无法更新使用NSUserDefauts值初始化的NSMutableDictionary

Question

我使用NSUserDefaults来保存NSMutableDictionary。但是，当我从NSUserDefaults中检索值时，我无法修改/更新要保存值的NSMutableDictionary的值。

需要一些建议如何做到这一点？

Answer 1

您总是从NSUserDefaults获得NSDictionary的非可变实例。为了使它们变得可变，你需要做这样的事情：

dict = [[NSUserDefaults standardUserDefaults] objectForKey:@"myKey"]; 
myMutableDict = [dict mutableCopy]; 
// Note that the retain count is +1, so you will need to 
// release or autorelease myMutableDict later on. 

Answer 2

你也可以保存为plist。

这是你如何写一个的plist：

NSArray * paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES); 
NSString * docDirectory = [paths objectAtIndex:0]; 
NSString * dataFilePath = [docDirectory stringByAppendingPathComponent:@"YourFile.dat"] 

NSMutableDictionary * newLocalPlist = [[NSMutableDictionary alloc] init]; 

// add your prefs here 

[newLocalPlist writeToFile:dataFilePath atomically:YES]; 
[newLocalPlist release]; 

这就是你如何从plist中写着：

NSArray * paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES); 
NSString * docDirectory = [paths objectAtIndex:0]; 
NSString * dataFilePath = [docDirectory stringByAppendingPathComponent:@"YourFile.dat"] 
NSMutableDictionary * lastLocalPlist = [[[NSMutableDictionary alloc] initWithContentsOfFile:dataFilePath] autorelease];