CODEWITHSUNDEEP
go
BitQueen
BitQueen

Reputation: 815

Go - access struct property by index

Is it possible in go to access a struct property by its index?

For example when I have a struct of Type Person {name string, age int}

and I have a function with an index parameter, I want to be able to get the age of that struct if the index is 1 or the name if the index is 0.

I tried something like that in my code but it is not working with the error that it can not be indexed.

func filterOHLCV(candles []*binance.Kline, index OHLCV_INDEX) []float64 {
close := []float64{}
for _, c := range candles {
    closePrice, err := strconv.ParseFloat(c[index], 64)
    if err != nil {
        fmt.Print(err)
    }
    close = append(close, closePrice)}

return close

Upvotes: 1

Views: 860

Answers (1)

AMK
AMK

Reputation: 836

As mentioned by @icza, you can use reflection, but you can simply achieve what you want by using a mapper, which is safer and cleaner like:

type MyIndex int

const (
    NameIndex MyIndex = iota
    AgeIndex
    // Other properties here
)

type Person struct {
    name string
    age  int
}

func filterPersonProperty(persons []Person, index MyIndex) []interface{} {
    result := []interface{}{}
    for _, p := range persons {
        if index == NameIndex {
            result = append(result, p.name)
        } else if index == AgeIndex {
            result = append(result, p.age)
        }
    }
    return result
}

func main() {
    persons := []Person{
        {name: "Alice", age: 30},
        {name: "Bob", age: 25},
    }

    index := AgeIndex

    properties := filterPersonProperty(persons, index)
    fmt.Println(properties)
}

If you want to use reflection:

p := Person{Name: "Alice", Age: 30}
index := []int{0} // 0 for Name, 1 for Age

value := reflect.ValueOf(p)
fieldValue := value.FieldByIndex(index)

fmt.Println(fieldValue.Interface())

Upvotes: 4

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