Pointer confusion
开发者_Python百科I am confused about one pointer situation explained below;
In class A
@property(nonatomic,retain)NSMutableArray *words;
In class B
@property(nonatomic,retain)NSMutableArray *words;
//creating a pointer to words from classB
self.words = [classB words];
Now if I add new word to words array in Class A, why don't I see that word in words array in class B? I thought my words array in Class B is a pointer to Class A words?
Basically the changes should reflect in both arrays, until you change the reference of any of the two objects some where in your code.
//creating a pointer to words from classB
self.words = [classB words];
And some where in your Class A or Class B,
self.words = someOtherArray;
This will make the words array of both the classes to point different objects.
is it the code you try to run ? If yes, it seems there is a mystake in your class B code since words in class B is the same as [classB words]. (in class B : self.words = [classB words]). Maybe an instruction like : self.words = [classA words].... should resolve your problem (assuming classA is an object of class A).
As some of you guys here said it should work and it is. I had some errors in my code. But wanted to give a little example code to prove that this is how it should be:
#import "PointersAppDelegate.h"
#import "PointersViewController.h"
#import "ClassA.h"
#import "ClassB.h"
@implementation PointersAppDelegate
@synthesize window=_window;
@synthesize viewController=_viewController;
@synthesize classA, classB;
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
classA = [[ClassA alloc] init];
classB = [[ClassB alloc] init];
self.window.rootViewController = self.viewController;
[self.window makeKeyAndVisible];
//Add new word to words in classA
[[classA words] addObject:@"two"];
//Print words in classB
[classB print];
return YES;
}
- (void)dealloc
{
[_window release];
[_viewController release];
[classA release];
[classB release];
[super dealloc];
}
@end
//Class A
// ClassA.h
@interface ClassA : NSObject {
NSMutableArray *words;
}
@property(nonatomic,retain)NSMutableArray *words;
@end
// ClassA.m
#import "ClassA.h"
@implementation ClassA
@synthesize words;
- (id)init{
self = [super init];
if (self) {
words = [[NSMutableArray alloc] initWithObjects:@"one", nil];
}
return self;
}
- (void)dealloc {
[words release];
[super dealloc];
}
@end
ClassB
// ClassB.h
#import <Foundation/Foundation.h>
@interface ClassB : NSObject {
NSMutableArray *words;
}
@property(nonatomic,retain)NSMutableArray *words;
-(void)print;
@end
// ClassB.m
#import "ClassB.h"
#import "PointersAppDelegate.h"
@implementation ClassB
@synthesize words;
- (id)init{
self = [super init];
if (self) {
self.words = [[(PointersAppDelegate*)[[UIApplication sharedApplication] delegate] classA] words];
}
return self;
}
-(void)print{
for(int i=0;i<[words count];i++)
NSLog(@"%@", [words objectAtIndex:i]);
}
- (void)dealloc {
[words release];
[super dealloc];
}
@end
The result is:
2011-07-04 12:38:33.759 Pointers[20059:707] one
2011-07-04 12:38:33.767 Pointers[20059:707] two
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