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 intfunc (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 ConvertibleCentValueassert.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 intfunc (cents *ConvertibleCentValue) UnmarshalJSON(data []byte) error {asString := string(data)// Remove thousands separatorsasString = strings.Replace(asString, ",", "", -1)// Parse to float, then convert dollars to centsif 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 ConvertibleCentValueassert.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 stringerr := 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 stringerr := 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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