为什么NSUserDefaults无法在iPhone SDK中保存NSMutableDictionary? [英] Why NSUserDefaults failed to save NSMutableDictionary in iPhone SDK?
问题描述
我想在 NSUserDefaults
中保存 NSMutableDictionary
对象。 NSMutableDictionary
中的键类型是 NSString
,值类型为 NSArray
,其中包含实现 NSCoding
的对象列表。每个文档, NSString
和 NSArray
都符合 NSCoding
。
我遇到这个错误:
[NSUserDefaults setObject:forKey: ]:尝试插入NSCFDictionary类的非属性值....
任何解决方案?
我发现了一个替代方法,在保存之前,我对根对象( NSArray
)使用 NSKeyedArchiver
以 NSData
结尾。然后使用UserDefaults保存 NSData
。
当我需要数据时,我读出 NSData
,并使用 NSKeyedUnarchiver
将 NSData
转换回对象。
这是一个有点麻烦,因为我需要转换/从 NSData
每次,但它只是工作。
每个请求都有一个示例:
保存:
NSUserDefaults * defaults = [NSUserDefaults standardUserDefaults];
NSMutableArray * arr = ...; // set value
NSData * data = [NSKeyedArchiver archivedDataWithRootObject:arr];
[defaults setObject:data forKey:@theKey];
[defaults synchronize];
载入:
code> NSUserDefaults * defaults = [NSUserDefaults standardUserDefaults];
NSData * data = [defaults objectForKey:@theKey];
NSArray * arr = [NSKeyedUnarchiver unarchiveObjectWithData:data];
数组中的元素实现
@interface注释项:NSObject< NSCoding> {
NSString * value;
}
然后在执行 CommentItem
提供两种方法:
- (void)encodeWithCoder:(NSCoder *)encoder
{
[encoder encodeObject:value forKey:@Value];
}
- (id)initWithCoder:(NSCoder *)decoder
{
self.value = [decoder decodeObjectForKey:@Value];
return self;
}
任何人都有更好的解决方案?
感谢大家。
I'd like to save an NSMutableDictionary
object in NSUserDefaults
. The key type in NSMutableDictionary
is NSString
, the value type is NSArray
, which contains a list of object which implements NSCoding
. Per document, NSString
and NSArray
both are conform to NSCoding
.
I am getting this error:
[NSUserDefaults setObject: forKey:]: Attempt to insert non-property value.... of class NSCFDictionary.
Any solution for this?
I found out one alternative, before save, I encode the root object (NSArray
object) using NSKeyedArchiver
, which ends with NSData
. Then use UserDefaults save the NSData
.
When I need the data, I read out the NSData
, and use NSKeyedUnarchiver
to convert NSData
back to the object.
It is a little cumbersome, because i need to convert to/from NSData
everytime, but it just works.
Here is one example per request:
Save:
NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
NSMutableArray *arr = ... ; // set value
NSData *data = [NSKeyedArchiver archivedDataWithRootObject:arr];
[defaults setObject:data forKey:@"theKey"];
[defaults synchronize];
Load:
NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
NSData *data = [defaults objectForKey:@"theKey"];
NSArray *arr = [NSKeyedUnarchiver unarchiveObjectWithData:data];
The element in the array implements
@interface CommentItem : NSObject<NSCoding> {
NSString *value;
}
Then in the implementation of CommentItem
, provides two methods:
-(void)encodeWithCoder:(NSCoder *)encoder
{
[encoder encodeObject:value forKey:@"Value"];
}
-(id)initWithCoder:(NSCoder *)decoder
{
self.value = [decoder decodeObjectForKey:@"Value"];
return self;
}
Anyone has better solution?
Thanks everyone.
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