除NSDictionary外，所有可从其他类访问的类属性?任何人都知道为什么

Question

在过去的几天里，我到处找，除了几根头发外，几乎没有什么可看的。

我正试图通过@properties将我的对象数据从一个类传递到另一个类，所有这些都能很好地处理我的NSString对象。但我无法访问我的NSDictionary（和/或NSMutableDictionary）数据。事实上，我已经尝试过将我的NSDictionary切换到NSMutableDictionary，在保留和复制之间切换，以及其他一些变体，但都无济于事。

以下是明细。我正在传递的NSDictionary对象是projectMessagesList。我希望这是足够简短的代码，但提供足够的信息：

DBSProject.h

@interface DBSProject : NSObject <NSCoding>
@property (nonatomic, retain) NSDictionary *projectMessagesList;
@end

DBSProject.m

@implementation DBSProject
@synthesize projectMessagesList=_projectMessagesList;
-(id)init {
    self = [super init];
    if (self) {
        [self setProjectCode:@"CODE"];
        NSMutableDictionary *projectMessagesList = [[NSMutableDictionary alloc] init];
        DBSMessage *message = [[DBSMessage alloc] init];
        [message setMessageDate:[NSDate date]];
        [message setMessageText:[NSString stringWithFormat:@"This is a message"]];
        [projectMessagesList setObject:message forKey:@"msg"];
        NSLog(@"%@", [projectMessagesList objectForKey:@"msg"]);
        }
    }
    return self;
}

对象类末尾的NSLog在控制台中正确地打印出"这是一条消息"。

现在让我们跳到我的另一个类，一个ViewController:

DBSDetailViewController.h

#import "DBSProject.h"
#import "DBSMessage.h"
@interface DBSDetailViewController : UIViewController
@property (strong, nonatomic) DBSProject *myProject;
@property (strong, nonatomic) IBOutlet UILabel *clientCode;
@end

DBSDetailViewController.m

- (void)viewWillAppear:(BOOL)animated
{
    [super viewWillAppear:animated];
    NSString *clientProjectString = [NSString stringWithFormat:@"%@ %@", self.myProject.clientCode, self.myProject.projectCode];
    self.title = self.myProject.projectCode;
    self.projectCode.text = clientProjectString;
    self.projectDescription.text = self.myProject.projectDescription;
    self.projectBudget.text = self.myProject.projectBudget;
    self.projectDueDate.text = self.myProject.projectDueDate;
    DBSMessage *tmpMessage = [[DBSMessage alloc] init];
    tmpMessage = [self.myProject.projectMessagesList objectForKey:@"msg"];
    NSLog(@"%@", self.myProject.projectCode);
    NSLog(@"%@", [tmpMessage messageText]);
}

这正确地打印出了我的projectCode，但projectMessagesList（我的NSDictionary）是一个（null）。

因此，我可以访问除NSDictionary之外的所有内容。有人对我的错误有什么建议吗？非常感谢！

Answer 1

更改代码，这是一个非常简单的错误

-(id)init {
    self = [super init];
    if (self) {
        [self setProjectCode:@"CODE"];
        //you are not assigning the object into ivar..you are creating a local object
        //NSMutableDictionary *projectMessagesList = [[NSMutableDictionary alloc] init];
        //into
        projectMessagesList = [[NSMutableDictionary alloc] init];
        DBSMessage *message = [[DBSMessage alloc] init];
        [message setMessageDate:[NSDate date]];
        [message setMessageText:[NSString stringWithFormat:@"This is a message"]];
        [projectMessagesList setObject:message forKey:@"msg"];
        NSLog(@"%@", [projectMessagesList objectForKey:@"msg"]);
        }
    }
    return self;
}