如何使用go-mongo-driver将BSON字符串值解组为自定义类型?

huangapple go评论75阅读模式
英文:

How to unmarshal a BSON string value into a custom type using go-mongo-driver?

问题

我正在使用MarshalBSONValue将内部结构字段编组为自定义字符串表示形式。

我无法弄清楚如何实现逆操作UnmarshalBSONValue,以便将自定义字符串表示形式解析为内部结构。

import (
	"fmt"
	"testing"

	"github.com/stretchr/testify/assert"
	"go.mongodb.org/mongo-driver/bson"
	"go.mongodb.org/mongo-driver/bson/bsontype"
)

type inner struct {
    value string
}

func (i inner) MarshalBSONValue() (bsontype.Type, []byte, error) {
	return bsontype.String, []byte(i.value), nil
}

// How to implement this?
//
// func (i *inner) UnmarshalBSONValue(t bsontype.Type, data []byte) error {
//     ...
// }

type Outer struct {
	Inner inner `bson:"inner"`
}

func TestMarshalBSON(t *testing.T) {
	var outer1 = Outer{Inner: inner{value: "value"}}
	doc, err := bson.Marshal(outer1)
	assert.NoError(t, err)
	fmt.Printf("%#v\n", string(doc)) // "\x11\x00\x00\x00\x02inner\x00value\x00"

	var outer2 Outer
	err = bson.Unmarshal(doc, &outer2) // error
	assert.NoError(t, err)

    assert.Equal(t, outer1, outer2)
}

如果有人能够为上述示例测试提供一个可行的UnmarshalBSONValue实现,我将非常感激。

英文:

I'm using MarshalBSONValue to marshal an inner struct field to a custom string representation.

I can't figure out how to implement the inverse operation, UnmarshalBSONValue, in order to parse the custom string representation into an inner struct.

import (
	"fmt"
	"testing"

	"github.com/stretchr/testify/assert"
	"go.mongodb.org/mongo-driver/bson"
	"go.mongodb.org/mongo-driver/bson/bsontype"
)

type inner struct {
    value string
}

func (i inner) MarshalBSONValue() (bsontype.Type, []byte, error) {
	return bsontype.String, []byte(i.value), nil
}

// How to implement this?
//
// func (i *inner) UnmarshalBSONValue(t bsontype.Type, data []byte) error {
//     ...
// }

type Outer struct {
	Inner inner `bson:"inner"`
}

func TestMarshalBSON(t *testing.T) {
	var outer1 = Outer{Inner: inner{value: "value"}}
	doc, err := bson.Marshal(outer1)
	assert.NoError(t, err)
	fmt.Printf("%#v\n", string(doc)) // "\x11\x00\x00\x00\x02inner\x00value\x00"

	var outer2 Outer
	err = bson.Unmarshal(doc, &outer2) // error
	assert.NoError(t, err)

    assert.Equal(t, outer1, outer2)
}

I would greatly appreciate it if anyone could provide a working implementation of UnmarshalBSONValue for the example test above.

答案1

得分: 4

你可以使用bsoncore.ReadString来解析给定的值。

func (i inner) MarshalBSONValue() (bsontype.Type, []byte, error) {
	return bson.MarshalValue(i.value)
}

func (i *inner) UnmarshalBSONValue(t bsontype.Type, value []byte) error {
	if t != bsontype.String {
		return fmt.Errorf("无效的 bson 值类型 '%s'", t.String())
	}
	s, _, ok := bsoncore.ReadString(value)
	if !ok {
		return fmt.Errorf("无效的 bson 字符串值")
	}

	i.value = s
	return nil
}
英文:

You can use bsoncore.ReadString to parse the given value.

func (i inner) MarshalBSONValue() (bsontype.Type, []byte, error) {
	return bson.MarshalValue(i.value)
}

func (i *inner) UnmarshalBSONValue(t bsontype.Type, value []byte) error {
	if t != bsontype.String {
		return fmt.Errorf("invalid bson value type '%s'", t.String())
	}
	s, _, ok := bsoncore.ReadString(value)
	if !ok {
		return fmt.Errorf("invalid bson string value")
	}

	i.value = s
	return nil
}

huangapple
  • 本文由 发表于 2021年7月18日 12:29:56
  • 转载请务必保留本文链接:https://go.coder-hub.com/68426012.html
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