Separate objects or strings in NSMutableArray? - ios

Question

I'm new with JSon stuff, so bear with me. I'm deserializing a JSon from a URL, and everything is fine until I try to separate the objects within. The app crashes and I get an error that I don't understand. Maybe you can help me see what I'm missing.
[NSURLConnection sendAsynchronousRequest:urlRequest queue:queue completionHandler:^(NSURLResponse *response, NSData *data, NSError *error){
if ([data length]>0 && error == nil) {
id jsonObject = [NSJSONSerialization JSONObjectWithData:data options:NSJSONReadingAllowFragments error:&error];
if (jsonObject != nil && error == nil) {
if ([jsonObject isKindOfClass:[NSDictionary class]]) {
NSDictionary *deserializedDictionary = [[NSDictionary alloc] init];
deserializedDictionary = jsonObject;
NSLog(#"Deserialized Dictionary = %#",deserializedDictionary);
/*
LOG: Deserialized Dictionary = { d = "[{\"unit\":\"P101\",\"price\":36.0000,\"stat\":\"process\",\"type\":\"P12\"},{\"unit\":\"P102\",\"price\":38.0000,\"stat\":\"process\",\"type\":\"P13\"},..}
*/
NSMutableArray *dicts = [[NSMutableArray alloc] init];
dicts = (NSMutableArray *)deserializedDictionary[#"d"];
NSLog(#"Print dicts: %#",dicts);
/*
LOG: Print dicts: [{"unit":"P101","price":36.0000,"stat":"process","type":"P12"},{"unit":"P102","price":38.0000,"stat":"process","type":"P13"},..]
*/
NSLog(#"%#",NSStringFromClass([dicts class]));
//LOG: __NSCFString
NSMutableDictionary *myDict = [[NSMutableDictionary alloc] init];
for (myDict in dicts)
{
NSLog(#"myDict objectForKey: id-> %# myDict objectForKey: result-> %#",[myDict objectForKey:#"unit"],[myDict objectForKey:#"result"]);
}
}
And then I get this error:
[__NSCFString countByEnumeratingWithState:objects:count:]: unrecognized selector sent to instance 0x7fe97b327790
2016-03-08 11:29:12.946 Poop[49680:5673839] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[__NSCFString countByEnumeratingWithState:objects:count:]: unrecognized selector sent to instance 0x7fe97b327790'
Help, please?

Answer 1

From your code and log i can understand that actual issue is on your server side as from these lines
NSMutableArray *dicts = [[NSMutableArray alloc] init];
dicts = (NSMutableArray *)deserializedDictionary[#"d"];
NSLog(#"Print dicts: %#",dicts);
/*
LOG: Print dicts: [{"unit":"P101","price":36.0000,"stat":"process","type":"P12"},{"unit":"P102","price":38.0000,"stat":"process","type":"P13"},..]
*/
NSLog(#"%#",NSStringFromClass([dicts class]));
//LOG: __NSCFString
Log says your variable named dicts is of type NSCFString not NSMutableArray and NSString don't have keys and Enumeration can not run on NSString type of object.
Issue is with your API response, which is not returning correct JSON.
Solution is to change on your server side to return array or dictionary instead of string.

Answer 2

See the edited code:
[NSURLConnection sendAsynchronousRequest:urlRequest queue:queue completionHandler:^(NSURLResponse *response, NSData *data, NSError *error){
if ([data length]>0 && error == nil) {
id jsonObject = [NSJSONSerialization JSONObjectWithData:data options:NSJSONReadingAllowFragments error:&error];
if (jsonObject != nil && error == nil) {
if ([jsonObject isKindOfClass:[NSDictionary class]]) {
NSDictionary *deserializedDictionary = [[NSDictionary alloc] init];
deserializedDictionary = jsonObject;
NSLog(#"Deserialized Dictionary = %#",deserializedDictionary);
/*
LOG: Deserialized Dictionary = { d = "[{\"unit\":\"P101\",\"price\":36.0000,\"stat\":\"process\",\"type\":\"P12\"},{\"unit\":\"P102\",\"price\":38.0000,\"stat\":\"process\",\"type\":\"P13\"},..}
*/
NSMutableArray *responseArray = [[NSMutableArray alloc] init];
responseArray = deserializedDictionary[#"d"];
NSLog(#"Print responseArray: %#",responseArray);
/*
LOG: Print dicts: [{"unit":"P101","price":36.0000,"stat":"process","type":"P12"},{"unit":"P102","price":38.0000,"stat":"process","type":"P13"},..]
*/
NSLog(#"%#",NSStringFromClass([responseArray class]));
//LOG: __NSCFString
//The correct way of fast enumeration.
for (NSMutableDictionary *myDict in dicts)
{
NSLog(#"myDict objectForKey: id-> %# myDict objectForKey: result-> %#",[myDict objectForKey:#"id"],[myDict objectForKey:#"result"]);
}
}
Also, you should always check the existence of the key in the dictionary for each time you fetch the value from the dictionary, for this you can add this method in your HelperClass,
//Check is key exist in the dictionary
+(BOOL)validateKeyValueForData:(id)dataValue {
if([dataValue isEqual:[NSNull null]] || dataValue == nil)
{
return NO;
}
if([dataValue isKindOfClass:[NSArray class]] || [dataValue isKindOfClass:[NSMutableArray class]])
{
if([dataValue isEqual:[NSNull null]] || dataValue == nil || [dataValue count] <= 0)
{
return NO;
}
}
else
if([dataValue isKindOfClass:[NSDictionary class]] || [dataValue isKindOfClass:[NSMutableDictionary class]])
{
if([dataValue isEqual:[NSNull null]] || dataValue == nil || [dataValue count] <= 0)
{
return NO;
}
}
else if ([dataValue isKindOfClass:[NSString class]] || [dataValue isKindOfClass:[NSMutableString class]])
{
if([dataValue isEqual:[NSNull null]] || dataValue == nil || [dataValue length] <= 0)
{
return NO;
}
}
return YES;
}
And use this as
for (NSMutableDictionary *myDict in dicts)
{
//This way you make sure that the value for the specified key is exist in the dictionary.
if ([HelperClass validateKeyValueForData:myDict[#"id"]] && [HelperClass validateKeyValueForData:myDict[#"result"]]) {
NSLog(#"myDict objectForKey: id-> %# myDict objectForKey: result-> %#",[myDict objectForKey:#"id"],[myDict objectForKey:#"result"]);
}
}

Answer 3

It looks like dicts object is somehow being instantiated as a string. Take a look at the raw NSData, before it is parsed into a JSON object:
NSString *rawResponse = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];
NSLog(#"Raw data: %#", rawResponse);
If you set a general breakpoint to catch all exceptions, it might stop where you are trying to iterate through your dicts array. You can do this by:
Select the Breakpoints Navigator
Click the '+' button in the lower left
Select 'Add Exception Breakpoint...'
In the popup options menu, select the Break 'On Catch' option