Not Null validation for JSON Response iPhone App - iphone

Question

Currently I am using the following method to validate the data for not being Null.
if ([[response objectForKey:#"field"] class] != [NSNull class])
NSString *temp = [response objectForKey:#"field"];
else
NSString *temp = #"";
Problem comes when the response Dictionary contains hundreds of attributes (and respective values). I need to add this kind of condition to each and every element for the dictionary.
Any other way around to accomplish?
Any Suggestion for making any change to the web service (except not inserting the null value to database)?
Any Idea, Anyone ??

Answer 1

What I've done is put a category on NSDictionary
#interface NSDictionary (CategoryName)
/**
* Returns the object for the given key, if it is in the dictionary, else nil.
* This is useful when using SBJSON, as that will return [NSNull null] if the value was 'null' in the parsed JSON.
* #param The key to use
* #return The object or, if the object was not set in the dictionary or was NSNull, nil
*/
- (id)objectOrNilForKey:(id)aKey;
#end
#implementation NSDictionary (CategoryName)
- (id)objectOrNilForKey:(id)aKey {
id object = [self objectForKey:aKey];
return [object isEqual:[NSNull null]] ? nil : object;
}
#end
Then you can just use
[response objectOrNilForKey:#"field"];
You can modify this to return a blank string if you'd like.

Answer 2

First a minor point: your test is not idiomatic, you should use
if (![[response objectForKey:#"field"] isEqual: [NSNull null]])
If you want all keys in your dictionary that have a value of [NSNull null] to be reset to the empty string, the easiest way to fix it is
for (id key in [response allKeysForObject: [NSNull null]])
{
[response setObject: #"" forKey: key];
}
The above assumes response is a mutable dictionary.
However, I think you really need to review your design. You shouldn't be allowing [NSNull null] values at all if they are not allowed in the database.

Answer 3

It's not quite clear for me what you need but:
If you need to check whether the value for key is not NULL you can do this:
for(NSString* key in dict) {
if( ![dict valueForKey: key] ) {
[dict setValue: #"" forKey: key];
}
}
If you have some set of required keys, you can create static array and then do this:
static NSArray* req_keys = [[NSArray alloc] initWithObjects: #"k1", #"k2", #"k3", #"k4", nil];
Then in the method where you check your data:
NSMutableSet* s = [NSMutableSet setWithArray: req_keys];
NSSet* s2 = [NSSet setWithArray: [d allKeys]];
[s minusSet: s2];
if( s.count ) {
NSString* err_str = #"Error. These fields are empty: ";
for(NSString* field in s) {
err_str = [err_str stringByAppendingFormat: #"%# ", field];
}
NSLog(#"%#", err_str);
}

Answer 4

static inline NSDictionary* DictionaryRemovingNulls(NSDictionary *aDictionary) {
NSMutableDictionary *returnValue = [[NSMutableDictionary alloc] initWithDictionary:aDictionary];
for (id key in [aDictionary allKeysForObject: [NSNull null]]) {
[returnValue setObject: #"" forKey: key];
}
return returnValue;
}
response = DictionaryRemovingNulls(response);