Create an enum from a group of related constants in Go

Question

What is preferred (or right) way to group large number of related constants in the Go language? For example C# and C++ both have enum for this.

Answer 1

const?

const (
    pi = 3.14
    foo = 42
    bar = "hello"
)

Answer 2

There are two options, depending on how the constants will be used.

The first is to create a new type based on int, and declare your constants using this new type, e.g.:

type MyFlag int

const (
    Foo MyFlag = 1
    Bar
)

Foo and Bar will have type MyFlag. If you want to extract the int value back from a MyFlag, you need a type coersion:

var i int = int( Bar )

If this is inconvenient, use newacct's suggestion of a bare const block:

const (
    Foo = 1
    Bar = 2
)

Foo and Bar are perfect constants that can be assigned to int, float, etc.

This is covered in Effective Go in the Constants section. See also the discussion of the iota keyword for auto-assignment of values like C/C++.