Do Enums in Dart have comparison operators? - dart

Question

I come from a Kotlin background and I used to the fact that enums there implements Comparable, which allows me do something like below:
Given a enum
enum class Fruit{
APPLE,
BANANA,
ORANGE,
}
I could use the operators <, >, <= or >=, to compare any occurrence of this enum, like:
APPLE < BANANA -> true
ORANGE < BANANA -> false
I wonder if dart has the same by default or if I have to define custom operators to any enum I might need that.

Answer 1

It's easy to check Enum documentation or try it yourself to see that Enum classes do not provide operator <, operator >, etc.
Dart 2.15 does add an Enum.compareByIndex method, and you also can add extension methods to Enums:
extension EnumComparisonOperators on Enum {
bool operator <(Enum other) {
return index < other.index;
}
bool operator <=(Enum other) {
return index <= other.index;
}
bool operator >(Enum other) {
return index > other.index;
}
bool operator >=(Enum other) {
return index >= other.index;
}
}

Answer 2

As explained in other comments, you can also create your own operator and use it.
Try the code below to see how to handle it without creating an operator.
enum Fruit{
APPLE,
BANANA,
ORANGE,
}
void main() {
print(Fruit.APPLE.index == 0);
print(Fruit.BANANA.index == 1);
print(Fruit.ORANGE.index == 2);
if( Fruit.APPLE.index < Fruit.BANANA.index ){
// Write your code here
print("Example");
}
}
result
true
true
true
Example

Answer 3

Since 2.15, statically:
compareByIndex<T extends Enum>(T value1, T value2) → int
Compares two enum values by their index. [...]
#Since("2.15")
compareByName<T extends Enum>(T value1, T value2) → int
Compares enum values by name. [...]
#Since("2.15")
https://api.dart.dev/stable/2.16.1/dart-core/Enum-class.html