How to check variable type at runtime in Go language
It seems that Go have special form of switch dedicate to this (it is called type switch):
func (e *Easy)SetOption(option Option, param interface{}) {
switch v := param.(type) {
default:
fmt.Printf("unexpected type %T", v)
case uint64:
e.code = Code(C.curl_wrapper_easy_setopt_long(e.curl, C.CURLoption(option), C.long(v)))
case string:
e.code = Code(C.curl_wrapper_easy_setopt_str(e.curl, C.CURLoption(option), C.CString(v)))
}
}
The answer by @Darius is the most idiomatic (and probably more performant) method. One limitation is that the type you are checking has to be of type interface{}
. If you use a concrete type it will fail.
An alternative way to determine the type of something at run-time, including concrete types, is to use the Go reflect
package. Chaining TypeOf(x).Kind()
together you can get a reflect.Kind
value which is a uint
type: http://golang.org/pkg/reflect/#Kind
You can then do checks for types outside of a switch block, like so:
import (
"fmt"
"reflect"
)
// ....
x := 42
y := float32(43.3)
z := "hello"
xt := reflect.TypeOf(x).Kind()
yt := reflect.TypeOf(y).Kind()
zt := reflect.TypeOf(z).Kind()
fmt.Printf("%T: %s\n", xt, xt)
fmt.Printf("%T: %s\n", yt, yt)
fmt.Printf("%T: %s\n", zt, zt)
if xt == reflect.Int {
println(">> x is int")
}
if yt == reflect.Float32 {
println(">> y is float32")
}
if zt == reflect.String {
println(">> z is string")
}
Which prints outs:
reflect.Kind: int
reflect.Kind: float32
reflect.Kind: string
>> x is int
>> y is float32
>> z is string
Again, this is probably not the preferred way to do it, but it's good to know alternative options.