This is one of those blog posts which is really just note taking. I’m basically writing this for myself. It may be useful to people who aren’t me.

• 1.2 Grammar: grammar
• 2.0 Beta Grammar: grammar
• Grammar differences: diffs

This exercise doesn’t include stdlib diffs.

Error Handling

Defer, guard, try, throw, do{}, catch statements added for error handling. And throws attribute can be added to function/method declarations.

do {
    defer {print("Done now")}
    guard let x = optionalValue else {
       print("Fail")
       throw NSError(domain: "", code: 0, userInfo: nil)
    }
    print(x) // if not optional
}

Statements

Do-while is now repeat-while, enabling code reading to distinguish difference at the start of the declaration.

repeat {print("Hello")} while false

For in adds where clause (for-in-where)

for i in 0...20 where i % 2 == 1 {
    print("odd: \(i)")
}

While statement and optional binding tweaked but I don’t think people will really notice

New if-case added. The first examples bind the value within the Optional enumeration. The last example uses the new ? operator.

if case .Some(let x) = optionalValue {print("Unwrapped: \(x)")}
if case let .Some(x) = optionalValue {print("Unwrapped: \(x)")}

if case let x? = optionalValue {print("Unwrapped: \(x)")}

For-case

let z : [Int?] = [1, 3, nil, 5, nil]
for case let x? in z {print(x)} // prints 1, 3, 5
for case let .Some(x) in z {print(x)} // prints 1, 3, 5

If statements now support statement labels, added to existing loop and switch constructs.

With regard to parameters, default label behavior has changed and functions now match methods. Hashtag # (internal-external label match) is gone.

Availability

Availability via @available, #available added. Should improve in later betas. Platforms expand from iOS and OSX to include watchOS, iOSApplicationExtension and OSXApplicationExtension.