https://www.youtube.com/watch?v=VNmtmz3mJN4& Deep dive into InjectionTDD - how to perform iOS unit tests realtime, without rebuilding entire Xcode project.

1. Live-updating Swift
code
Bartosz Polaczyk

2. Senior iOS Developer
Bartosz Polaczyk

3. Agenda
• Demo
• How does Injection work?
• Swift limitations

4. Demo
Injection for Xcode®

5. Runtime
Live code injection ObjC

6. Runtime
Live code injection ObjC
Injection
Bundle

7. Runtime
Live code injection ObjC
Injection
Bundle

8. Method swizzling
let selectorToReplace = #selector(methodName)
let originalMethod = class_getInstanceMethod(UIView.self, selectorToReplace)
let swizzledMethod = class_getInstanceMethod(OtherClass.self, selectorToReplace)
method_exchangeImplementations(originalMethod, swizzledMethod)

9. Method swizzling
let selectorToReplace = #selector(methodName)
let originalMethod = class_getInstanceMethod(UIView.self, selectorTo
let swizzledMethod = class_getInstanceMethod(OtherClass.self, select
method_exchangeImplementations(originalMethod, swizzledMethod)

10. Runtime
Live code injection ObjC

11. Injection
Bundle
Runtime
Live code injection ObjC

12. Injection
Bundle
Runtime
Live code injection ObjC

13. Dispatching in Swift

14. Dispatching in Swift

15. Swift class memory layout
class(isa)
…
…
Method 1
Method 2
Method 3
…

16. Swift class memory layout
class(isa)
…
…
Method 1
Method 2
Method 3
…
pushq %rbp
movq %rsp, %rbp
pushq %r13
subq $0x38, %rsp
movq %r12, %rcx
movq 0x10(%r13), %rdi
movq 0x18(%r13), %rdx
movq %rdi, -0x10(%rbp)
movq %rdx, %rdi

17. Swift class memory layout
class(isa)
…
…
Method 1
Method 2
Method 3
…
pushq %rbp
movq %rsp, %rbp
pushq %r13
subq $0x38, %rsp
movq %r12, %rcx
movq 0x10(%r13), %rdi
movq 0x18(%r13), %rdx
movq %rdi, -0x10(%rbp)
movq %rdx, %rdi
pushq %rbp
movq %rsp, %rbp
pushq %r14
subq $0x38, %rsp
movq %r11, %rcx
movq 0x10(%r13), %rdi
movq 0x18(%r13), %rdx
movq %rdi, -0x10(%rbp)
movq %rdx, %rdi

18. Swift class memory layout
class(isa)
…
…
Method 1
Method 2
Method 3
…
pushq %rbp
movq %rsp, %rbp
pushq %r13
subq $0x38, %rsp
movq %r12, %rcx
movq 0x10(%r13), %rdi
movq 0x18(%r13), %rdx
movq %rdi, -0x10(%rbp)
movq %rdx, %rdi
pushq %rbp
movq %rsp, %rbp
pushq %r14
subq $0x38, %rsp
movq %r11, %rcx
movq 0x10(%r13), %rdi
movq 0x18(%r13), %rdx
movq %rdi, -0x10(%rbp)
movq %rdx, %rdi

19. Swift vtable copy
// if swift language class, copy vtable
struct _in_objc_class *newclass = (struct _in_objc_class *)INJECTION_BRIDGE(void *)newClass;
if ( (uintptr_t)newclass->internal & 0x1 ) {
struct _in_objc_class *oldclass = (struct _in_objc_class *)INJECTION_BRIDGE(void *)oldClass;
size_t bytes = oldclass->mdsize - offsetof(struct _in_objc_class, dispatch) - 2*sizeof(IMP);
memcpy( oldclass->dispatch, newclass->dispatch, bytes );
}

20. Swift vtable copy
// if swift language class, copy vtable
struct _in_objc_class *newclass = (struct _in_ob
if ( (uintptr_t)newclass->internal & 0x1 ) {
struct _in_objc_class *oldclass = (struct _i
size_t bytes = oldclass->mdsize - offsetof(s
memcpy( oldclass->dispatch, newclass->dispat
}

21. Static dispatch
class
struct

22. Static dispatch
class
struct

23. Static dispatch
class
struct

24. InjectionForXcode Swift
limitations

25. InjectionForXcode Swift
limitations
• classes inherit from NSObject

26. InjectionForXcode Swift
limitations
• classes inherit from NSObject
• non-final classes

27. InjectionForXcode Swift
limitations
• classes inherit from NSObject
• non-final classes
• non-final methods

28. InjectionForXcode Swift
limitations
• classes inherit from NSObject
• non-final classes
• non-final methods
• no structs/enums, no extensions

29. InjectionForXcode Swift
limitations
• classes inherit from NSObject
• non-final classes
• non-final methods
• no structs/enums, no extensions
• no global functions

30. InjectionForXcode Swift
limitations
• classes inherit from NSObject
• non-final classes
• non-final methods
• no structs/enums, no extensions
• no global functions
• no methods/properties added

31. but…

33. InjectionTDD

34. Demo

35. InjectionTDD

36. InjectionTDD
• Live unit tests

37. InjectionTDD
• Live unit tests
• Zero configuration

38. InjectionTDD
• Live unit tests
• Zero configuration
• CocoaPods or .framework integration

39. InjectionTDD
• Live unit tests
• Zero configuration
• CocoaPods or .framework integration
• Standard Xcode interface

40. InjectionTDD
• Live unit tests
• Zero configuration
• CocoaPods or .framework integration
• Standard Xcode interface
• Swift only

