Property vs. instance variable

by

Properties are just setters and getters for ivars and should (almost) always be used instead of direct access.

@interface APerson : NSObject {
    // NSString *_name;           //  necessary for legacy runtime
}

@property(readwrite) NSString *name;

@end

@implementation APerson
@synthesize name;                 // use name = _name for legacy runtime
@end

@synthesize creates in this case those two methods (not 100% accurate):

- (NSString *)name {
    return [[_name copy] autorelease];
}
- (void)setName:(NSString *)value {
    [value retain];
    [_name release];
    _name = value;
}

It’s easy now to distinguish between ivars and getters/setters. The accessors have got the self. prefix. You shouldn’t access the variables directly anyway.

Your sample code doesn’t work as it should be:

_myVar = some_other_object;      // _myVar is the ivar, not myVar.
self.myVar = some_other_object;  // works too, uses the accessors

More Related Contents:

  1. HTML character decoding in Objective-C / Cocoa Touch
  2. When do you make an underscore in front of an instance variable? [duplicate]
  3. Why do you use an underscore for an instance variable, but not its corresponding property? [duplicate]
  4. `[super viewDidLoad]` convention
  5. What are best practices that you use when writing Objective-C and Cocoa? [closed]
  6. Open Source Cocoa/Cocoa-Touch POP3/SMTP library?
  7. NSArray Equivalent of Map
  8. Best way to implement Enums with Core Data
  9. How to write a simple Ping method in Cocoa/Objective-C
  10. Obtaining an NSDecimalNumber from a locale specific string?
  11. NSString to NSArray
  12. Using MD5 hash on a string in cocoa? [duplicate]
  13. Multiple value enum in Obj-C
  14. Understanding reference counting with Cocoa and Objective-C
  15. How to write data in plist?
  16. Do you need to create an NSAutoreleasePool within a block in GCD?
  17. How do you implement global iPhone Exception Handling?
  18. How to check programmatically if an App is installed?
  19. Reading audio samples via AVAssetReader
  20. writing NSDictionary to plist in my app bundle
  21. NSOperation on the iPhone
  22. Enabling crash logs symbolication in Xcode 4.2
  23. What’s the best way to put a c-struct in an NSArray?
  24. Sorting NSString values as if NSInteger using NSSortDescriptor
  25. Bootstrap Server Error in Xcode IPHONE [duplicate]
  26. How do I auto size a UIScrollView to fit its content
  27. UITextField for Phone Number
  28. Why tack a protocol of NSObject to a protocol implementation
  29. Get video NSData from ALAsset url iOS
  30. Problem dealloc’ing memory used by UIImageViews with fairly large image in an UIScrollView

Leave a Comment