Objective-C Runtime

Mobilization 3 talk about Objective-C runtime

Transcript

1. Objective-C Runtime Michał Tuszyński iOS/Android developer, Friskylabs twitter, github: @srgtuszy
2. ROADMAP 1. How does Objective-C work? 2. Categories and properties using runtime 3. JSON object mapping with runtime 4. Method swizzling
3. Dynamic and static languages
4. Terminology #import <Foundation/Foundation.h>! ! @interface MyAwesomeClass : NSObject {! ! }! ! @end!
5. Terminology Object typedef struct objc_object {! Class isa;! } *id;! typedef struct objc_class *Class;!
6. Terminology 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! }! Class
7. Terminology
8. Terminology NSArray *array = [[NSArray alloc] init]; Creating a new object
9. Terminology Creating a new object
10. Terminology Selector A C string that represents given method name at runtime. Generated by the compiler and automatically mapped at runtime typedef struct objc_selector ! *SEL;!
11. Terminology IMP A C function pointer typedef id (*IMP)(id, SEL, ...); !
12. Terminology Message
13. Terminology Message
14. Messaging [array addObject:obj]; receiver message argument
15. Messaging [array addObject:obj]; receiver message argument objc_msgSend(array, @selector(addObject:), obj)
16. Messaging [array addObject:obj]; receiver message argument Two secret arguments: SEL _cmd Class *self
17. Messaging 1. Check for nil or ignored objects 2. Check cache for IMP method pointer 3. If it’s not there, check class dispatch table and continue up until found 4. If nothing is found, fallback to message forwarding
18. Messaging Message forwarding
19. Messaging Message forwarding Sometimes it makes sense to respond to unhandled messages
20. Associated Objects Since OSX 10.6 runtime offers to associate objects with each other
21. Associated Objects Since OSX 10.6 runtime offers to associate objects with each other void objc_setAssociatedObject(id object, void *key, id value, objc_AssociationPolicy policy) id objc_getAssociatedObject(id object, void *key)
22. Associated Objects demo
23. Inspecting properties
24. Inspecting properties objc_property_t * class_copyPropertyList(Class cls, unsigned int *outCount) C-array of all declared properties in given class
25. Inspecting properties NSString *keyName = @( property_getName(property) ); Fetching a property name
26. Property lookup demo
27. Method swizzling
28. Method swizzling Runtime allows us to exchange method implementations dynamically
29. Method swizzling
30. Method swizzling demo
31. WRAP UP
32. THANK YOU! Michał Tuszyński iOS/Android Developer, Friskylabs twitter, github: @srgtuszy