drmcm84800
2017-09-06 18:20
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Golang在解组JSON时删除字符串前缀

In my json data structure I have a string that can have a prefix. When unmarshalling JSON, is it possible to have a function to remove that prefix? I am looking into custom JSON unmarshalling in golang and trying to leverage that.

For example. The payload can be either of the following

{
  "id": "urn:uuid:1234567890"
}

{
  "id": "1234567890"
}

When I do JSON.unmarshall(data, &struct) I'd like the unmarshall function to handle removing the urn:uuid prefix from the string if it is there so the struct will always have the value 1234567890 for id.

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1条回答 默认 最新

  • dongxun5349 2017-09-06 19:19
    已采纳

    You can provide a custom UnmarshalJSON method on the data you need to trim, here is an example implementation, you may need to extend if you have to regex match the start rather than match hard string (or byte array in this case):

    go playground

    package main
    
    import (
        "bytes"
        "encoding/json"
        "log"
    )
    
    var (
        sampleJSON   = []byte(`{"id": "urn:uuid:1234567890"}`)
        prefixToTrim = []byte(`urn:uuid:`)
    )
    
    type IDField string
    
    type Data struct {
        ID IDField `json:"id"`
    }
    
    func main() {
        d := &Data{}
        err := json.Unmarshal(sampleJSON, d)
        if err != nil {
            log.Fatal(err)
        }
    
        log.Println(d.ID)
    }
    
    // UnmarshalJSON provides custom unmarshalling to trim `urn:uuid:` prefix from IDField
    func (id *IDField) UnmarshalJSON(rawIDBytes []byte) error {
    
        // trim quotes and prefix
        trimmedID := bytes.TrimPrefix(bytes.Trim(rawIDBytes, `"`), prefixToTrim)
    
        // convert back to id field & assign
        *id = IDField(trimmedID)
        return nil
    }
    
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