为什么 plist 中的项目会被覆盖？

Question

我正在尝试向我的 plist 添加一个新项目。但是，每次我按保存时它都会被覆盖：

-(IBAction)save:(id)sender {

 appDelegate = (JobTestAppDelegate*)[[UIApplication sharedApplication]delegate]; 

 NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
 NSString *documentsDirectory = [paths objectAtIndex:0];
 NSString *fileName = [documentsDirectory stringByAppendingPathComponent:@"Work.plist"];

 NSMutableDictionary* newNote = [[NSMutableDictionary alloc] init];  

 NSMutableDictionary *set = [NSMutableDictionary dictionaryWithObjects:[NSArray arrayWithObjects:@"", @"", nil] forKeys:[NSArray arrayWithObjects:@"Work Name", @"Work ID", nil]];

NSArray *work = [NSArray arrayWithObjects:set, nil];

int row = 0;
newNote = [appDelegate.job objectAtIndex:row];
[newNote setValue:work forKey:@"Work"];         

[appDelegate.job writeToFile:fileName atomically:TRUE];

[newNote release];  

[self dismissModalViewControllerAnimated:YES];
 }

我不知道代码的哪一部分是错误的。这几天我一直在努力解决这个问题。

编辑： appDelegate.job - 我的主应用程序委托类中的一个可变数组，用于创建 plist：

    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *documentsDirectory = [paths objectAtIndex:0];
NSString *fileName = [documentsDirectory stringByAppendingPathComponent:@"Work.plist"];

job = [[NSMutableArray alloc] initWithContentsOfFile:fileName];


[job writeToFile:fileName atomically:YES];

EDIT2：

我需要将用户输入（NSArray*work）存储到工作数组中

根（数组）

        Item 0 (Dict)
                      Name (String)
                      Work (Array)
                                       Item 0 (Dict)
                                                    Work Name (String)
                                                    Work ID (String)
                                       Item 1 (Dict)
                                                    Work Name (String)
                                                    Work ID (String)
        Item 1 (Dict)
                      Name (String)
                      Analysis (Array)
                                       Item 0 (Dict)
                                                    Work Name (String)
                                                    Work ID (String)
                                       Item 1 (Dict)
                                                    Work Name (String)
                                                    Work ID (String)

编辑3： NSMutableDictionary* newNote = [[NSMutableDictionary alloc] init];

 NSMutableDictionary *set = [NSMutableDictionary dictionaryWithObjects:[NSArray arrayWithObjects:@"", @"", nil] forKeys:[NSArray arrayWithObjects:@"Work Name", @"Work ID", nil]];

NSArray *work = [NSArray arrayWithObjects:set, nil];

int row = item;
newNote = [appDelegate.job objectAtIndex:row];
[newNote setValue:work forKey:@"Work"];         

//i think this is the line which i am having problem with.
//without this line my data in the plist gets overwritten, 
//with this code it copies the who item and create a new item into my root array
[appDelegate.job addObject:newNote];

[appDelegate.job writeToFile:fileName atomically:TRUE];

[newNote release];  

提前致谢， 莉安娜

Answer 1

您正在用新项目覆盖作业索引为零的任何内容。您也在此处分配内存：

NSMutableDictionary* newNote = [[NSMutableDictionary alloc] init]; 

然后在这里给这个变量重新赋值：

newNote = [appDelegate.job objectAtIndex:row];

如果您尝试添加新项目，您应该执行以下操作：

NSMutableDictionary* newNote = [[NSMutableDictionary alloc] init];
[newNote setValue:work forKey:@"Work"];
[appDelegate.job addObject:newNote];
[appDelegate.job writeToFile:fileName atomically:TRUE];

然后，您将向作业数组添加一个新字典，并写出整个数组。

编辑：从您的 cmets 看来，newNote 应该是一个字典，其中包含一个名称和一个数组。因此，您需要向现有数组添加一个新对象 - 您当前正在将单个项目数组设置为该字典的“工作”键。

你需要这样的东西：

NSMutableDictionary* newNote = [appDelegate.job objectAtIndex:0];
NSArray *oldWork = [newNote objectForKey:@"Work"];
NSArray *newWork = [oldWork arrayByAddingObject:set];
[newNote setObject:newWork forKey:@"Work"];