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iOS Build a Simple iPhone App with Objective-C Creating a Data Model Creating a Data Collection

self & .

sometime we add "self" keyword to call and sometimes we add"_", why its so.

ViewController.h
#import "UIViewController.h"

@interface ViewController : UIViewController

@property (strong, nonatomic) NSString *shoppingCart;
@property (strong, nonatomic) NSArray *shoppingList;

@end
ViewController.m
#import "ViewController.h"

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];

    // Add your code below!
    self.shoppingList = @[@"toothpaste",@"bread",@"eggs"];
}

@end

3 Answers

Patrick Cooney
Patrick Cooney
12,216 Points

When you use self. you're calling the pre-built setter. It's the same as if you created a method like the following

-(void) setShoppingList:(NSArray *)list {
      _shoppingList = list;
}

using self. is the safe way to do it because you're using the setter rather than directly changing the ivar value in memory. Basically under the hood Xcode is setting the ivar value for you though.

can you please elaborate a little more with a better example. Help is much appreciated Thanks

Patrick Cooney
Patrick Cooney
12,216 Points

The best way I can describe it is _variable is accessing the value directly in the memory and self.variable is using the setter method. Maybe this post will help a bit more? (It's long but it might be just what you need).