问题
I have a mongo document which contains a date field which can also be false (or not defined), and I can't seem to find how to check if the field is available OR is false OR is a date (time.Time) in golang/mgo :S
回答1:
If you have a time.Time field, and want to know whether it was properly set with a valid date, you can query its IsZero() method. Otherwise, if you're trying to query the database for such a document, you can do one of the following.
Query if the field is false:
iter := collection.Find(bson.M{"field": false}).Iter()
Query if the field is available, with the $exists operator:
iter := collection.Find(bson.M{"field": bson.M{"$exists": true}}).Iter()
Query if the field is a date, using the $type operator:
iter := collection.Find(bson.M{"field": bson.M{"$type": 9}}).Iter()
来源：https://stackoverflow.com/questions/18721801/mgo-time-time-or-boolean-check