英文:
Why won't mgo unmarshall my struct properly?
问题
之前我发布了这个问题，询问如何在Go中使用mgo编写自定义的BSON编组/解组。现在我来测试它，我觉得我遇到了一个更大的问题。我的所有结构体都解组为nil值。
这是我的货币结构体，其中包含了bson.Getter和bson.Setter的实现：
type Currency struct {
value decimal.Decimal // 货币的实际值。
currencyCode string // ISO货币代码。
}
/*
GetBSON实现了bson.Getter接口。
*/
func (c Currency) GetBSON() (interface{}, error) {
f, _ := c.Value().Float64()
return bson.Marshal(struct {
Value float64 `json:"value" bson:"value"`
CurrencyCode string `json:"currencyCode" bson:"currencyCode"`
}{
Value: f,
CurrencyCode: c.currencyCode,
})
}
/*
SetBSON实现了bson.Setter接口。
*/
func (c *Currency) SetBSON(raw bson.Raw) error {
decoded := new(struct {
Value float64 `json:"value" bson:"value"`
CurrencyCode string `json:"currencyCode" bson:"currencyCode"`
})
fmt.Println(string(raw.Data))
bsonErr := raw.Unmarshal(decoded)
if bsonErr == nil {
fmt.Println("Debug: no error returned.")
fmt.Println(decoded)
c.value = decimal.NewFromFloat(decoded.Value)
c.currencyCode = decoded.CurrencyCode
return nil
} else {
return bsonErr
}
}
通过查看原始数据，它正确地进行了编组，但是在解组时，得到的结构体为空。你有什么想法，我在哪里出错了？我昨天刚刚使用go get gopkg.in/mgo.v2命令，所以我希望它是最新的，而且不会出现这样的错误，因为它是“最热门的MongoDB驱动程序”。
英文:
Earlier I posted this question asking about writing custom BSON marshalling/unmarshalling in Go using mgo. Now I've come to test it I think I've hit on a bigger problem. All my structs unmarshal to nil values.
This is my currency struct with the implementations of bson.Getter and bson.Setter:
type Currency struct {
value decimal.Decimal //The actual value of the currency.
currencyCode string //The ISO currency code.
}
/*
GetBSON implements bson.Getter.
*/
func (c Currency) GetBSON() (interface{}, error) {
f, _ := c.Value().Float64()
return bson.Marshal(struct {
Value float64 `json:"value" bson:"value"`
CurrencyCode string `json:"currencyCode" bson:"currencyCode"`
}{
Value: f,
CurrencyCode: c.currencyCode,
})
}
/*
SetBSON implements bson.Setter.
*/
func (c *Currency) SetBSON(raw bson.Raw) error {
decoded := new(struct {
Value float64 `json:"value" bson:"value"`
CurrencyCode string `json:"currencyCode" bson:"currencyCode"`
})
fmt.Println(string(raw.Data))
bsonErr := raw.Unmarshal(decoded)
if bsonErr == nil {
fmt.Println("Debug: no error returned.")
fmt.Println(decoded)
c.value = decimal.NewFromFloat(decoded.Value)
c.currencyCode = decoded.CurrencyCode
return nil
} else {
return bsonErr
}
}
By looking at the raw data, it marshals correctly, but when unmarshaling the resulting struct is just empty. Any ideas where I'm going wrong here? I used the go get gopkg.in/mgo.v2command literally yesterday so I would hope it was up to date and a bug like this wouldn't be present in "the hottest MongoDB driver around".
答案1
得分: 4
GetBSON 方法应该返回要进行编组的值，而不是编组后生成的二进制数据。这就是为什么它的第一个结果类型是 interface{} 而不是 []byte。
英文:
The GetBSON method should return the value to be marshaled, not the binary data resulting from marshaling it. That's why its first result type is interface{} and not []byte.
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