iOS How do I convert an NSData object to an NSDictionary object, and vice versa?

[moonman239]

Hello everyone,

In my Core Data model, I have an attribute that is of the NSData type. The data assigned to this attribute is supposed to represent a dictionary.

I can't use NSString's initWithData method. Nor can I use the JSON object serialization class.

 

[dotri84]

Why you can't use this ?

NSError* error;
NSDictionary* json = [NSJSONSerialization JSONObjectWithData:responseData
options:kNilOptions error:&error];

 

[moonman239]

Why you can't use this ?

NSError* error;
NSDictionary* json = [NSJSONSerialization JSONObjectWithData:responseData
options:kNilOptions error:&error];

Because I'm not dealing with JSON data.

 

[PBG4 Dude]

Quick internet search gives the following SO answer.

http://stackoverflow.com/questions/5513075/how-can-i-convert-nsdictionary-to-nsdata-and-vice-versa

The most popular answer does this using two lines of code.

 

[moonman239]

Why you can't use this ?

NSError* error;
NSDictionary* json = [NSJSONSerialization JSONObjectWithData:responseData
options:kNilOptions error:&error];

Just wanted to add that JSONObjectWithData's return value is supposed to be of type NSString.

Quick internet search gives the following SO answer.

http://stackoverflow.com/questions/5513075/how-can-i-convert-nsdictionary-to-nsdata-and-vice-versa

The most popular answer does this using two lines of code.

Thank you!

 

[chown33]

Just wanted to add that JSONObjectWithData's return value is supposed to be of type NSString.

No it's not. The returned typename is id:

+ (id)JSONObjectWithData:(NSData *)data options:(NSJSONReadingOptions)opt error:(NSError **)error

The description says "The top level object is an NSArray or NSDictionary."

 

[moonman239]

No it's not. The returned typename is id:

+ (id)JSONObjectWithData:(NSData *)data options:(NSJSONReadingOptions)opt error:(NSError **)error

The description says "The top level object is an NSArray or NSDictionary."

Oh, OK. I suppose the reason I got the warning is that I didn't get enough sleep last night.