我正在使用KVC序列化NSObject
并尝试将其保存到NSUserDefaults
,这在我尝试存储NSDictionary
时会给我一个Attempt to insert non-property value
。
以下是所讨论对象MyClass
:的属性
@interface MyClass : NSObject
@property (copy,nonatomic) NSNumber* value1;
@property (copy,nonatomic) NSNumber* value2;
@property (copy,nonatomic) NSString* value3;
@property (copy,nonatomic) NSString* value4;
@property (copy,nonatomic) NSString* value5;
@property (copy,nonatomic) NSString* value6;
@property (copy,nonatomic) NSString* value7;
@property (copy,nonatomic) NSString* value8;
@end
到了保存MyClass的时候,它发生在这里:
-(void)saveMyClass
{
NSArray* keys = [NSArray arrayWithObjects:
@"value1",
@"value2",
@"value3",
@"value4",
@"value5",
@"value6",
@"value7",
@"value8",
nil];
NSDictionary* dict = [self dictionaryWithValuesForKeys:keys];
for( id key in [dict allKeys] )
{
NSLog(@"%@ %@",[key class],[[dict objectForKey:key] class]);
}
NSUserDefaults* defaults = [NSUserDefaults standardUserDefaults];
[defaults setObject:dict forKey:[NSString stringWithString:kMyClassKey]];
[defaults synchronize];
}
它产生这个输出:
2012-02-23 19:35:27.518 MyApp[10230:40b] __NSCFConstantString __NSCFNumber
2012-02-23 19:35:27.519 MyApp[10230:40b] __NSCFConstantString __NSCFNumber
2012-02-23 19:35:27.519 MyApp[10230:40b] __NSCFConstantString __NSCFString
2012-02-23 19:35:27.519 MyApp[10230:40b] __NSCFConstantString __NSCFString
2012-02-23 19:35:27.520 MyApp[10230:40b] __NSCFConstantString __NSCFString
2012-02-23 19:35:27.520 MyApp[10230:40b] __NSCFConstantString __NSCFString
2012-02-23 19:35:27.520 MyApp[10230:40b] __NSCFConstantString __NSCFString
2012-02-23 19:35:27.520 MyApp[10230:40b] __NSCFConstantString NSNull
2012-02-23 18:38:48.489 MyApp[9709:40b] *** -[NSUserDefaults setObject:forKey:]: Attempt to insert non-property value '{
value1 = "http://www.google.com";
value2 = "MyClassData";
value3 = 8;
value4 = "<null>";
value5 = "http://www.google.com";
value6 = 1;
value7 = "http://www.google.com";
value8 = 4SY8KcTSGeKuKs7s;
}' of class '__NSCFDictionary'. Note that dictionaries and arrays in property lists must also contain only property values.`
如您所见,dict
中的所有对象都是属性列表值,其所有键都是NSString*
。为了执行这项任务,我缺少什么琐事?或者我应该放弃并使用writeToFile
或类似产品?
建议Kevin打印值,当然其中一个值的类型是NSNull
,它不是属性列表值。谢谢
我的问题的笨拙解决方案——迭代我刚刚用dictionaryWithValuesForKeys
方便地生成的字典的键,并删除NSNull
类型的键。叹息
NSMutableDictionary* dict = [NSMutableDictionary dictionaryWithDictionary:[self dictionaryWithValuesForKeys:keys]];
for( id key in [dict allKeys] )
{
if( [[dict valueForKey:key] isKindOfClass:[NSNull class]] )
{
// doesn't work - values that are entered will never be removed from NSUserDefaults
//[dict removeObjectForKey:key];
[dict setObject@"" forKey:key];
}
}
在将字典保存为用户默认值时,我通常会对其进行归档和取消归档。这样就不必手动检查NSNull
值。
只需将以下两个方法添加到代码中即可。可能属于某一类别。
- (BOOL)archive:(NSDictionary *)dict withKey:(NSString *)key {
NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
NSData *data = nil;
if (dict) {
data = [NSKeyedArchiver archivedDataWithRootObject:dict];
}
[defaults setObject:data forKey:key];
return [defaults synchronize];
}
- (NSDictionary *)unarchiveForKey:(NSString *)key {
NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
NSData *data = [defaults objectForKey:key];
NSDictionary *userDict = nil;
if (data) {
userDict = [NSKeyedUnarchiver unarchiveObjectWithData:data];
}
return userDict;
}
然后,您可以像这样归档任何字典(假设该方法在类中可用):
NSDictionary *dict = ...;
[self archive:dict withKey:@"a key of your choice"];
然后再像这样检索:
NSDictionary *dict = [self unarchiveForKey:@"a key of your choice"];
如果你需要储存;
- 来自自定义对象的数据
- 或自定义对象的数组
您可以使用NSKeyedArchiver方法。你可以用这个方法查利维坦的答案。
但是,如果您正在尝试存储;
- 包含NSString或NSNumber的字典(类似于从JSON服务响应转换的字典)
- 或这种字典的数组
您不需要使用NSKeyedArchiver。您可以使用用户默认值。
在我的例子中,当我从用户默认值检索字典时,它返回的是nil,所以我认为NSUserDefaults不愿意保存我的字典。
然而,它被保存了,但我使用了错误的getter方法从用户默认值中检索它;
[[NSUserDefaults standardUserDefaults] stringForKey:<my_key>]
请确保您使用了其中之一;
[[NSUserDefaults standardUserDefaults] dictionaryForKey:<my_key>]
或;
[[NSUserDefaults standardUserDefaults] objectForKey:<my_key>]
在检查任何其他可能的原因之前。