Check if a slice contains a struct with a given field value

Question

Trying to check if a struct in some slice contains a value of a given field so i wrote this

   func main() {
    //test
    Objs := []Obj{{1,"xxx"},{2,"yyy"},{3,"zzz"}}
    res := containsStructFieldValue(Objs,"X",1)
    fmt.Println(res)
}


type Obj struct {
    X int
    Y string
}

func containsStructFieldValue(slice []Obj ,fieldName string,fieldValueToCheck interface {}) bool{
    for _,s := range slice{
        r := reflect.ValueOf(s)
        f := r.FieldByName(fieldName)
        if f.IsValid(){
            if f.Interface() == fieldValueToCheck{
                return true //a field with the given value exists
            }
        }
    }
    return false
}

i need it to work for any given struct type but when i tried slice []interface as the parameter i found out that its not possible, any idea on how to make the above method work for any struct type?

Answer 1

You can use reflect to range over an interface{}, for instance:

func containsStructFieldValue(slice interface{} ,fieldName string,fieldValueToCheck interface {}) bool{

    rangeOnMe := reflect.ValueOf(slice)

    for i := 0; i < rangeOnMe.Len(); i++ {
        s := rangeOnMe.Index(i)
        f := s.FieldByName(fieldName)
        if f.IsValid(){
            if f.Interface() == fieldValueToCheck {
                return true
            }
        }
    }
}

Note that I did not check that slice is indeed a slice... If not, this code will panic. You can use reflect.Kind to check this if you want to avoid this behaviour.