Daniel Jalkut's performance at the dotSwift 2019 conference in Paris, France.

1. Just Enough
Objective-C
Daniel Jalkut
Red Sweater Software

2. Pure Swift

3. import UIKit
class ViewController: UIViewController {
override func viewDidAppear(_ animated: Bool) {
super.viewDidAppear(animated)
let myAlert = UIAlertController(title: "Hello Objective-C",
message: "It's nice to meet you.",
preferredStyle: .alert)
self.present(myAlert, animated: true, completion: nil)
}
}

4. import UIKit
class ViewController: UIViewController {
override func viewDidAppear(_ animated: Bool) {
super.viewDidAppear(animated)
let myAlert = UIAlertController(title: "Hello Objective-C",
message: "It's nice to meet you.",
preferredStyle: .alert)
self.present(myAlert, animated: true, completion: nil)
}
}

6. Open Your
Ears

7. Symbol: objc_msgSend
Action: x/s $arg2

9. 150,000+ Calls

10. objc_msgSend

11. opensource.apple.com

12. ENTRY _objc_msgSend
UNWIND _objc_msgSend, NoFrame
cmp p0, #0 // nil check and tagged pointer check
#if SUPPORT_TAGGED_POINTERS
b.leLNilOrTagged // (MSB tagged pointer looks negative)
#else
b.eqLReturnZero
#endif
ldr p13, [x0] // p13 = isa
GetClassFromIsa_p16 p13 // p16 = class
LGetIsaDone:
CacheLookup NORMAL // calls imp or objc_msgSend_uncached
#if SUPPORT_TAGGED_POINTERS
LNilOrTagged:
b.eqLReturnZero // nil check
// tagged
adrpx10, _objc_debug_taggedpointer_classes@PAGE
add x10, x10, _objc_debug_taggedpointer_classes@PAGEOFF
ubfxx11, x0, #60, #4
ldr x16, [x10, x11, LSL #3]
adrpx10, _OBJC_CLASS_$___NSUnrecognizedTaggedPointer@PAGE
add x10, x10, _OBJC_CLASS_$___NSUnrecognizedTaggedPointer@PAGEOFF
cmp x10, x16
b.neLGetIsaDone
// ext tagged
adrpx10, _objc_debug_taggedpointer_ext_classes@PAGE
add x10, x10, _objc_debug_taggedpointer_ext_classes@PAGEOFF
ubfxx11, x0, #52, #8
ldr x16, [x10, x11, LSL #3]
b LGetIsaDone
// SUPPORT_TAGGED_POINTERS
#endif
LReturnZero:
// x0 is already zero
mov x1, #0
movid0, #0
movid1, #0
movid2, #0
movid3, #0
ret
END_ENTRY _objc_msgSend

13. Method
Selectors
Are Just Strings!

14. "insertObject:atIndex:"

15. "insertObject:atIndex:"
[anArray insertObject:anObj atIndex:0];
ojc_msgSend(anArray, “insertObject:atIndex:”,
anObj, 0);

16. 0x7fff51e26db0
anArray.insert("Hi", atIndex:0)
Swift 0x7fff51e26db0
(anArray, ”Hi", 0)
Obj-C
[anArray insertObject:@"Hi" atIndex:0];
objc_msgSend(anArray,“insertObject:atIndex:”,
@“Hi”, 0);
0x7fff51e26db0
(anArray, @”Hi”, 0)

17. Who Cares?

18. @objc

19. Implicitly @objc
Override of ObjC Method
@IBAction Method
ObjC Protocol Conformance

20. import UIKit
class ViewController: UIViewController {
override func viewDidAppear(_ animated: Bool) {
super.viewDidAppear(animated)
let myAlert = UIAlertController(title: "Hello Objective-C",
message: "It's nice to meet you.",
preferredStyle: .alert)
self.present(myAlert, animated: true, completion: nil)
}
}

22. @objc(theSky:reallyIs:theLimit:here:)

23. Namespace
Collision Protection
extension UIView {
func fancyMethod() {
// Do something you wish UIView did
}
}

24. Namespace
Collision Protection
extension UIView {
@objc(redSweater_FancyMethod)
func fancyMethod() {
// Do something you wish UIView did
}
}

25. Outgoing
Calls

26. override func viewDidAppear(_ animated: Bool) {
super.viewDidAppear(animated)
let myAlert = UIAlertController(title: "Hello Objective-C",
message: "It's nice to meet you.",
preferredStyle: .alert)
self.present(myAlert, animated: true, completion: nil)
}

28. self.present(myAlert, animated: true, completion: nil)

