iOS持久存储策略 [英] iOS persistent storage strategy

问题描述

我正在开发一个应用程序，将数据保存到本地文件系统。将被保存的数据将主要是NSString和NSDate。数据不会经常保存，也许新数据将在典型使用情况下输入10次。数据也应该是可检索的（CRUD）

I'm developing an app which will save data to the local file system. The data that will be saved will be mostly NSString and NSDate. The data will not be saved that often, perhaps new data will be entered 10 times at a typical usage. The data should also of course be retrievable (CRUD)

如何保存这些数据？首先是有必要建模这些对象吗？如果不是，我应该使用属性列表？或SQLLite3？

How should I save this data? First of all is it necessary to model these objects? If not should I use property lists? Or SQLLite3?

否则我应该归档类模型吗？使用SQLLite3？

Else should I archive the class models? Use SQLLite3?

编辑：我不小心遗漏了一些关于应用程序的重要信息。实际上，我的应用程序将有两个数据模型具有聚合关系。所以我的第一个数据模型（让我们称之为DataA）将有一个NSString和NSDate也将引用第二个数据模型（让我们称之为DataB），它本身将由一个NSString和一个NSArray组成。所以它现在有点复杂。如果来自DataB的对象被删除，它应该当然不再存在于DataA中（但是DataA的其余部分应该保持不变）。

I accidentally left out some vital information about the app. Actually my app will be having 2 data models which have an aggregated relationship. So my first data model (lets call it DataA) which will have a NSString and NSDate will also have a reference to the second data model (lets call it DataB) which itself will consist of a NSString and a NSArray. So it gets a little more complicated now. If an object from DataB gets deleted it should of course cease to exist in DataA (but the rest of DataA should be left untouched)

推荐答案

p>这种数据似乎非常简单的存储和检索，没有任何其他依赖项，如可怕的复杂对象图。

This kind of data seems to be very simple to store and retrieve and does not have any other dependencies such as a horridly complex object graph.

您应该存储此数据在平面文件或 NSUserDefaults 。

You should store this data in a flat file or in NSUserDefaults.

我将给你一个例子，使用对象归档使用 NSCoding 协议：

I'll give you an example of both, using object archiving with the use of the NSCoding protocol:

@interface ApplicationData <NSCopying, NSCoding> {}

@property (nonatomic, strong) NSDate *someDate;
@property (nonatomic, strong) NSDate *someOtherDate;

@property (nonatomic, copy) NSString *someString;
@property (nonatomic, copy) NSString *someOtherString;

@end

@implementation ApplicationData

@synthesize someDate = _someDate, someOtherDate = _someOtherDate, someString = _someString, someOtherString = _someOtherString;

- (NSArray *)keys {
   static dispatch_once_t once;
   static NSArray *keys = nil;
   dispatch_once(&once, ^{
      keys = [NSArray arrayWithObjects:@"someString", @"someOtherString", @"someDate", @"someOtherDate", nil];
  });
   return keys;
}

- (id) copyWithZone:(NSZone *) zone {
    ApplicationData *data = [[[self class] allocWithZone:zone] init];
    if(data) {
        data.someString = _someString;
        data.someOtherString = _someOtherString;     

        data.someDate = _someDate;
        data.someOtherDate = _someOtherDate;
        //...
    }
    return data;
 }

 - (void) encodeWithCoder:(NSCoder *) coder {
     [super encodeWithCoder:coder];

     NSDictionary *pairs = [self dictionaryWithValuesForKeys:[self keys]];

     for(NSString *key in keys) {
        [coder encodeObject:[pairs objectForKey:key] forKey:key];
     }
  }


  - (id) initWithCoder:(NSCoder *) decoder {
     self = [super initWithCoder:decoder];
     if(self) {
        for(NSString *key in [self keys]) {
           [self setValue:[decoder decodeObjectForKey:key] forKey:key];
        }
     }
     return self;
  }

  @end

委托，你可以这样做：

@interface AppDelegate (Persistence)

@property (nonatomic, strong) ApplicationData *data;

- (void)saveApplicationDataToFlatFile;
- (void)loadApplicationDataFromFlatFile;
- (void)saveApplicationDataToUserDefaults;
- (void)loadApplicationDataFromUserDefaults;

@end

@implementation AppDelegate (Persistence) 
@synthesize data;

- (NSString *)_dataFilePath {
   static NSString *path = nil;
   static dispatch_once_t once;
   dispatch_once(&once, ^{
     path = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) stringByAppendingPathComponent:@"xAppData.dat"];
   });
   return path;
}

- (void)loadApplicationDataFromUserDefaults {        
   NSData *archivedData = [[NSUserDefaults standardUserDefaults] objectForKey:@"appData"];
   self.data = [NSKeyedUnarchiver unarchiveObjectWithData:archivedData];
}

- (void)saveApplicationDataToUserDefaults {
   NSData *archivedData = [NSKeyedArchiver archivedDataWithRootObject:self.data];
   [[NSUserDefaults standardUserDefaults] setObject:archivedData forKey:@"appData"];
   [[NSUserDefaults standardUserDefaults] synchronize];
}

- (void)loadApplicationDataFromFlatFile {
   NSData *archivedData = [NSData dataWithContentsOfFile:[self _dataFilePath]];
   self.data = [NSKeyedUnarchiver unarchiveObjectWithData:archivedData];
}

- (void)saveApplicationDataToFlatFile {  
   NSData *archivedData = [NSKeyedArchiver archivedDataWithRootObject:self.data];
   [archivedData writeToFile:[self _dataFilePath] atomically:YES];
}

@end

免责声明：我尚未测试此代码。

Disclaimer: I have not tested this code.

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