As of Swift 2.0, you don't need to write your own extension to filter nil values from an Array, you can use flatMap, which flattens the Array and filters nils:
let optionals : [String?] = ["a", "b", nil, "d"]
let nonOptionals = optionals.flatMap{$0}
print(nonOptionals)
let optionals : [String?] = ["a", "b", nil, "d"]
let nonOptionals = optionals.flatMap{$0}
print(nonOptionals)
let optionals : [String?] = ["a", "b", nil, "d"]
let nonOptionals = optionals.flatMap{$0}
print(nonOptionals)
Prints:
[a, b, d]
[a, b, d]
[a, b, d]