ios - 如何在 iOS 应用程序中保存数据？

Question

我正在开发一个应用程序，用户可以在其中创建一个包含 3 个字段的事件:

类别、名称、事件。在用户输入后，我有一个保存按钮，可以保存他的数据以供将来引用。然后，当他再次打开应用程序时，数据将显示在表格 View 中。

我如何在 iOS 上“保存”数据？我知道 NSUserDefaults ，但我很确定这不是这个例子的方式。

到目前为止我做了什么:

我用类别、名称、事件创建了一个“Note”类。

我的保存按钮的代码如下所示:

- (IBAction)save:(id)sender {

    //creating a new "note" object
    Note *newNote = [[Note alloc]init];

    newNote.category = categoryField.text;
    newNote.name = nameField.text;
    newNote.event = eventField.text;

    // do whatever you do to fill the object with data

    NSData* data = [NSKeyedArchiver archivedDataWithRootObject:newNote];

    /*
     Now we create the path to the documents directory for your app
     */

    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory,
                                                         NSUserDomainMask, YES);
    NSString *documentsDirectory = [paths objectAtIndex:0];

    /*
     Here we append a unique filename for this object, in this case, 'Note'
     */

    NSString* filePath = [documentsDirectory stringByAppendingString:@"Note"];

    /*
     Finally, let's write the data to our file
     */

    [data writeToFile:filePath atomically:YES];

    /*
     We're done!
     */
}

这是保存事件的正确方法吗？我现在如何检索我写的内容？

其次，如果我再次运行这段代码，我会覆盖数据，还是创建新条目？

我想看看如何每次都创建一个新条目。

另外，我想从我向他们展示的表中删除一个事件，所以我想看看删除是如何工作的。

我的“笔记”对象看起来像这样:

@interface Note : NSObject <NSCoding> {
    NSString *category;
    NSString *name;
    NSString *event;
}

@property (nonatomic, copy) NSString *category;

@property (nonatomic, copy) NSString *name;

@property (nonatomic, copy) NSString *event;

@end

Answer 1

尝试

//Note.h 

#define kNoteCategory  @"Category"
#define kNoteName      @"Name"
#define kNoteEvent     @"Event"

@interface Note : NSObject

@property (nonatomic, copy) NSString *category;
@property (nonatomic, copy) NSString *name;
@property (nonatomic, copy) NSString *event;

- (id)initWithDictionary:(NSDictionary *)dictionary;

+ (NSArray *)savedNotes;
- (void)save;

//Note.m文件

- (id)initWithDictionary:(NSDictionary *)dictionary
{
    self = [super init];
    if (self)
    {
        self.category = dictionary[kNoteCategory];
        self.name = dictionary[kNoteName];
        self.event = dictionary[kNoteEvent];
    }

    return self;
}

+ (NSString *)userNotesDocumentPath
{
    NSString *documentsPath  = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES)[0] stringByAppendingPathComponent:@"UserNotes.plist"];

    return documentsPath;

}

+ (NSArray *)savedNotes
{
    NSString *documentsPath = [self userNotesDocumentPath];
    NSArray *savedNotes = [NSArray arrayWithContentsOfFile:documentsPath];
    NSMutableArray *savedUserNotes = [@[] mutableCopy];
    for (NSDictionary *dict in savedNotes) {
        Note *note = [[Note alloc]initWithDictionary:dict];
        [savedUserNotes addObject:note];
    }

    return savedUserNotes;

}

- (NSDictionary *)userNoteDictionary
{
    NSMutableDictionary *dict = [NSMutableDictionary dictionary];

    if (self.category) {
        dict[kNoteCategory] = self.category;
    }
    if (self.name) {
        dict[kNoteName] = self.name;
    }
    if (self.event) {
        dict[kNoteEvent] = self.event;
    }

    return dict;
}

- (void)saveUserNotesToPlist:(NSArray *)userNotes
{
    NSMutableArray *mutableUserNotes = [@[] mutableCopy];
    for (Note *note in userNotes) {
        NSDictionary *dict = [note userNoteDictionary];
        [mutableUserNotes addObject:dict];
    }
    NSString *documentsPath  = [Note userNotesDocumentPath];
    [mutableUserNotes writeToFile:documentsPath atomically:YES];
}

#pragma mark - Save

- (void)save
{
    NSMutableArray *savedNotes = [[Note savedNotes] mutableCopy];
    [savedNotes addObject:self];
    [self saveUserNotesToPlist:savedNotes];
}

保存笔记

- (IBAction)save:(id)sender {

    //creating a new "note" object
    Note *newNote = [[Note alloc]init];

    newNote.category = categoryField.text;
    newNote.name = nameField.text;
    newNote.event = eventField.text;

    //Saves the note to plist
    [newNote save];

    //To get all saved notes
    NSArray *savedNotes = [Note savedNotes];
}

Source Code