3

我正在尝试将.plist我创建的数据保存到我NSUserDefaults的数据中，以便我可以保存我放入其中的数据，因此如果应用程序停止（从多任务栏中删除），我不会丢失这些值。

我在这里被指出了本教程

其中有这个示例代码。

-(void)saveToUserDefaults:(NSString*)myString
{
    NSUserDefaults *standardUserDefaults = [NSUserDefaults standardUserDefaults];

    if (standardUserDefaults) {
        [standardUserDefaults setObject:myString forKey:@"Prefs"];
        [standardUserDefaults synchronize];
    }
}

-(NSString*)retrieveFromUserDefaults
{
    NSUserDefaults *standardUserDefaults = [NSUserDefaults standardUserDefaults];
    NSString *val = nil;

    if (standardUserDefaults) 
        val = [standardUserDefaults objectForKey:@"Prefs"];

    return val;
}

我想要一些帮助的是，以上内容与储蓄有何关系.plists？

我有一个.plist控制器类，它读取捆绑包在根文档中.plist创建一个新.plist的，然后读取并写入它......所以当应用程序退出或关闭时我如何使用上面的来保存它？

这就是我加载和写入我.plist的，目前使用单例并且它在自己的类中的方式。

#pragma mark Singleton Methods
+ (id)sharedManager {
    @synchronized(self) {
        if (sharedMyManager == nil)
            sharedMyManager = [[self alloc] init];
    }
    return sharedMyManager;
}
- (id)init {
    if (self = [super init]) {

        // Data.plist code
        // get paths from root direcory
        NSArray *paths = NSSearchPathForDirectoriesInDomains (NSDocumentDirectory, NSUserDomainMask, YES);
        // get documents path
        NSString *documentsPath = [paths objectAtIndex:0];
        // get the path to our Data/plist file
        NSString *plistPath = [documentsPath stringByAppendingPathComponent:@"EngineProperties.plist"];

        // check to see if Data.plist exists in documents
        if (![[NSFileManager defaultManager] fileExistsAtPath:plistPath])
        {
            // if not in documents, get property list from main bundle
            plistPath = [[NSBundle mainBundle] pathForResource:@"EngineProperties" ofType:@"plist"];
        }

        // read property list into memory as an NSData object
        NSData *plistXML = [[NSFileManager defaultManager] contentsAtPath:plistPath];
        NSString *errorDesc = nil;
        NSPropertyListFormat format;
        // convert static property liost into dictionary object
        NSDictionary *tempRoot = (NSMutableDictionary *)[NSPropertyListSerialization propertyListFromData:plistXML mutabilityOption:NSPropertyListMutableContainersAndLeaves format:&format errorDescription:&errorDesc];
        if (!tempRoot)
        {
            NSLog(@"Error reading plist: %@, format: %d", errorDesc, format);
        }
        // assign values
        self.signature = [tempRoot objectForKey:@"Signature"];
        self.version = [tempRoot objectForKey:@"Version"];
        self.request = [tempRoot objectForKey:@"Request"];
        self.dataVersion = [tempRoot objectForKey:@"Data Version"];

        man = [cacheValue objectForKey:@"Man"];
        mod = [cacheValue objectForKey:@"Mod"];
        sub = [cacheValue objectForKey:@"SubMod"];

        cacheValue = [tempRoot objectForKey:@"Cache Value"];
    }


    - (void) saveData:(NSString *)methodName signature:(NSString *)pSignature Version:(NSNumber *)pVersion request:(NSNumber *)rNumber dataVersion:(NSNumber *)dvReturned cacheValue:(NSNumber *)cValue;
    {
        // get paths from root direcory
        NSArray *paths = NSSearchPathForDirectoriesInDomains (NSDocumentDirectory, NSUserDomainMask, YES);
        // get documents path
        NSString *documentsPath = [paths objectAtIndex:0];
        // get the path to our Data/plist file
        NSString *plistPath = [documentsPath stringByAppendingPathComponent:@"EngineProperties.plist"];

        // set the variables to the values in the text fields
        self.signature = pSignature;
        self.version = pVersion;
        self.request = rNumber;
        self.dataVersion = dvReturned;

        //do some if statment stuff here to put the cache in the right place or what have you.
        if (methodName == @"manufacturers")
        {
            self.man = cValue; 
        }
        else if (methodName == @"models")
        {
            self.mod = cValue;
        }
        else if (methodName == @"subMod")
        {
            self.sub = cValue;
        }

        self.cacheValue = [NSDictionary dictionaryWithObjectsAndKeys:
                           man, @"Manufacturers",
                           mod, @"Models",
                           sub, @"SubModels", nil];


        NSDictionary *plistDict = [NSDictionary dictionaryWithObjectsAndKeys:
                                   signature, @"Signature",
                                   version, @"Version",
                                   request, @"Request",
                                   dataVersion, @"Data Version",
                                   cacheValue, @"Cache Value", nil];



        NSString *error = nil;
        // create NSData from dictionary
        NSData *plistData = [NSPropertyListSerialization dataFromPropertyList:plistDict format:NSPropertyListXMLFormat_v1_0 errorDescription:&error];

        // check is plistData exists
        if(plistData)
        {
            // write plistData to our Data.plist file
            [plistData writeToFile:plistPath atomically:YES];

            NSString *myString = [[NSString alloc] initWithData:plistData encoding:NSUTF8StringEncoding];
            //        NSLog(@"%@", myString);
        }
        else
        {
            NSLog(@"Error in saveData: %@", error);
            //        [error release];
        }
    }


    @end
4

2 回答 2

6

你不能写 a .plistinto NSUserDefaults，至少实际上不能。要实现这一点，您必须从其中写入特定的密钥，.plist这NSUserDefaults基本上就像保存所有数据的两个副本。您可以将其NSUserDefaults视为.plist可以读取和写入的不可见文件，而实际上无法看到文件。使用NSUserDefaults，即使应用程序在多任务处理中被杀死，您也可以恢复保存的值。

但是，您如何选择.plist以及NSUserDefaults应该基于您需要保存多少数据。Apple 建议仅将少量数据保存到NSUserDefaults. 如果您需要保存大量信息，那么.plist就是要走的路。要么，要么当然Core-Data。

于 2012-04-11T01:47:42.303 回答
0

.plist 是一个键值对文件。这本质上是一本字典。当您将数据存储在 .plist 中时，您就是在持久化它。即使您的应用程序被杀死，您也可以取回它。

NSUserDefaults 也是如此。它更干净，更快捷。因此，任何一种方法都足够了。

于 2012-04-11T01:38:31.203 回答