Comparing two enum variables regardless of their associated values - swift

Question

Consider this enum:
enum DataType {
case One (data: Int)
case Two (value: String)
}
Swift has pattern matching to compare an enum with associated values, like so:
let var1 = DataType.One(data: 123)
let var2 = DataType.One(data: 456)
if case DataType.One(data: _) = var2 {
print ("var2 is DataType.One")
}
How would one go about comparing not one variable against an enum type, but comparing the enum type of two variables? I saw a ton of similar questions, but none focused on the case where you have two variables.
What I basically want is:
if case var1 = var2 {
print ("var1 is the same enum type as var2")
}

Answer 1

Updated approach:
I think there's no native support for this. But you can achieve it by defining a custom operator (preferrably by using a protocol, but you can do it directly as well). Something like this:
protocol EnumTypeEquatable {
static func ~=(lhs: Self, rhs: Self) -> Bool
}
extension DataType: EnumTypeEquatable {
static func ~=(lhs: DataType, rhs: DataType) -> Bool {
switch (lhs, rhs) {
case (.one, .one),
(.two, .two):
return true
default:
return false
}
}
}
And then use it like:
let isTypeEqual = DataType.One(value: 1) ~= DataType.One(value: 2)
print (isTypeEqual) // true
Old approach:
protocol EnumTypeEquatable {
var enumCaseIdentifier: String { get }
}
extension DataType: EnumTypeEquatable {
var enumCaseIdentifier: String {
switch self {
case .one: return "ONE"
case .two: return "TWO"
}
}
}
func ~=<T>(lhs: T, rhs: T) -> Bool where T: EnumTypeEquatable {
return lhs.enumCaseIdentifier == rhs.enumCaseIdentifier
}
The older version depends on Runtime and might be provided with default enumCaseIdentifier implementation depending on String(describing: self) which is not recommended. (since String(describing: self) is working with CustromStringConvertible protocol and can be altered)

Answer 2

Just confirm to Equatable like below
extension DataType: Equatable {
static func == (lhs: DataType, rhs: DataType) -> Bool {
switch (lhs, rhs) {
case (.One, .Two), (.Two, .One):
return false
case (.One, .One), (.Two, .Two):
return true
}
}
}
If you don't want to implement Equatable just move content into instance method:
extension DataType{
func isSame(_ other: DataType) -> Bool {
switch (self, other) {
case (.One, .Two), (.Two, .One):
return false
case (.One, .One), (.Two, .Two):
return true
}
}
}
Use:
let isTypeEqual = DataType.One(value: 1).isSame(DataType.One(value: 2))
print (isTypeEqual) // true

Answer 3

This worked for me:
enum DataType {
case one (data: Int)
case two (value: String)
}
protocol EnumTypeEquatable {
static func sameType(lhs: Self, rhs: Self) -> Bool
}
extension DataType: EnumTypeEquatable {
static func sameType(lhs: DataType, rhs: DataType) -> Bool {
if let caseLhs = Mirror(reflecting: lhs).children.first?.label, let caseRhs = Mirror(reflecting: rhs).children.first?.label {
return (caseLhs == caseRhs)
} else { return false }
}
}
let isTypeEqual = DataType.sameType(lhs: .one(data: 1), rhs: .one(data: 2))
print (isTypeEqual) // true