Swift funtime

An exploration of the new (?) runtime and how the Objective-C runtime API can be used in Swift. Talk given at mobiconf 2014.

Transcript

1. SWIFT FUNTIME MOBICONF 2014 BORIS BÜGLING - @NEONACHO
2. COCOAPODS
3. CONTENTFUL
4. SWIFT
5. AGENDA ▸ How do you even Swift? ▸ What is a Swift object? ▸ Objective-C runtime in the age of Swift ▸ Swift runtime ▸ (some Q&A)
6. “Swift’s clean slate [...] is an opportunity to reimagine how software development works.”
7. ▸ Optionals ▸ Tuples ▸ Generics ▸ Pattern matching ▸ Operator overloading ▸ Namespaces ▸ Type inference ▸ ...
8. EMOJI IDENTIFIERS! ! class ! { func "() { } }
9. INTERFACES WITH C, AT FULL SPEED WATCH "SWIFT AND C" BY MIKE ASH
10. DROPS C++ INTEROPERABILITY
11. Everyone is a Beginner
12. ▸ The Swift Programming Language by  AND ALSO ▸ Swift by Tutorials: A Hands-On Approach ▸ Your First Swift App ▸ Functional Programming in Swift
13. SWIFT COMMAND LINE TOOLS $ xcrun swift Welcome to Swift! Type :help for assistance. $ xcrun swiftc Foo.swift ## will compile an executable $ xcrun swift-stdlib-tool ## assembles libraries for an application bundle $ xcrun swift-demangle _TtCSs29_NativeDictionaryStorageOwner _TtCSs29_NativeDictionaryStorageOwner ---> Swift._NativeDictionaryStorageOwner
14. LET'S DROP CLOSE TO THE METAL
15. WHAT IS A SWIFT OBJECT?
16. IT DEPENDS
17. class MyObject : NSObject { }
18. ▸ behaves like any old Objective-C object ▸ instance variables are properties ▸ fully interopable with ObjC
19. class MyObject { }
20. ▸ has SwiftObject as superclass ▸ instance variables are ivars ▸ ivars have no type encoding ▸ methods are not ObjC methods ▸ not interoperable with ObjC
21. PLAYGROUND! import ObjectiveC.runtime but Playground execution failed: Error in auto-import: failed to get module 'runtime' from AST context (rdar://problem/18482380)
22. !"
23. DEMO: INSPECT OBJECTS
24. SWIFTOBJECT Ivar: magic {SwiftObject_s="isa"^v"refCount"q} Protocol: NSObject NSOBJECT Ivar: isa # Protocol: NSObject
25. class MySwiftClass { var foo = "bar"; init() { } } import Foundation import ObjectiveC.runtime var ivar = class_getInstanceVariable(MySwiftClass().dynamicType, "foo") var value : AnyObject = object_getIvar(MySwiftClass(), ivar)! Segmentation fault: 11
26. #import <Foundation/Foundation.h> #import <objc/runtime.h> @interface MyClass : NSObject @property (nonatomic, retain) NSString* foo; @end #pragma mark - @implementation MyClass -(instancetype)init { self = [super init]; if (self) { self.foo = @"bar"; } return self; } @end #pragma mark - int main(int argc, char *argv[]) { @autoreleasepool { MyClass* object = [MyClass new]; Ivar ivar = class_getInstanceVariable(object.class, "_foo"); id value = object_getIvar(object, ivar); NSLog(@"%@", value); return 0; } }
