Question

我有一个帮助类，旨在从Core Data获取数据并将其传递回视图控制器。这是代码：

查看控制器：

@interface AnnouncementsController : UIViewController

@property (nonatomic, retain) NSMutableArray *announcements;

@end

@implementation AnnouncementsController

@synthesize announcements;

- (void)viewDidLoad
{
    AnnouncementCoreDataHelper *announcementHelper = [[AnnouncementCoreDataHelper alloc] init];
    self.announcements = [announcementHelper selectAnnouncementsWithPredicate:@"isActive = 1" sortDescriptor:@"lastUpdated" sortAscending:NO];

    [super viewDidLoad];
}

@end

Core Data Helper 实施：

// Select one or more announcements based on a predicate if passed in and a sort order
- (NSMutableArray*)selectAnnouncementsWithPredicate:(NSString *)predicateString sortDescriptor:(NSString *)sortBy sortAscending:(BOOL)isAscending
{
    NSError *error = nil;

    // Build the entity and request
    NSEntityDescription *entity = [NSEntityDescription entityForName:@"Announcement" inManagedObjectContext:managedObjectContext];
    NSFetchRequest *request = [[NSFetchRequest alloc] init];
    [request setEntity:entity];

    if(predicateString)
    {
        // Set the search criteria
        NSPredicate *predicate = [NSPredicate predicateWithFormat:predicateString];
        [request setPredicate:predicate];
    }

    if(sortBy)
    {
        NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:sortBy ascending:isAscending];
        NSArray *sortDescriptors = [[NSArray alloc] initWithObjects:sortDescriptor, nil];
        [request setSortDescriptors:sortDescriptors];
    }

    // Perform the search
    NSMutableArray *results = [[managedObjectContext executeFetchRequest:request error:&error] mutableCopy];

    if(results == Nil)
    {
        NSLog(@"%@", error);
    }

    return results;    
}

问题是Core Data Helper在其NSMutableArray结果中返回两个对象，但View Controller的NSMutableArray公告为零。将NSMutableArray从帮助器传递回控制器后会有什么损失？如果我将所有变量和结果更改为NSArray，一切正常。

Answer 1

我相信这是Xcode的一个时髦问题。我清理并重新构建，一切正常。我为浪费你的时间而感到抱歉，感谢您的帮助！我想更多地了解内存管理问题。

iOS 5.0 - 将Helper类的NSMutableArray传递给View Controller

1 个答案: