英文:
Custom JSON Unmarshalling for string-encoded number
问题
我有一个包含各种货币值的struct
,以分为单位(1/100 美元):
type CurrencyValues struct {
v1 int `json:"v1,string"`
v2 int `json:"v2,string"`
}
我想为具有千位分隔符的货币值创建一个自定义的 JSON 反序列化器。这些值被编码为字符串,其中包含一个或多个千位分隔符(,
),可能还有一个小数点(.
)。
对于这个 JSON { "v1": "10", "v2": "1,503.21" }
,我想要 JSON 反序列化为 CurrencyValues{v1: 1000, v2: 150321}
。
根据这里的一个类似答案:https://stackoverflow.com/questions/30856454/golang-how-to-unmarshall-both-0-and-false-as-bool-from-json,我创建了一个自定义类型来表示我的货币字段,并包含一个自定义的反序列化函数:
type ConvertibleCentValue int
func (cents *ConvertibleCentValue) UnmarshalJSON(data []byte) error {
asString := string(data)
// 移除千位分隔符
asString = strings.Replace(asString, ",", "", -1)
// 解析为浮点数,然后将美元转换为分
if floatVal, err := strconv.ParseFloat(asString, 32); err == nil {
*cents = ConvertibleCentValue(int(floatVal * 100.0))
return nil
} else {
return err
}
}
然而,在编写单元测试时:
func Test_ConvertibleCentValue_Unmarshal(t *testing.T) {
var c ConvertibleCentValue
assert.Nil(t, json.Unmarshal([]byte("1,500"), &c))
assert.Equal(t, 150000, int(c))
}
我遇到了这个错误:
Error: Expected nil, but got: &json.SyntaxError{msg:"invalid character ',' after top-level value", Offset:2}
我在这里漏掉了什么?
英文:
I have a struct
which contains various currency values, in cents (1/100 USD):
type CurrencyValues struct {
v1 int `json:"v1,string"`
v2 int `json:"v2,string"`
}
I'd like to create a custom json Unmarshaller for currency values with thousand separators. These values are encoded as strings, with one or more thousand separators (,
), and possibly a decimal point (.
).
For this JSON {"v1": "10", "v2": "1,503.21"}
, I'd like to JSON Unmarshal a CurrencyValues{v1: 1000, v2: 150321}
.
Following a similar answer here: https://stackoverflow.com/questions/30856454/golang-how-to-unmarshall-both-0-and-false-as-bool-from-json, I went ahead and created a custom type for my currency fields, which include a custom Unmarshalling function:
type ConvertibleCentValue int
func (cents *ConvertibleCentValue) UnmarshalJSON(data []byte) error {
asString := string(data)
// Remove thousands separators
asString = strings.Replace(asString, ",", "", -1)
// Parse to float, then convert dollars to cents
if floatVal, err := strconv.ParseFloat(asString, 32); err == nil {
*cents = ConvertibleCentValue(int(floatVal * 100.0))
return nil
} else {
return err
}
}
However, when writing unit tests:
func Test_ConvertibleCentValue_Unmarshal(t *testing.T) {
var c ConvertibleCentValue
assert.Nil(t, json.Unmarshal([]byte("1,500"), &c))
assert.Equal(t, 150000, int(c))
}
I encounter this error:
Error: Expected nil, but got: &json.SyntaxError{msg:"invalid character ',' after top-level value", Offset:2}
What am I missing here?
答案1
得分: 4
你正在尝试解析无效的JSON字符串1,500
。我认为你的意思是解析JSON字符串"1,500"
:
assert.Nil(t, json.Unmarshal([]byte(`"1,500"`), &c))
请注意反引号。这里是一个简化的示例:
b := []byte(`1,500`)
var s string
err := json.Unmarshal(b, &s)
fmt.Println(s, err) // 打印错误。
b = []byte(`"1,500"`)
err = json.Unmarshal(b, &s)
fmt.Println(s, err) // 正常工作。
Playground: http://play.golang.org/p/uwayOSgmTv.
英文:
You're trying to unmarshal the string 1,500
which is invalid in JSON. I think what you means is to unmarshal the JSON string "1,500"
:
assert.Nil(t, json.Unmarshal([]byte(`"1,500"`), &c))
Note the backticks. Here is a simplified example:
b := []byte(`1,500`)
var s string
err := json.Unmarshal(b, &s)
fmt.Println(s, err) // Prints error.
b = []byte(`"1,500"`)
err = json.Unmarshal(b, &s)
fmt.Println(s, err) // Works fine.
Playground: http://play.golang.org/p/uwayOSgmTv.
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