Golang - Comparison operator not defined on interface converted to float64

Question

As shown in the code below, I'm doing some type switching on an interface{} in order to do the correct type switching - I'm trying to convert the interface{} to either a float64 or a string and then comparing it to a value, however, when using a comparison operator other than == on the float64's, Go complains about it when building.

The errors Go spits out are as follows :-

invalid operation: (interface {})(val.(float64)) > subval.Value (operator > not defined on interface)
invalid operation: (interface {})(val.(float64)) >= subval.Value (operator >= not defined on interface)
invalid operation: (interface {})(val.(float64)) < subval.Value (operator < not defined on interface)
invalid operation: (interface {})(val.(float64)) <= subval.Value (operator <= not defined on interface)

...and this is my code:-

val:= s.FieldByName(subval.Metric).Interface()
switch val(type) {
case float64, float32, int:
    switch subval.Type {
    case "greater_than":
        if val.(float64) > subval.Value {
            runAction(subval.Action, Config)
        }
    case "greater_than_or_equal_to":
        if val.(float64) >= subval.Value {
            runAction(subval.Action, Config)
        }
    case "equal_to":
        if val.(float64) == subval.Value {
            runAction(subval.Action, Config)
        }
    case "less_than":
        if val.(float64) < subval.Value {
            runAction(subval.Action, Config)
        }
    case "less_than_or_equal_to":
        if val.(float64) <= subval.Value {
            runAction(subval.Action, Config)
        }
    }
case string:
    if subval.Type == "equal_to" {
        if val.(string) == subval.Value {
            runAction(subval.Action, Config)
        }
    }
}

Answer 1

Your problem is probably that subval.Value is an interface{}, so the comparison operator isn't available. I think that when doing an equality comparison with an interface, go compare the underlying types byte-wise, hence the == not giving an error.