将influxdb结果读入字符串会导致错误：interface {}是json.Number，而不是字符串

Question

I'm trying to convert an influxdb record (type: []interface{}) to []string so I can write it to csv.

Record

[2018-12-20T07:26:23Z 90 123.2132 12.3232 30 1 user]

Code

s := make([]string, len(record))
for i, v := range record {
    s[i] = v.(string)
}

But I got this error

interface {} is json.Number, not string

I'm new to golang and not too familiar with interface and json

Answer 1

I believe your record array is generated somewhat like this by your database driver:

record := make([]interface{}, 0, 10)
dec := json.NewDecoder(strings.NewReader(`["2018-12-20T07:26:23Z", 90, 123.2132, 12.3232, 30, 1, "user"]`))
dec.UseNumber()
dec.Decode(&record)

All numbers are generated as json.Number instead float64. Since json.Number support a simple conversion to string, you may use that interface along with a simple type switch to do this:

s := make([]string, len(record))
for i, v := range record {
    switch val := v.(type) {
    case string:
        s[i] = val
    case json.Number:
        s[i] = val.String()
    default:
        panic(fmt.Sprintf("unhandled type: %T", v))
    }
}

See this in action: https://play.golang.org/p/jD_z94vQ7Wt