}
var tos = TOS<String>()
tos.push("Swift")
println(tos.items)tos.push("Generics")
println(tos.items)tos.push("Type Parameters")
println(tos.items)tos.push("Naming Type Parameters")
println(tos.items)extension TOS {
var first: T? {
return items.isEmpty? nil : items[items.count - 1 ]
}
}if let first = tos.first {
println("The top item on the stack is \(first).")
}When we run the above program using playground, we get the following result:
[Swift]
[Swift, Generics]
[Swift, Generics, Type Parameters]
[Swift, Generics, Type Parameters, Naming Type Parameters]The top item on the stack is Naming Type Parameters.
Type Constraints
Swift language allows 'type constraints' to specify whether the type parameter inherits
from a specific class, or to ensure protocol conformance standard.