MongoDB中Golang中的聚合和过滤

Question

i use https://github.com/Kamva/mgm for my Golang project with MongoDB as database. I´ve been searching a way to aggregate and filter a collection.

Here my working Aggregation of the Author (a user) of a article:

authorCollName := mgm.Coll(&Models.User{}).Name()
articles := []Models.Article{}

err = mgm.Coll(&Models.Article{}).SimpleAggregate(&articles, builder.Lookup(authorCollName, "authorid", "_id", "author"))

But i want filter it on a specific category like here in this simple find:

err = collection.SimpleFind(&articles, bson.D{{"category", objID}})

The Models:

type Article struct {
    mgm.DefaultModel `bson:",inline"`
    Name             string             `json:"name" bson:"name"`
    AuthorId         primitive.ObjectID `json:"authorId" bson:"authorid"`
    Author           []User             `json:"author" form:"author"`
    Category         primitive.ObjectID `json:"category,omitempty"`
}

type User struct {
    mgm.DefaultModel  `bson:",inline"`
    Forename          string   `json:"forename"`
    Name              string   `json:"name"`
    Email             string   `json:"email"`
    Password          string   `json:"password"`
}

Can someone give me a hint, how i can solve it that i can use aggregation and a filter together?

Answer 1

Thank you prsad_! You save my day! The solution:

err = mgm.Coll(&Models.Article{}).SimpleAggregate(&articles, builder.Lookup(authorCollName, "authorid", "_id", "author"), M{operator.Match: M{"category": objID}})