case

An instance method of When class.

func `case`(_ condition: @escaping (Type) -> Bool,  handler: (() -> Result?)? = nil) -> When<Type, Result> 

Get (Type) -> Bool block to be used as a condition. and handler to return the result. Handler block could be omitted to combine several cases

In case of Result is Equtable

extension When where Type: Equatable {
	func `case`(_ condition: Type,  handler: (() -> Result?)? = nil) -> When<Type, Result>
}

Here function takes a value of Type and check if this value is equal to value provided to When in it's constructor.

case returns a self of current When class and could be used as a chain.

...
.case(value){result1}
.case({$0 == something} {result2}
...

The chain needs to be finished with call of default.