27. VALUE TYPES SHOULD BE STRUCTS struct MyObject { var a : String var b : Array<Int> }
28. IN PURE SWIFT, THERE'S NO INTROSPECTION !
29. THERE IS HOPE /// How children of this value should be presented in the IDE. enum MirrorDisposition { case Struct case Class case Enum case Tuple [...] } /// A protocol that provides a reflection interface to an underlying value. protocol MirrorType { [...] /// Get the number of logical children this value has. var count: Int { get } subscript (i: Int) -> (String, MirrorType) { get } /// Get a string description of this value. var summary: String { get } [...] }
30. // From: https://gist.github.com/peebsjs/9288f79322ed3119ece4 infix operator --> {} func --> (instance: Any, key: String) -> Any? { let mirror = reflect(instance) for index in 0 ..< mirror.count { let (childKey, childMirror) = mirror[index] if childKey == key { return childMirror.value } } return nil } //Example struct MyPoint { let x: Float let y: Float } let point = MyPoint(x: 1, y: 2) println(point --> "x") println(point --> "y")
31. OBJECTIVE-C RUNTIME IN THE AGE OF SWIFT
32. INHERIT FROM NSObject AND IT JUST WORKS!
33. EVEN SWIZZLING !
34. import Foundation import ObjectiveC.runtime extension NSString { func swizzle_description() -> NSString { return "!" } } var myString = "foobar" as NSString println(myString.description) var originalMethod = class_getInstanceMethod(NSString.self, "description") var swizzledMethod = class_getInstanceMethod(NSString.self, "swizzle_description") method_exchangeImplementations(originalMethod, swizzledMethod) println(myString.description)
37. OR REPLACING METHODS import Foundation import ObjectiveC.runtime let myString = "foobar" as NSString println(myString.description) let myBlock : @objc_block (AnyObject!) -> String = { (sself : AnyObject!) -> (String) in "✋" } let myIMP = imp_implementationWithBlock(unsafeBitCast(myBlock, AnyObject.self)) let method = class_getInstanceMethod(myString.dynamicType, "description") method_setImplementation(method, myIMP) println(myString.description)
38. LET'S TAKE A STEP BACK
39. OBJECTS typedef struct objc_object { Class isa; } *id;
40. CLASSES struct objc_class { Class isa; #if !__OBJC2__ Class super_class OBJC2_UNAVAILABLE; const char *name OBJC2_UNAVAILABLE; long version OBJC2_UNAVAILABLE; long info OBJC2_UNAVAILABLE; long instance_size OBJC2_UNAVAILABLE; struct objc_ivar_list *ivars OBJC2_UNAVAILABLE; struct objc_method_list **methodLists OBJC2_UNAVAILABLE; struct objc_cache *cache OBJC2_UNAVAILABLE; struct objc_protocol_list *protocols OBJC2_UNAVAILABLE; #endif } OBJC2_UNAVAILABLE;
41. OBJECTS ▸ struct magic ▸ contains refCount and isa ▸ methods are in virtual table, like in C++ CLASSES ▸ have mangled names, which contain the module name
42. NAME MANGLING another C++ concept _TFV4test1eCfMS0_FT_S0_ ---> test.e.init (test.e.Type)() -> test.e _TMLCCC4test1a1b1c ---> lazy cache variable for type metadata for test.a.b.c _TMmCCC4test1a1b1c ---> metaclass for test.a.b.c _TMnCC4test1a1b ---> nominal type descriptor for test.a.b _TTWOV4test1e1fSs9EquatableFS2_oi2eeUS2___fMQPS2_FTS3_S3__Sb ---> protocol witness for Swift. Equatable.== infix <A : Swift.Equatable>(Swift.Equatable.Self.Type) (Swift.Equatable.Self, Swift.Equatable.Self) -> Swift.Bool in conformance test.e.f : Swift.Equatable _TWoFC4test1aCfMS0_FT_S0_ ---> witness table offset for test.a.__allocating_init (test.a.Type)() -> test.a _TWoFCCC4test1a1b1c1dfS2_FT1zS0_1xS1_1vFT1xSi_Si_OVS_1e1f ---> witness table offset for test.a.b.c.d (test.a.b.c)(z : test.a, x : test.a.b, v : (x : Swift.Int) -> Swift.Int) -> test.e.f
