使用Golang将响应映射到结构

Question

I am attempting to map a response from an API to a struct using Golang.

The JSON that comes back when I view the link in the browser is below:

{
"GBP": 657.54
}

And I just want to map it to a simple struct like so:

type Price struct {
    Name  string
    Value float64
}

Here is my current code.

func FetchCoinPrice(fsym string, tsyms string) Price {
    url := fmt.Sprintf("https://min-api.cryptocompare.com/data/price?fsym=" + fsym + "&tsyms=" + tsyms)

    fmt.Println("Requesting data from " + url)

    price := Price{}

    // getting the data using http
    request, err := http.Get(url)
    if err != nil {
        log.Fatal(err.Error())
    }

    // Read the response body using ioutil
    body, err := ioutil.ReadAll(request.Body)
    if err != nil {
        log.Fatal(err.Error())
    }

    defer request.Body.Close()

    if request.StatusCode == http.StatusOK {
        json.Unmarshal(body, &price)
    }

    return price

}

At the moment all I receive is an empty struct, I know the link is bringing back the correct data and I've tested it in my browser.

Answer 1

The mapping doesn't work that way. Instead, you should use a map:

    data := []byte(`{
       "GBP": 657.54
     }`)

    priceMap := map[string]float64{}
    err := json.Unmarshal(data, &priceMap)
    // Check your errors!
    if err != nil {
      log.Fatal(err.Error())
    }
    fmt.Println(priceMap)

This will print:

map[GBP:657.54]

You can then iterate over the map and build the struct you mentioned above, or just access the entry directly if you know the currency. eg: priceMap["GBP"]

You should really check your errors, especially if you're not getting the output you expect from Unmarshal.