ios-save nsdictionary in nsuserdefault - ios

Question

i want to save a nsdictionary have value null in nsuserdefault and don't need replace and delete value null
How?
My code -> impossible save in nsuserdefault
NSMutableArray * _itemsNames;
NSString * itemsFilename;
- (void) responseArray:(NSMutableArray *)array {
[_itemsNames setArray:array];
[spinner stopAnimating];
[_itemsNames writeToFile:itemsFilename atomically:YES];
NSMutableSet *filepathsSet = [[NSUserDefaults standardUserDefaults] objectForKey:#"test"];
[filepathsSet setByAddingObject:itemsFilename];
[[NSUserDefaults standardUserDefaults] setObject:filepathsSet forKey:#"test"];
}
The json is:(have value null)
({
ID:11,
name:21-12-2012,
des:"<null>",
url:
[
{
ID:1,
name: "<null>"
},
{
ID:2,
name:"<null>"
}
]
},
{
ID:12,
name:if i die young,
des:"<null>",
url:
[
{
ID:3,
name: "<null>"
},
{
ID:21,
name:"<null>"
}
]
})

Answer 1

If you have dictionary myDict
Then
[[NSUserDefaults standardUserDefaults] setObject:myDict forKey:#"MyDictionary"];
myDict will be saved only if it contains all objects that implements NSCoding
Regarding your null concept.
There is no need to save nil values in dictionary for a key.
If you try to get an object for a key and in dictionary there isn't any object related to that key then it will return nil. So no need to save null values

Answer 2

If you really need to store null values in NSDictionary use NSNull. Anyway you can just not store key with null value and then for [mydict objectForKey:#"keyWithNullValue"] you'll get nil.
But as I said if you really really want to store null use something like that:
NSSet *mySet = [NSSet setWithObjects:#{
#"ID":#(11),
#"name":#"21-12-2012",
#"des":[NSNull null],
#"url": #[#{
#"ID":#(1),
#"name": [NSNull null]
}, #{
#"ID":#(2),
#"name":[NSNull null]
}]
},#{
#"ID":#(12),
#"name":#"if i die young",
#"des":[NSNull null],
#"url": #[#{
#"ID":#(3),
#"name": [NSNull null]
}, #{
#"ID":#(21),
#"name":[NSNull null]
}]}, nil];

Answer 3

You mention saving dictionaries, but all you are showing is the JSON representation of an array of dictionaries.
You don't need to do anything strange, take the returned JSON data and turn it into an array and write the array to a plist. Turning it into a string and then trying to make a collection out of it is probably causing you the problems.