Let's say I have:
@interface Thing : NSObject
@property (nonatomic, ???) Thing *nextThing;
@property (nonatomic, ???) Thing *prevThing;
@end
and somewhere I keep a reference to the 'head' of this doubly-linked list. What
should ??? be, "retain", or "assign" in order to work properly? If I was using
ARC instead, would they be "strong" or "weak"? Assuming the list doesn't
contain circular references (i.e. a<->b<->c<->a) will releasing my 'head'
reference properly clean up if I have:
"doublist.h"
@class Thing;
@interface DoublyLinkedListClass
@property (nonatomic, retain) Thing *head;
@end
"doublist.m"
@implementation DoublyLinkedListClass
@synthesize head = _head;
…
-(void)dealloc
{
self.head = nil; // Is this begging for a problem?
[super dealloc];
}
…
@end
One way would be to walk the doubly-linked list and copy (the references)
into an NSMutableArray, and set the "nextThing" and "prevThing" instance
variables to nil as I go, then (with the list objects disconnected), release
the reference to the NSMutableArray. Is this overkill to avoid a leak? In this
case, the Thing objects are already in an NSMutableArray that's part of a
higher-level model; in fact, they're loaded into the array first, then I call a
private method of my DungeonModel class (the one that has the mutable array) to
"connect" the object references based on two NSInteger properties in Thing (not
shown above for clarity) that refer to the objects to be connected via the
index of their location in the mutable array.
A pity OS X wasn't in existence when I took all those Comp Sci. classes in
college, or maybe they might have had a course in "Data Structures using
Objective-C"… Ha! :)
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