Create a new NsmutableArray in ios - ios

Question

Hello I am newbie to ios and objective c. I am working on a demo. In that I am having a for loop for adding values to NSMutableArray. Now this array will be added to NSMutableDictionary. Now inside this for loop i am having an if condition for checking string. I am adding objects to the array in "if" part and want to create a new Array when condition fail. I have tried as below, but in my Dictionary only one array saved. Can anyone help me where i have made mistake?
NSMutableArray *listingCommonArr,sectionTitles,eventDate;
int j=0;
NSString *dt;
NSMutableArray *sectionArray = [[NSMutableArray alloc]init];
sectionTitles = [orderedSet array];
NSLog(#"===listing common array---%d",[listingCommonArr count]);
sectionData = [[NSMutableDictionary alloc]init];
for(int i =0;i<[listingCommonArr count];i++)
{
dt = [[listingCommonArr objectAtIndex:i] objectForKey:#"start_date"];
NSLog(#"====my date at place===%# & my date is====%#",[sectionTitles objectAtIndex:j],dt);
for (int i =0; i < [listingCommonArr count]; i++) {
dt = [[listingCommonArr objectAtIndex:i] objectForKey:#"start_date"];
if ([(NSString *)[sectionTitles objectAtIndex:j] isEqualToString:dt]) {
[sectionArray addObject:listingCommonArr[i]];
//sectionData = #{dt : sectionArray}; // <-- PAY ATTENTION ON THIS LINE, PLEASE
//[sectionData setValue:sectionArray forKey:dt];
sectionData = [#{dt : sectionArray} mutableCopy];
} else {
[sectionData setObject:#"New value" forKey:#"string"];
sectionArray = [[NSMutableArray alloc]init];
j++;
}
}
NSLog(#"====my section DAta is==%#",sectionData);
}
errorTrace
-[__NSDictionaryI setObject:forKey:]: unrecognized selector sent to instance 0x7fc6547832a0
2015-12-18 19:39:41.387 iPhoneExploreCayman[41719:13822557] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[__NSDictionaryI setObject:forKey:]: unrecognized selector sent to instance 0x7fc6547832a0'
*** First throw call stack:
(
0 CoreFoundation 0x000000010a551c65 __exceptionPreprocess + 165
1 libobjc.A.dylib 0x000000010a1e8bb7 objc_exception_throw + 45
2 CoreFoundation 0x000000010a5590ad -[NSObject(NSObject) doesNotRecognizeSelector:] + 205
3 CoreFoundation 0x000000010a4af13c ___forwarding___ + 988
4 CoreFoundation 0x000000010a4aecd8 _CF_forwarding_prep_0 + 120
5 iPhoneExploreCayman 0x000000010604a48c -[iPhoneECListingView GetEventListingData:] + 1884
6 iPhoneExploreCayman 0x000000010605644b -[iPhoneECListingView EventListStart] + 1323
7 iPhoneExploreCayman 0x0000000106055a98 -[iPhoneECListingView EventClicked:] + 2312
8 UIKit 0x0000000108832d62 -[UIApplication sendAction:to:from:forEvent:] + 75
9 UIKit 0x000000010894450a -[UIControl _sendActionsForEvents:withEvent:] + 467
10 UIKit 0x00000001089438d9 -[UIControl touchesEnded:withEvent:] + 522
11 UIKit 0x000000010887f958 -[UIWindow _sendTouchesForEvent:] + 735
12 UIKit 0x0000000108880282 -[UIWindow sendEvent:] + 682
13 UIKit 0x0000000108846541 -[UIApplication sendEvent:] + 246

Answer 1

I'm highly confused about what you actually want to do here, but... after your comments I have completely updated my answer removing the previous assumptions about what actually is supposed to happen.
it seems to me you want(ed) to group a series of words by the first letter. you have posted a list of animals as example, so I worked with those.
you defined the expected output:
NSDictionary *_expectedOutput = #{#"A" :#[#"Affrican cat", #"Assian cat", #"Alsesian fox"], #"B" : #[#"Bear", #"Black Swan", #"Buffalo"], #"C" : #[#"Camel", #"Cockatoo"], #"D" : #[#"Dog", #"Donkey"], #"E" : #[#"Emu"], #"R" : #[#"Rhinoceros"], #"S" : #[#"Seagull"], #"T" : #[#"Tasmania Devil"], #"W" : #[#"Whale", #"Whale Shark", #"Wombat"]};
as you can see my input array is just an unsorted list of random names of animals from your sample output:
NSArray *_input = #[#"Whale Shark", #"Tasmania Devil", #"Affrican cat", #"Bear", #"Seagull", #"Black Swan", #"Whale", #"Wombat", #"Camel", #"Rhinoceros", #"Cockatoo", #"Buffalo", #"Assian cat", #"Alsesian fox", #"Emu"];
I'm working with that input array and I am going to group them by their first letter and build up the output:
NSMutableDictionary *_output = [NSMutableDictionary dictionary];
[[_input sortedArrayUsingSelector:#selector(compare:)] enumerateObjectsUsingBlock:^(NSString * _Nonnull obj, NSUInteger idx, BOOL * _Nonnull stop) {
NSString *_firstLetter = (obj.length > 0 ? [obj substringToIndex:1] : nil);
if (_firstLetter) {
NSMutableArray *_list = [_output valueForKey:_firstLetter];
if (_list == nil) {
_list = [NSMutableArray arrayWithObject:obj];
[_output setValue:_list forKey:_firstLetter];
} else {
[_list addObject:obj];
}
}
}];
that is pretty much it, if you'd log the _output, you can see on the console that is identical to your _expectedOutput collection.

Answer 2

you have sectionData = #{dt : sectionArray}; outside of the if section.
So on each iteration you dictionary will be recreated.
As I think you need the Mutable dictionary for sectionData, and move that string under "else" section
1 initialize mutable dictionary somewhere before the loop:
sectionData = [NSMutableDictionary new];
2 adding current array to dictionary must be under "else" block, also as I understand, you should create new sectionArray:
else
{
[sectionData setObject: sectionArray forKey:dt];
sectionArray = [[NSMutableArray alloc]init];
}

Answer 3

Every time you call sectionData = #{dt : sectionArray}; or anything sectionData is set other values are remove from dictionary and only last pair stays.(you are initializing dictionary every time you call setObject: forKey:)
If you want to create mutable dictionary and add objects to it you should do:
NSMutableDictionary *d2 = [NSMutableDictionary new];//sectionData in your case
[d2 addEntriesFromDictionary:#{#"b":#"c"}];//new key value pair added to d2
[d2 addEntriesFromDictionary:#{#"c":#"d"}];//new key value pair added to d2
[d2 addEntriesFromDictionary:#{#"d":#"e"}];//new key value pair added to d2