如何在golang中检查值是否为iota常数类型？

Question

I have a following type defined using iota in golang.

type StatusType int

const (
    PENDING StatusType = iota
    APPROVED
    REJECTED
)

I want to restrict the value passed in in REST-API to the StatusType. Such that the value should not exceed 0,1,2.

Answer 1

Simply don't export StatusType (assuming you define it in package 'status').
This follow "What is an idiomatic way of representing enums in Go?":

type statusType int

const (
    PENDING statusType = iota
    APPROVED
    REJECTED
)
type StatusTyper interface {
    StatusType() statusType 
}

func(st statusType) StatusType() statusType {
    return st
}

Any external package would then refer to StatusType-like variable as status.PENDING, status.APPROVED or status.REJECTED.
(the only three statusType which implement the StatusTyper interface. Caveat applies.)