43. HOW ARE EMOJI FORMED? $ echo 'class ! {}'|xcrun swiftc -emit-library -o test - $ nm -g test ... 0000000000000db0 T __TFC4testX4ypIhD ... $ xcrun swift-demangle __TFC4testX4ypIhD _TFC4testX4ypIhD ---> test.!.__deallocating_deinit X4 ypIh ~ xn--yp8h
44. METHODS struct objc_method { SEL method_name OBJC2_UNAVAILABLE; char *method_types OBJC2_UNAVAILABLE; IMP method_imp OBJC2_UNAVAILABLE; } OBJC2_UNAVAILABLE;
45. METHOD IMPLEMENTATIONS typedef struct objc_selector *SEL; typedef id (*IMP)(id self, SEL _cmd ,...);
46. MESSAGE FORWARDING +(BOOL)resolveInstanceMethod:(SEL)aSEL; -(void)forwardInvocation:(NSInvocation*)anInvocation; -(NSMethodSignature*)methodSignatureForSelector:(SEL)selector; -(BOOL)respondsToSelector:(SEL)aSelector;
47. FROM UIVIEWCONTROLLER.H - (void)attentionClassDumpUser:(id)arg1 yesItsUsAgain:(id)arg2 althoughSwizzlingAndOverridingPrivateMethodsIsFun:(id)arg3 itWasntMuchFunWhenYourAppStoppedWorking:(id)arg4 pleaseRefrainFromDoingSoInTheFutureOkayThanksBye:(id)arg5;
48. CHANGE CLASSES AT RUNTIME ▸ method_setImplementation() ▸ class_addMethod() ▸ ...
49. DEMO: DYNAMIC TABLE VIEW
50. NSINVOCATION DOES NOT EXIST
51. BUT WHAT CAN WE DO ABOUT PURE SWIFT?
52. SWROUTE ▸ PoC of function hooking in Swift ▸ Uses rd_route, a Mach specific injection library for C
53. #include <stdint.h> #define kObjectFieldOffset sizeof(uintptr_t) struct swift_func_object { uintptr_t *original_type_ptr; #if defined(__x86_64__) uintptr_t *unknown0; #else uintptr_t *unknown0, *unknown1; #endif uintptr_t function_address; uintptr_t *self; }; uintptr_t _rd_get_func_impl(void *func) { struct swift_func_object *obj = (struct swift_func_object *)*(uintptr_t *)(func + kObjectFieldOffset); return obj->function_address; }
54. SWIFT RUNTIME
55. ▸ libswiftCore.dylib implementations of NSSwiftArray, etc. ▸ libswiftRuntime.a low-level primitives like swift_release
56. HOPPER
57. COMPATIBILITY ▸ App Compatibility ✅ ▸ Binary Compatibility ⛔️ ▸ Source Compatibility ⛔️
58. Foo.app boris$ find . -type f ./Frameworks/libswiftCore.dylib ./Frameworks/libswiftCoreGraphics.dylib ./Frameworks/libswiftCoreImage.dylib ./Frameworks/libswiftDarwin.dylib ./Frameworks/libswiftDispatch.dylib ./Frameworks/libswiftFoundation.dylib ./Frameworks/libswiftObjectiveC.dylib ./Frameworks/libswiftUIKit.dylib ./Info.plist ./PkgInfo ./Foo
59. TWO FINAL TIDBITS
60. SPEED ▸ less dynamic dispatch ▸ omits _cmd - freeing one register ▸ usually no pointer aliasing int *ptrA = malloc(100 * sizeof(*ptrA)); int *ptrB = ptrA;
61. class BankAccount { var balance: Double = 0.0 func deposit(amount: Double) { balance += amount } } let account = BankAccount() account.deposit(100) let depositor = BankAccount.deposit depositor(account)(100) BankAccount.deposit(account)(100)
62. METHODS ARE CURRIED FUNCTIONS
64. YOU DON'T NEED OBJECTIVE-C ANYMORE
65. UNLESS YOU BUILD FRAMEWORKS OR NEED TO WORK WITH C++
66. BUT THE OBJC RUNTIME IS STILL STRONG
67. THANK YOU!
68. ▸ https://www.mikeash.com/pyblog/ ▸ http://airspeedvelocity.net/ ▸ https://developer.apple.com/swift/blog/ ▸ http://www.russbishop.net/swift-how-did-i-do-horrible-things
69. @NeoNacho boris@contentful.com http://buegling.com/talks