How to create array of unique object list in Swift

As of Swift 1.2 (Xcode 6.3 beta), Swift has a native set type. From the release notes:

A new Set data structure is included which provides a generic collection of unique elements, with full value semantics. It bridges with NSSet, providing functionality analogous to Array and Dictionary.

Here are some simple usage examples:

// Create set from array literal:
var set = Set([1, 2, 3, 2, 1])

// Add single elements:
set.insert(4)
set.insert(3)

// Add multiple elements:
set.unionInPlace([ 4, 5, 6 ])
// Swift 3: set.formUnion([ 4, 5, 6 ])

// Remove single element:
set.remove(2)

// Remove multiple elements:
set.subtractInPlace([ 6, 7 ])
// Swift 3: set.subtract([ 6, 7 ])

print(set) // [5, 3, 1, 4]

// Test membership:
if set.contains(5) {
    print("yes")
}

but there are far more methods available.

Update: Sets are now also documented in the "Collection Types" chapter of the Swift documentation.

You can use any Objective-C class in Swift:

var set = NSMutableSet()
set.addObject(foo)