29. Calling Private
Methods
override func viewDidAppear(_ animated: Bool) {
super.viewDidAppear(animated)
let viewHierarchy = self.view.recursiveDescription
NSLog("My view hierarchy: (viewHierarchy)")
}

30. Calling Private
Methods
override func viewDidAppear(_ animated: Bool) {
super.viewDidAppear(animated)
let viewHierarchy = self.view.perform("recursiveDescription")
NSLog("My view hierarchy: (viewHierarchy)")
}
2019-01-1 17:48:49.573485-0500 Hello Objective-C[53659:310326] My view hierarchy: Optional(Swift.Unmanaged<Swift.AnyObject>(_value: <UIView:
0x7fa836c0dc50; frame = (0 0; 414 896); autoresize = W+H; layer = <CALayer: 0x600001145ba0>>
| <UIImageView: 0x7fa836c0de30; frame = (0 44; 414 818); autoresize = RM+BM; userInteractionEnabled = NO; layer = <CALayer: 0x600001145bc0>>
| <UIButton: 0x7fa836c014a0; frame = (107.5 594; 199 231); opaque = NO; autoresize = RM+BM; layer = <CALayer: 0x600001145720>>
| | <UIButtonLabel: 0x7fa838804310; frame = (0.5 91.5; 198.5 48); text = 'Show Panel'; opaque = NO; userInteractionEnabled = NO; layer =
<_UILabelLayer: 0x60000322fcf0>>))

31. Bridging
Headers
Import ObjC Interfaces
Available Everywhere
Simplify Call Site Code

32. Bridging
Headers
override func viewDidAppear(_ animated: Bool) {
super.viewDidAppear(animated)
let viewHierarchy = self.view.recursiveDescription
NSLog("My view hierarchy: (viewHierarchy)")
}

33. //
// Use this file to import your target's public headers that you
// would like to expose to Swift.
//
#import <UIKit/UIKit.h>
#if DEBUG
@interface UIView (RSDebugging)
// Expose private UIView debugging method to Swift
@property (readonly) NSString* recursiveDescription;
@end
#endif

34. override func viewDidAppear(_ animated: Bool) {
super.viewDidAppear(animated)
let viewHierarchy = self.view.recursiveDescription
NSLog("My view hierarchy: (viewHierarchy)")
}
2019-01-1 17:48:49.573485-0500 Hello Objective-C[53659:310326] My view hierarchy: Optional(Swift.Unmanaged<Swift.AnyObject>(_value: <UIView:
0x7fa836c0dc50; frame = (0 0; 414 896); autoresize = W+H; layer = <CALayer: 0x600001145ba0>>
| <UIImageView: 0x7fa836c0de30; frame = (0 44; 414 818); autoresize = RM+BM; userInteractionEnabled = NO; layer = <CALayer: 0x600001145bc0>>
| <UIButton: 0x7fa836c014a0; frame = (107.5 594; 199 231); opaque = NO; autoresize = RM+BM; layer = <CALayer: 0x600001145720>>
| | <UIButtonLabel: 0x7fa838804310; frame = (0.5 91.5; 198.5 48); text = 'Show Panel'; opaque = NO; userInteractionEnabled = NO; layer =
<_UILabelLayer: 0x60000322fcf0>>))

35. This One
Weird Trick

36. import UIKit
class ViewController: UIViewController {
override func viewDidAppear(_ animated: Bool) {
super.viewDidAppear(animated)
let myAlert = UIAlertController(title: "Hello Objective-C",
message: "It's nice to meet you.",
preferredStyle: .alert)
self.present(myAlert, animated: true, completion: nil)
}
}
self.present(myAlert, animated: true, completion: nil)

37. (lldb) b UIViewController.present(_: __C.UIViewController, animated:
Swift.Bool, completion: Swift.Optional<() -> ()>
self.present(myAlert, animated: true, completion: nil)
Breakpoint 10: no locations (pending).
WARNING: Unable to resolve breakpoint to any actual locations.

38. self.present(myAlert, animated: true, completion: nil)
(lldb) break set -r UIView.*present.*anim.*comp
Breakpoint 1: 8 locations.
(lldb) break list
(lldb) break set -r “-[.*]" // 270K breakpoints!
(lldb) break set -r DebugMode
(lldb) break set -r Emoji
UIKitCore`-[UIViewController presentViewController:animated:completion:]

39. Pure Swift

40. Learn More
WWDC 2011 #322
WWDC 2015 #401
Swift Reference: Attributes

41. WWDC 2011 #322
WWDC 2015 #401
Swift Reference: Attributes
Thank you!