41. build.log
build.log
build.logbuild.log
lldb
simulator

42. build.log
build.log
build.logbuild.log
lldb
simulator

43. build.log
build.log
build.logbuild.log
lldb
simulator
1
lldb

44. build.log
build.log
build.logbuild.log
lldb
simulator
1
lldb
TCP
socket
2

45. build.log
build.log
build.logbuild.log
lldb
simulator
TCP
socket
2

46. build.log
build.log
build.logbuild.log
lldb
simulator
3
TCP
socket
2

47. build.log
build.log
build.logbuild.log
lldb
simulator
TCP
socket
2

48. build.log
build.log
build.logbuild.log
lldb
simulator
TCP
socket
2
4

49. build.log
build.log
build.logbuild.log
lldb
simulator
TCP
socket
2

50. build.log
build.log
build.logbuild.log
lldb
simulator
TCP
socket
2
5

51. swiftc/swift
InjectionBundle

52. swiftc/swift
file1.o
file2.o
file3.o
InjectionBundle

53. swiftc/swift
file1.o
file2.o
file3.o
InjectionBundle

54. class
struct

55. class
struct
class
struct

56. file .swiftdeps

57. file .swiftdeps
## Swift dependencies file v0 ###
provides-top-level:
- "TrackingClientType"
provides-nominal:
- "7Library18TrackingClientTypeP"
provides-member:
- ["7Library18TrackingClientTypeP", ""]
- ["7Library18TrackingClientTypeP", "track"]
provides-dynamic-lookup:
depends-top-level:
- !private "!"
- !private "!="
...
- !private ["13ReactiveSwift14SignalProducerV", "uniqueValues"]
- !private ["13ReactiveSwift22SignalProducerProtocolP", "collect"]
- !private ["13ReactiveSwift22SignalProducerProtocolP", "concat"]
- !private ["13ReactiveSwift22SignalProducerProtocolP", "demoteErrors"]
- !private ["13ReactiveSwift22SignalProducerProtocolP", "filter"]
- !private ["13ReactiveSwift22SignalProducerProtocolP", "ksr_delay"]
- !private ["13ReactiveSwift22SignalProducerProtocolP", "map"]
- !private ["13ReactiveSwift22SignalProducerProtocolP", "take"]
- !private ["13ReactiveSwift22SignalProducerProtocolP", "uncollect"]
- !private ["13ReactiveSwift22SignalProducerProtocolP", "uniqueValues"]
- !private ["13ReactiveSwift14SignalProtocolP", "combineLatest"]
- !private ["13ReactiveSwift14SignalProtocolP", "filter"]
- !private ["13ReactiveSwift14SignalProtocolP", "flatMap"]
- !private ["13ReactiveSwift14SignalProtocolP", "ignoreValues"]
...

58. file .swiftdeps
- "TrackingClientType"
provides-nominal:
- "7Library18TrackingClientTypeP"
provides-member:
- ["7Library18TrackingClientTypeP", ""]
- ["7Library18TrackingClientTypeP", "track"]
provides-dynamic-lookup:
depends-top-level:
- !private "!"
- !private "!="
...
- !private ["13ReactiveSwift14SignalProducerV", "uniqueVal
- !private ["13ReactiveSwift22SignalProducerProtocolP", "c
- !private ["13ReactiveSwift22SignalProducerProtocolP", "c
- !private ["13ReactiveSwift22SignalProducerProtocolP", "d
- !private ["13ReactiveSwift22SignalProducerProtocolP", "f
- !private ["13ReactiveSwift22SignalProducerProtocolP", "k
- !private ["13ReactiveSwift22SignalProducerProtocolP", "m

59. InjectionTDD limitations

60. InjectionTDD limitations
• No Objective-C

61. InjectionTDD limitations
• No Objective-C
• No static libraries used

62. InjectionTDD limitations
• No Objective-C
• No static libraries used
• Host application

63. InjectionTDD limitations
• No Objective-C
• No static libraries used
• Host application
• ⌘+U, if new file added

64. Installation
• Download Injection For Xcode with TDD
• correct xcode-select -p
• Integrate InjectionTDD to your project
• e.g. pod 'InjectionTDD', '~> 0.4’
• ⌘+U

65. Optionally: install Xcode
breakpoints

66. Optionally: install Xcode
breakpoints
curl https://codeload.github.com/polac24/InjectionTDD/tar.gz/master | tar -xz --strip=3
InjectionTDD-master/scripts/update_breakpoints_source/
./update_breakpoints_source.sh

67. Summary
• Injection For Xcode for UI
• InjectionTDD for unit tests
• tests on ⌘+S
• Swift
• minimal configuration
• standard Xcode interface

68. References
• InjectionTDD: https://github.com/polac24/InjectionTDD
• Download Injection: http://johnholdsworth.com/
injection.html
• Method Dispatch in Swift: https://www.raizlabs.com/dev/
2016/12/swift-method-dispatch/
• Exploring Swift Memory Layout • Mike Ash: https://
www.youtube.com/watch?v=ERYNyrfXjlg

69. Q&A