How to get all constants of a type in Go

If your constants are all in an order, you can use this:

type T int

const (
    TA T = iota
    TB
    TC
    NumT
)

func AllTs() []T {
    ts := make([]T, NumT)
    for i := 0; i < int(NumT); i++ {
        ts[i] = T(i)
    }
    return ts
}

You can also cache the output in e.g. init(). This will only work when all constants are initialised with iota in order. If you need something that works for all cases, use an explicit slice.

There is no way to do this at runtime, as the reflect package cannot be used for it. You could define a list:

const(
    Created State = iota
    Modified
    Deleted
)
var allStates = []State{Created, Modified, Deleted}

You may go further and add in a string representation, or any number of other things.

You may be able to generate such a list from the source to make maintenance easier, but I generally don't think that saves enough time to be worth it. There are tools like stringer that can already do some of that.