释放对象的问题

Question

我有3级层次结构的导航应用程序。我的第一级是tabel视图控制器。该控制器的nib文件是“TableView”。我这里有问题。我的代码是这样的：

RootViewController的

#import "RootViewController.h"
#import "SubCategory.h"
#import "OffersViewController.h"

@implementation RootViewController

@synthesize subCategories;
@synthesize offersView;

- (void)dealloc
{
    NSLog(@"root dealloc");
    //[subCategories release];
    [super dealloc];
}

- (void)viewDidLoad
{
    NSLog(@"root view load");
    [super viewDidLoad];
    self.title  = @"Sub Categories";

    NSString *jsonArray = [NSString stringWithFormat:@"{ "
                       @" \"sub-categories\": { "
                       @" \"parent\": \"1\", "
                       @" \"count\": \"2\", "
                       @" \"sub-category\": [{ "
                       @" \"id\": \"1\", "
                       @" \"name\": \"Buy\" "
                       @" }, "
                       @" { "
                       @" \"id\": \"2\", "
                       @" \"name\": \"Sell\" "
                       @" }] "
                       @" } "
                       @" }"];

    SubCategory* categories = [[SubCategory alloc] init];
    subCategories = categories;
    [subCategories parseJSON:jsonArray];
}


- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView 
{
    NSLog(@"root sections");
return 1;
}


- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section 
{
    NSLog(@"root numberOfRows");
return [subCategories.subCategoryName count];
}


- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath 
{
    NSLog(@"root didSelectRow");
    OffersViewController * offers = [[OffersViewController alloc]    initWithNibName:@"OffersView" bundle:nil];

    offersView = offers;
    // I have exception on this row. exception is:
    //-[__NSArrayI objectAtIndex:]: message sent to deallocated instance 0x4b04c00
    offersView.title = [NSString stringWithFormat:@"%@", [subCategories.subCategoryName objectAtIndex:indexPath.row]];

    [self.navigationController pushViewController:offersView animated:YES];

}

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath 
{
    NSLog(@"root cellForRow");
    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:@"cachedCell"];
    if (cell == nil) {
        cell = [[[UITableViewCell alloc] init] autorelease];
    }

    cell.textLabel.text = [subCategories.subCategoryName objectAtIndex:indexPath.row];
    cell.accessoryType = UITableViewCellAccessoryDisclosureIndicator;

return cell;
}

@end

子类别

#import "SubCategory.h"
#import "JSON.h"

@implementation SubCategory

@synthesize parentId;
@synthesize count;
@synthesize subCategoryId;
@synthesize subCategoryName;


- (void) parseJSON: (NSString*) jsonArray {
     NSDictionary *results = [jsonArray JSONValue];

    NSString *parent = (NSString*) [[results objectForKey:@"sub-categories"] objectForKey:@"parent"];
    parentId = [parent intValue];

    NSString *cnt = (NSString*) [[results objectForKey:@"sub-categories"] objectForKey:@"count"];
    self.count = [cnt intValue];

    NSDictionary *subCategories = [[results objectForKey:@"sub-categories"] objectForKey:@"sub-category"];


    NSMutableArray *namesArray = [[NSMutableArray alloc] initWithCapacity:[subCategories count]];
    NSMutableArray* idArray = [[NSMutableArray alloc] initWithCapacity:[subCategories count]];

    for (NSDictionary *subCategory in subCategories) {        
        [idArray addObject:[subCategory objectForKey:@"id"]];
        [namesArray addObject:[subCategory objectForKey:@"name"]];
    }

    subCategoryId = [NSArray arrayWithArray:idArray];
    subCategoryName = [NSArray arrayWithArray:namesArray];

    [idArray release];
    [namesArray release];
//[parent release];
//[cnt release];
}

@end

我不知道为什么我的对象被释放了。有人可以帮助我。

编辑：添加了子类别代码

Answer 1

问题在于：

NSMutableArray *namesArray = [[NSMutableArray alloc] initWithCapacity:[subCategories count]];
NSMutableArray* idArray = [[NSMutableArray alloc] initWithCapacity:[subCategories count]];

...

subCategoryId = [NSArray arrayWithArray:idArray];
subCategoryName = [NSArray arrayWithArray:namesArray];

[idArray release];
[namesArray release];

此时，subCategoryId和subCategoryName已自动释放。这意味着在parseJSON:方法完成后将无法访问它们。您有两种选择：

// Because idArray and namesArray are already retained (you alloc'd them)
subCategoryId = idArray;
subCategoryName = namesArray;

或：

...
// this is equivalent to what you have now, except these two will be retained.
// this is different from the above because subCategoryId and subCategoryName are now NSArrays, whereas above they were NSMutableArrays.
subCategoryId = [idArray copy];
subCategoryName = [namesArray copy];
...

Answer 2

SubCategory类别的范围仅为viewDidLoad。如果您制作浅色副本，它/或副本将无法在您的范围之外使用，您需要在将其分配给子类别时保留它，例如

subCategories = [categories retain];

此外，您可以放弃使用SubCategory类别。而是做：

subCategories =  [[SubCategory alloc] init];     
[subCategories parseJSON:jsonArray]; }