Dynamic Swift
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The document discusses a Swift program that deals with dynamic method resolution and swizzling within the Objective-C runtime environment. It outlines class hierarchy involving an 'operation' class and attempts to execute a series of chained operations. The execution fails due to an error indicating that the 'thirdhandlertype' object does not have a member function 'dosomething'.
![Playground execution failed: error: Dynamic Swift.playground:35:1: error:
value of type 'ThirdHandlerType' has no member 'doSomething'
third.doSomething()
^~~~~ ~~~~~~~~~~~
* thread #1: tid = 0x61b09, 0x000000010f3713c0 Dynamic
Swift`executePlayground, queue = 'com.apple.main-thread', stop reason =
breakpoint 1.2
* frame #0: 0x000000010f3713c0 Dynamic Swift`executePlayground
frame #1: 0x000000010f3709c0 Dynamic Swift`__37-[XCPAppDelegate
enqueueRunLoopBlock]_block_invoke + 32
frame #2: 0x000000010fe8c6ac
CoreFoundation`__CFRUNLOOP_IS_CALLING_OUT_TO_A_BLOCK__ + 12
frame #3: 0x000000010fe716f4 CoreFoundation`__CFRunLoopDoBlocks + 356
frame #4: 0x000000010fe70e65 CoreFoundation`__CFRunLoopRun + 901
frame #5: 0x000000010fe70884 CoreFoundation`CFRunLoopRunSpecific + 420
frame #6: 0x000000011539ba6f GraphicsServices`GSEventRunModal + 161
frame #7: 0x0000000111b07c68 UIKit`UIApplicationMain + 159
frame #8: 0x000000010f3706e9 Dynamic Swift`main + 201
frame #9: 0x00000001134e568d libdyld.dylib`start + 1
frame #10: 0x00000001134e568d libdyld.dylib`start + 1
FAIL](https://image.slidesharecdn.com/dynamicswiftlightningtalk-170225052035/85/Dynamic-Swift-12-320.jpg)
Dynamic Swift
- 3. Objective C Runtime -(BOOL) resolveInstanceMethod:(SEL)aSelector -(id) forwardingTargetForSelector:(SEL)aSelector -(NSMethodSignature *) methodSignatureForSelector:(SEL)aSelector -(void) forwardInvocation:(NSInvocation *)anInvocation
- 8. "I want something that works like the responder chain…"
- 9. let first = FirstHandlerType() let second = SecondHandlerType(next: first) let third = ThirdHandlerType(next: second)
- 10. class Operation: NSObject { let nextOperation: Operation? init(next: Operation? = nil) { self.nextOperation = next } override func forwardingTarget(for aSelector: Selector!) -> Any? { print(String(describing: self)) return nextOperation } }
- 12. Playground execution failed: error: Dynamic Swift.playground:35:1: error: value of type 'ThirdHandlerType' has no member 'doSomething' third.doSomething() ^~~~~ ~~~~~~~~~~~ * thread #1: tid = 0x61b09, 0x000000010f3713c0 Dynamic Swift`executePlayground, queue = 'com.apple.main-thread', stop reason = breakpoint 1.2 * frame #0: 0x000000010f3713c0 Dynamic Swift`executePlayground frame #1: 0x000000010f3709c0 Dynamic Swift`__37-[XCPAppDelegate enqueueRunLoopBlock]_block_invoke + 32 frame #2: 0x000000010fe8c6ac CoreFoundation`__CFRUNLOOP_IS_CALLING_OUT_TO_A_BLOCK__ + 12 frame #3: 0x000000010fe716f4 CoreFoundation`__CFRunLoopDoBlocks + 356 frame #4: 0x000000010fe70e65 CoreFoundation`__CFRunLoopRun + 901 frame #5: 0x000000010fe70884 CoreFoundation`CFRunLoopRunSpecific + 420 frame #6: 0x000000011539ba6f GraphicsServices`GSEventRunModal + 161 frame #7: 0x0000000111b07c68 UIKit`UIApplicationMain + 159 frame #8: 0x000000010f3706e9 Dynamic Swift`main + 201 frame #9: 0x00000001134e568d libdyld.dylib`start + 1 frame #10: 0x00000001134e568d libdyld.dylib`start + 1 FAIL
- 14. let third: AnyObject = ThirdHandlerType(next: second)