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Swift is modern, type-safe, expressive, performant
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but Objective-C remains a first-class citizen
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Same design patterns, Cocoa APIs
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"We do not want you to rewrite or stop improving your existing code!"
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Should you use
unowned
orweak
for delegates? -
To expose Objective-C to Swift, use a bridging header
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import Foundation | |
infix operator | {} | |
func | (lhs: String, rhs: String) -> String { | |
return NSLocalizedString(lhs, comment: rhs) | |
} | |
postfix operator | {} | |
postfix func | (s: String) -> String { | |
return NSLocalizedString(s, comment: "") | |
} |
- A value of class type in Swift is never nil
var fileModificationDate: NSDate!
- Objective-C does not have a notion of a "never-nil" pointer
!
is an implicitly unwrapped optional- can be tested explicitly for nil
- can directly access properties/methods of the underlying value
- can be implicitly converted to its underlying value
WWDC 2014 Brain Lanier
- Cleaner alternative to using sentinels (
NULL
,NSNotFound
, etc.) to represent invalid values - optionals are initialized to nil by default
var optionalNumber: Int?
nil
is a sentinel value that works with any type- value is wrapped in optional by setter
optionalNumber = 6
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