![ACCESSOR
• Use Accessor Methods to Get or Set Property Values
• Accessor methods are synthesized automatically by the compiler
@property float heightInMeters;
@synthesize heightInMeters;
Getter method : heightInMeters
Setter method : setHeightInMeters
[person setHeightInMeters:1.9];
float height = [person heightInMeters];](https://image.slidesharecdn.com/propertyandmmwitharc-130305202851-phpapp02/75/Property-and-MM-with-ARC-in-Objective-C-5-2048.jpg)
Uploaded byYo Yo Chen
Property and MM with ARC in Objective-C
This document discusses property and memory management in Objective-C. It covers properties, including attributes like accessor, writability, and atomicity. It then discusses object ownership and memory management, comparing manual reference counting (MRC) to automatic reference counting (ARC). ARC provides automatic memory management of Objective-C objects and avoids issues like retain cycles seen in MRC. The document provides examples and references for further reading.
Property and MM with ARC in Objective-C
- 1. Property And MemoryManagement in Objective-C By Yoyo Chen
- 2. AGENDA • 1.Property • 2.Object ownership • 3.Memory Management
- 3. PROPERTY • Objective-C properties ; a way to encapsulate an object’s values Ref: http://rypress.com/tutorials/objective-c/properties.html
- 4. Property Attribute Attribute Usage Accessor Getter/Setter method Writablity readwrite, readonly Semantics Without ARC retain/assign/copy With ARC strong/weak/copy/unsafe_unretained Atomicity atomic / nonatomic; Default:atomic
- 5. ACCESSOR • Use AccessorMethods to Get or Set Property Values • Accessor methods are synthesized automatically by the compiler @property float heightInMeters; @synthesize heightInMeters; Getter method : heightInMeters Setter method : setHeightInMeters [person setHeightInMeters:1.9]; float height = [person heightInMeters];
- 6. DOT SYNTAX • A concise Alternative to Accessor Method Calls • float height = person.heightInMeters; • person.heightInMeters = 1.9;
- 7. Atomic v.s nonatomic(1) Atomic • Is default behavior • Use in multi-threaded code Non-Atomic • Make setter method faster than atomic • Not thread safe • May result in unexpected behavior, when two different process access the same variable at the same time Advice: I don’t think you will write multi-threaded code anytime soon. And when you do, I don’t think atomic setter methods are going to help. 1.Objective-C Programming: The Big Nerd Ranch Guide :page 220 2. http://stackoverflow.com/questions/588866/atomic-vs-nonatomic-properties
- 8. Atomic v.s nonatomic(2) Advice: I don’t think you will write multi-threaded code anytime soon. And when you do, I don’t think atomic setter methods are going to help. Objective-C Programming: The Big Nerd Ranch Guide :page 220
- 9. • Memory Management 1.MRC(manualreference counting) 2.ARC(automatic reference counting)
- 10.
- 11. MRC (Manual Reference Counting) https://developer.apple.com/library/mac/#documentation/Cocoa/Conceptual/MemoryMgmt/Articles/MemoryMg
- 12. Automatic Reference Counting(ARC) • A compiler feature that provides automatic memory management of Objective-C objects. • Rather than having to think about retain and release operations, ARC allows you to concentrate on the interesting code. • ARC is supported in Xcode 4.2 or later, Mac OS X 10.6 or later, and iOS 4.0 or later(partially support), .
- 13. Transitioning to AutomaticReference Counting (ARC) https://developer.apple.com/library/ios/#releasenotes/ObjectiveC/RN-TransitioningToARC/Introduction/Introdu
- 14. ARC (Automatic Referencing Counting) • Pointers keep objects alive • If fisrName is a strong pointer , firstName is the owner of @”Ray” object • weak pointer, not the owner Ref:http://www.raywenderlich.com/5677/beginning-arc-in-ios-5-part-1
- 15.
- 16. • Revise First Name
- 17. • Click update http://developer.apple.com/library/ios/#documentation/cocoa/conceptual/ProgrammingWithObjectiveC/Encaps
- 18. • Zeroing WeakReferences Only available in Mac OS X ≥ 10.7 and iOS ≥ 5 Ref:http://www.raywenderlich.com/5677/beginning-arc-in-ios-5-part-1
- 19. • Avoid RetainCycle Ref :http://ios.sodas.tw/ntumpp-2012f/files/Lecture-2-iOS-in-Developers-view.pdf
- 20. • Avoid RetainCycle Ref :http://ios.sodas.tw/ntumpp-2012f/files/Lecture-2-iOS-in-Developers-view.pdf
- 21.
- 22. ARC limitation • ARC does not automate malloc/free, management of the lifetime of Core Foundation objects, file descriptors, and so on, you still free such resources by writing a dealloc method. http://developer.apple.com/library/ios/#releasenotes/ObjectiveC/RN-TransitioningToARC/Introduction/Introduct
- 24. DEMO • Memory leak: retain cycle
- 25. Objective-C Programming: TheBig Nerd Ranch Guide :page 125
- 26. • Product Profiler -> http://developer.apple.com/library/ios/#documentation/DeveloperTools/Conceptual/InstrumentsUserGuide/Mem