > call > > this): > > > > > > I think this is not strictly a mgo question, I have this simplified > > function that gets documents from a mongo instance using Iter(), I > > then > > loop through the results, append them to a slice []interface{} but > > the > > resulting new slice has the last element repeated N times, where N is > > the > > number of item I got from the call to Iter(). > > > > In code on gist: > > > > https://gist.github.com/fmpwizard/a1b4cc246b5875ff6bd1fbcd71940703 > > > > pasted here: > > > > > > func TestBatchInsert1(t *testing.T) { > > c := session.DB("testing").C("delete") > > c.DropCollection() > > > > c.Insert(bson.M{ > > "name": "AAAAAAA", > > "num": 1, > > }) > > > > c.Insert(bson.M{ > > "name": "BBBBBBBB", > > "num": 2, > > }) > > > > iter := c.Find(nil).Iter() > > //var doc interface{} //if I use this line instead of a bson.M, the > > "issue" > > doesn't happen > > var doc bson.M > > var docs []interface{} > > > > for iter.Next(&doc) { > > fmt.Printf("Pre append\n\n %+v\n\n", docs) > > docs = append(docs, doc) > > fmt.Printf("Post append\n\n %+v\n\n", docs) > > //doc = nil //This **fixes** it but why? > > } > > fmt.Printf("Final\n\n %+v\n\n", docs) > > > > err := iter.Close() > > if err != nil { > > fmt.Printf("Failed to close iter during copy: %s", err) > > } > > } > > > > > > the output of all that is: > > > > Pre append > > > > [] > > > > Post append > > > > [map[_id:ObjectIdHex("580e5758ad817545b924a2c1") name:AAAAAAA > > num:1]] > > > > Pre append > > > > [map[_id:ObjectIdHex("580e5758ad817545b924a2c2") name:BBBBBBBB > > num:2]] > > > > Post append > > > > [map[_id:ObjectIdHex("580e5758ad817545b924a2c2") name:BBBBBBBB > > num:2] > > map[_id:ObjectIdHex("580e5758ad817545b924a2c2") name:BBBBBBBB num:2]] > > > > Final > > > > [map[_id:ObjectIdHex("580e5758ad817545b924a2c2") name:BBBBBBBB > > num:2] > > map[_id:ObjectIdHex("580e5758ad817545b924a2c2") name:BBBBBBBB num:2]] > > > > > > =========================== > > > > note how the second time we print "Pre append" the docs slice has is > > the > > second item in it, instead of the first one: > > > > [map[_id:ObjectIdHex("580e5758ad817545b924a2c2") name:BBBBBBBB > > num:2]] > > > > as if I appended a pointer to the docs instead the actual value of > > doc. > > > > I found two ways to avoid this issue, one is to uncomment > > > > //doc = nil // > > > > after calling append, I just don't understand why I need to reset it. > > > > The other is, instead of working with > > > > var doc bson.M > > var docs []interface{} > > > > I can use > > > > var doc interface{} > > var docs []interface{} > > > > but using > > > > var doc bson.M > > var docs []bson.M > > > > also shows the **issue** > > > > Thanks. > > > > Diego > > > -- 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. For more options, visit https://groups.google.com/d/optout.
