检查枚举中是否存在值

Question

I have created a strict like the following in my app:

type Datatype int8

const (
    user Datatype = iota
    address
    test
)

var datatypes = [...]string{"User", "Address", "Test"}

func (datatype Datatype) String() string {
    return datatypes[datatype]
}

I would like to be able to validate a value passed via a command-line flag against this enum.

I thought I had seen something like dtype == Datatype being used, but I am apparently sorely mistaken.

If this is not possible I can go the route of putting these values in an array. However, I feel the enum approach is more elegant.

Answer 1

From your code sample it looks like you are trying to see if a map (rather than a struct) contains a particular key.

If so, the answer is here

A two-value assignment tests for the existence of a key:

i, ok := m["route"] 

In this statement, the first value (i) is assigned the value stored under the key "route". If that key doesn't exist, i is the value type's zero value (0). The second value (ok) is a bool that is true if the key exists in the map, and false if not.

To test for a key without retrieving the value, use an underscore in place of the first value:

_, ok := m["route"]