如何在iOS中保存数据 [英] How to save data in iOS

问题描述

我正在制作游戏，当我关闭应用程序时（关闭多任务管理器），我的所有数据都消失了！所以，我的问题很简单：如何保存数据？

解决方案

让我们说你想要保存分数和级别，这两个属性都是名为dataHolder的对象的属性。

DataHolder可以创建为单例，所以你不必太担心关于你从哪里访问它（实际上是 sharedInstance ）：

它的代码看起来有点像这样： / p>

DataHolder.h

  #import <基金会/ Foundation.h> 
 
 @interface DataHolder：NSObject 
 
 +（DataHolder *）sharedInstance; 
 
 @property（assign）int level; 
 @property（assign）int score; 
 
  - （void）saveData; 
  - （void）loadData; 
 
 @end 
  

DataHolder.m

  NSString * const kLevel = @kLevel; 
 NSString * const kScore = @kScore; 
 
 @implementation DataHolder 
 
  - （id）init 
 {
 self = [super init]; 
 if（self）
 {
 _level = 0; 
 _score = 0; 
} 
返回自我; 
} 
 
 +（DataHolder *）sharedInstance 
 {
静态MDataHolder * _sharedInstance = nil; 
 static dispatch_once_t onceSecurePredicate; 
 dispatch_once（& onceSecurePredicate，^ 
 {
 _sharedInstance = [[self alloc] init]; 
}）; 
 
返回_sharedInstance; 
} 
 
 //在这个例子中，你将数据保存到NSUserDefault的
 //你可以将它保存到一个文件或一些更复杂的
 //数据结构：取决于你需要什么，真的是
 
  - （void）saveData 
 {
 [[NSUserDefaults standardUserDefaults] 
 setObject：[NSNumber numberWithInt：self.score] forKey：kScore]; 
 
 [[NSUserDefaults standardUserDefaults] 
 setObject：[NSNumber numberWithInt：self.level] forKey：kLevel]; 
 
 [[NSUserDefaults standardUserDefaults] synchronize]; 
} 
 
  - （void）loadData 
 {
 if（[[NSUserDefaults standardUserDefaults] objectForKey：kScore]）
 {
 self。得分= [（NSNumber *）[[NSUserDefaults standardUserDefaults] 
 objectForKey：kScore] intValue]; 
 
 self.level = [（NSNumber *）[[NSUserDefaults standardUserDefaults] 
 objectForKey：kLevel] intValue]; 
} 
其他
 {
 self.level = 0; 
 self.score = 0; 
} 
} 
 
 @end 
  

Don不要忘记#importDataHolder.h你需要的地方，或者只是把它放在 ...- Prefix.pch 。

您可以在 appDelegate 方法中执行实际加载和保存：

   - （void）applicationDidEnterBackground：（UIApplication *）application 
 {
 [[DataHolder sharedInstance] saveData]; 
} 
 
  - （void）applicationWillEnterForeground：（UIApplication *）application 
 {
 [[DataHolder sharedInstance] loadData]; 
} 
  

您可以使用 [DataHolder sharedInstance] .score 和 [DataHolder sharedInstance] .level 。

对于一个简单的任务来说，这似乎有些过分，但它确实有助于保持整洁，它可以帮助您避免将所有数据保存在 appDelegate （这通常是快速的&肮脏的解决方案）。

I'm making a game and when I close the app (close at multitask manager), all my data is gone! So, My question is very simple: How do I save the data?

解决方案

Let's say you want to save score and level, which are both properties of an object called dataHolder.

DataHolder can be created as a singleton, so you don't have to worry too much about from where you access it (its sharedInstance actually):

It's code would look a bit like this:

DataHolder.h

#import <Foundation/Foundation.h>

@interface DataHolder : NSObject 

+ (DataHolder *)sharedInstance;

@property (assign) int level;
@property (assign) int score;

-(void) saveData;
-(void) loadData;

@end

DataHolder.m

NSString * const kLevel = @"kLevel";
NSString * const kScore = @"kScore";

@implementation DataHolder

- (id) init
{
    self = [super init];
    if (self)
    {
        _level = 0;
        _score = 0;
    }
    return self;
}

+ (DataHolder *)sharedInstance
{
    static MDataHolder *_sharedInstance = nil;
    static dispatch_once_t onceSecurePredicate;
    dispatch_once(&onceSecurePredicate,^
                  {
                      _sharedInstance = [[self alloc] init];
                  });

    return _sharedInstance;
}

//in this example you are saving data to NSUserDefault's
//you could save it also to a file or to some more complex
//data structure: depends on what you need, really

-(void)saveData
{
    [[NSUserDefaults standardUserDefaults] 
        setObject:[NSNumber numberWithInt:self.score] forKey:kScore];

    [[NSUserDefaults standardUserDefaults] 
        setObject:[NSNumber numberWithInt:self.level] forKey:kLevel];

    [[NSUserDefaults standardUserDefaults] synchronize];
}

-(void)loadData
{
    if ([[NSUserDefaults standardUserDefaults] objectForKey:kScore])
    {
        self.score = [(NSNumber *)[[NSUserDefaults standardUserDefaults] 
            objectForKey:kScore] intValue];

        self.level = [(NSNumber *)[[NSUserDefaults standardUserDefaults] 
            objectForKey:kLevel] intValue];
    }
    else
    {
        self.level = 0;
        self.score = 0;
    } 
}

@end

Don't forget to #import "DataHolder.h" where you need it, or simply put it in ...-Prefix.pch.

You could perform actual loading and saving in appDelegate methods:

- (void)applicationDidEnterBackground:(UIApplication *)application
{
    [[DataHolder sharedInstance] saveData];
}

- (void)applicationWillEnterForeground:(UIApplication *)application
{
    [[DataHolder sharedInstance] loadData];
}

You can access your score and level data from anywhere with [DataHolder sharedInstance].score and [DataHolder sharedInstance].level.

This might seem like an overkill for a simple task but it sure helps to keep things tidy and it can help you to avoid keeping all the data in appDelegate (which is usually the quick & dirty path to solution).

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