好的，我花了最近两天的时间试图对这个进行排序。我有一个控制我的属性列表的类，它被用作单例类，所以它只被实例化一次，并且它有一个其他方法用于将值保存到plist。
无论你做什么，plist工作都很好，直到你从多任务栏中删除应用程序（即完全关闭应用程序）然后plist中的所有值都被重置为null ..但是plist不会丢失。
所以我现在想的是，我可能会覆盖我在plist中的值，这些值是我在根文档目录中为读写功能所做的。我希望我的代码示例你们可能能够发现我的错误...我不确定我还需要添加什么......如果你有任何问题可以帮助我帮助我回答这个问题那么请让我知道。
任何帮助都将受到极大的赞赏，我的孩子的孩子将在你的首次亮相。
#import "EnginePropertiesController.h"
static EnginePropertiesController *sharedMyManager = nil;
@implementation EnginePropertiesController
@synthesize pSignature;
@synthesize pVersion;
@synthesize rNumber;
@synthesize dVReturned;
@synthesize cacheValue;
@synthesize manu;
@synthesize mod;
@synthesize submod;
#pragma mark Singleton Methods
+ (id)sharedManager {
@synchronized(self) {
if (sharedMyManager == nil)
sharedMyManager = [[self alloc] init];
}
return sharedMyManager;
}
- (id)init {
if (self = [super init]) {
// 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"];
NSLog(@"myplist path read = %@", plistPath);
// 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];
manu = [cacheValue objectForKey:@"Manu"];
mod = [cacheValue objectForKey:@"Mod"];
submod = [cacheValue objectForKey:@"SubMod"];
if (tempRoot && [tempRoot count]){
// assign values
self.pVersion = [tempRoot objectForKey:@"PSignature"];
self.pVersion = [tempRoot objectForKey:@"PVersion"];
self.rNumber = [tempRoot objectForKey:@"RNumber"];
self.dVReturned = [tempRoot objectForKey:@"DVReturned"];
cacheValue = [tempRoot objectForKey:@"Cache Value"];
}
}
return self;
}
- (void) saveData:(NSString *)methodName pSignature:(NSString *)TemppSignature pVersion:(NSNumber *)TemppVersion rNumber:(NSNumber *)TemprNumber dVReturned:(NSNumber *)TempdvReturned 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.pSignature = TemppSignature;
self.pVersion = TemppVersion;
self.rNumber = TemprNumber;
self.dVReturned = TempdVReturned;
//This checks with methodName I would like to save the value from
//The reason for this is there are 3 different cache values I get at seperate times to save This if statment just makes sure they are in the correct order.
if ([methodName isEqualToString:@"Getmanu"]) {
self.manu = cValue;
} else if ([methodName isEqualToString:@"GetMod"]) {
self.mod = cValue;
} else if ([methodName isEqualToString:@"GetSubMod"]) {
self.submod = cValue;
}
//Set up cacheValue Dictionary that will be added to the property list root dictionary
self.cacheValue = [NSDictionary dictionaryWithObjectsAndKeys:
manu, @"Manu",
mod, @"Mod",
subMod, @"SubMod", nil];
//Pass appropriate values into plist
NSDictionary *plistDict = [NSDictionary dictionaryWithObjectsAndKeys:
protocolSignature, @"Protocol Signature",
pVersion, @"Protocol Version",
rNumber, @"Request Number",
dVReturned, @"Data Version returned",
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];
} else {
NSLog(@"Error in saveData: %@", error);
}
}
@end
答案 0 :(得分：2)
这是一个问题：pVersion被分配两次，而pSignature仍然是nil。
self.pVersion = [tempRoot objectForKey:@"PSignature"];
self.pVersion = [tempRoot objectForKey:@"PVersion"];
这应该是
self.pSignature = [tempRoot objectForKey:@"PSignature"];
self.pVersion = [tempRoot objectForKey:@"PVersion"];
这反过来会导致节省时间的麻烦：
NSDictionary *plistDict = [NSDictionary dictionaryWithObjectsAndKeys:
pSignature, @"PSignature",
pVersion, @"PVersion",
rNumber, @"RNumber",
dVReturned, @"DVReturned",
cacheValue, @"Cache Value", nil];
这个构造函数不知道它有多少个参数，只是一直持续到nil。如果pSignature为零，则会保存一个空字典。
虽然立即解决方案是修复pSignature读数，但使用dictionaryWithObjectsAndKeys:构建字典总是很脆弱。使用setObject:forKey单独存储每个对象要好得多。如果对象为nil，则抛出异常，因此在调用之前进行测试。
NSMutableDictionary *plistDict = [NSMutableDictionary dictionary];
if (pSignature) [plistDict setObject:pSignature forKey:@"PSignature"];
if (pVersion) [plistDict setObject:pVersion forKey:@"PVersion"];
// ... and so on.
存储的另一个选择是序列化。请参阅Archives and Serializations Programming Guide。这需要权衡：虽然保存和加载在工作时更简单，但生成的文件不易被人类阅读。
最后，有三个地方放置日志语句，断点或对话框，这有助于这样的情况：
arrayWithObjects:和dictionaryWithObjectsAndKeys: