Is it possible to know the type of return value of a function in Go?

go

Solution

Rather than using `reflect.ValueOf(f)` try `reflect.TypeOf(f)`. The `Type` type has two relevant methods named `NumOut` and `Out(int)`. To get the types of all return values in order, you can use the following loop

typ := reflect.TypeOf(f)

for i := 0; i < typ.NumOut(); i++ {
    returnType := typ.Out(i)
    // do something with returnType
}

If you're certain your function only has one return value, you can always get it with `Out(0)`, the standard disclaimers about making sure your input is correct apply.

Problem

For example, I want to do something like this, ``` package main import ( "fmt" "reflect" ) func main() { var f func(int) int v := reflect.ValueOf(f) fmt.Println(v.ReturnType() == reflect.TypeOf(1)) // => true } ``` `ReturnType` method doesn't exist in reflect package. My question is, can I implement such a function without using `cgo`.

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