對象參考

Question

我有一種iPhone編程的情況。我有一個包含另一個對象（對象B）的對象（對象A）。有沒有辦法從對象B中引用對象A？如果是這樣，我該怎麼做？

Answer 1

你可以有類相互引用，就像這樣：

ClassA.h：

@class ClassB // let the compiler know that there is a class named "ClassB" 

@interface ClassA : NSObject { 
    ClassB *objectB; 
} 

@property (nonatomic, retain) ClassB *objectB; 

@end 

ClassB.h：

@class ClassA; // let the compiler know that there is a class named "ClassA" 

@interface ClassB : NSObject { 
    ClassA *objectA; 
} 

@property (nonatomic, assign) ClassA *objectA; // "child" object should not retain its "parent" 

@end 

ClassA.m：

#import "ClassA.h" 
#import "ClassB.h" 

@implementation ClassA 

@synthesize objectB; 

- (id)init { 
    if (self = [super init]) { 
     objectB = [[ClassB alloc] init]; 
     objectB.objectA = self; 
    } 

    return self; 
} 

@end 

ClassB.m：

#import "ClassA.h" 
#import "ClassB.h" 

@implementation ClassB; 

@synthesize objectA; 

- (id)init { 
    if (self = [super init]) { 
     // no need to set objectA here 
    } 

    return self; 
} 

@end 

Answer 2

號對象B都需要有自己的指針對象A