src/github.com/mongodb/mongo-go-driver/mongo/cursor.go 游标的简洁实用

src/github.com/mongodb/mongo-go-driver/mongo/cursor.go

// Copyright (C) MongoDB, Inc. 2017-present.
//
// Licensed under the Apache License, Version 2.0 (the "License"); you may
// not use this file except in compliance with the License. You may obtain
// a copy of the License at http://www.apache.org/licenses/LICENSE-2.0

package mongo

import (
   "context"

   "github.com/mongodb/mongo-go-driver/bson"
)

// Cursor instances iterate a stream of documents. Each document is
// decoded into the result according to the rules of the bson package.
//
// A typical usage of the Cursor interface would be:
//
//    var cur Cursor
//    ctx := context.Background()
//    defer cur.Close(ctx)
//
//        for cur.Next(ctx) {
//       elem := bson.NewDocument()
//       if err := cur.Decode(elem); err != nil {
//              log.Fatal(err)
//           }
//
//           // do something with elem....
//    }
//
//        if err := cur.Err(); err != nil {
//       log.Fatal(err)
//    }
//
type Cursor interface {
   // NOTE: Whenever ops.Cursor changes, this must be changed to match it.

   // Get the ID of the cursor.
   ID() int64

   // Get the next result from the cursor.
   // Returns true if there were no errors and there is a next result.
   Next(context.Context) bool

   Decode(interface{}) error

   DecodeBytes() (bson.Reader, error)

   // Returns the error status of the cursor
   Err() error

   // Close the cursor.
   Close(context.Context) error
}