Using the Swift if let with logical AND operator &&

As of Swift 1.2, this is now possible. The Swift 1.2 and Xcode 6.3 beta release notes state:

More powerful optional unwrapping with if let — The if let construct
can now unwrap multiple optionals at once, as well as include
intervening boolean conditions. This lets you express conditional
control flow without unnecessary nesting.

With the statement above, the syntax would then be:

if let tabBarController = window!.rootViewController as? UITabBarController where tabBarController.viewControllers.count > 0 {
        println("do stuff")
}

This uses the where clause.

Another example, this time casting AnyObject to Int, unwrapping the optional, and checking that the unwrapped optional meets the condition:

if let w = width as? Int where w < 500
{
    println("success!")
}

For those now using Swift 3, “where” has been replaced by a comma. The equivalent would therefore be:

if let w = width as? Int, w < 500
{
    println("success!")
}