Swift 2.0 : ‘enumerate’ is unavailable: call the ‘enumerate()’ method on the sequence

Many global functions have been replaced by protocol extension methods,
a new feature of Swift 2, so enumerate() is now an extension method
for SequenceType:

extension SequenceType {
    func enumerate() -> EnumerateSequence<Self>
}

and used as

let mySwiftStringArray = [ "foo", "bar" ]
for (index, string) in mySwiftStringArray.enumerate() {
   print(string) 
}

And String does no longer conform to SequenceType, you have to
use the characters property to get the collection of Unicode
characters. Also, count() is a protocol extension method of
CollectionType instead of a global function:

let myString = "foo"
let stringLength = myString.characters.count
print(stringLength)

Update for Swift 3: enumerate() has been renamed to enumerated():

let mySwiftStringArray = [ "foo", "bar" ]
for (index, string) in mySwiftStringArray.enumerated() {
    print(string)
}