We have an app that calls a SOAP web service and retrieves a long list of XML, which the app then parses into an NSArray of NSDictionary objects. The NSArray contains a list of Rental Apartment information, each of which is stored into an NSDictionary.
The entire list may contain 10 different types of Apartments (i.e. 2-room, 3-room), and we need to split the NSArray into smaller NSArrays based on Room-Type, which has the key "roomType" in the NSDictionary objects.
Currently our algorithm is
Use [NSArray valueForKeyPath:#"#distinctUnionofObjects.room-type"]
to obtain a list of unique room-type values.
Loop through the list of unique room-type values
For each unique room-type value, use NSPredicate to retrieve matching items from the Original list
Our code is below (renamed for clarity):
NSArray *arrOriginal = ... ...; // Contains the Parsed XML list
NSMutableArray *marrApartmentsByRoomType = [NSMutableArray arrayWithCapacity:10];
NSMutableArray *arrRoomTypes = [arrOriginal valueForKeyPath:#"distinctUnionOfObjects.roomType"];
for(NSString *strRoomType in arrRoomTypes) {
NSPredicate *predicateRoomType = [NSPredicate predicateWithFormat:#"roomType=%#", strRoomType];
NSArray *arrApartmentsThatMatchRoomType = [arrOriginal filteredArrayUsingPredicate:predicateRoomType]; // TAKES A LONG TIME EACH LOOP-ROUND
[marrApartmentsByRoomType addObject:arrApartmentsThatMatchRoomType];
}
However, step 3 is taking a long time as the original list may contain large amount (>100,000) of items. It seems that NSPredicate goes through the entire list for each key value. Is there a more efficient way of splitting a large NSArray into smaller NSArrays, based on NSDictionary keys?
If the order of your splited Arrays is not important, i have a solution for you:
NSArray *arrOriginal;
NSMutableDictionary *grouped = [[NSMutableDictionary alloc] initWithCapacity:arrOriginal.count];
for (NSDictionary *dict in arrOriginal) {
id key = [dict valueForKey:#"roomType"];
NSMutableArray *tmp = [grouped objectForKey:key];
if (tmp == nil) {
tmp = [[NSMutableArray alloc] init];
[grouped setObject:tmp forKey:key];
}
[tmp addObject:dict];
}
NSMutableArray *marrApartmentsByRoomType = [grouped allValues];
This is quite performant
- (NSDictionary *)groupObjectsInArray:(NSArray *)array byKey:(id <NSCopying> (^)(id item))keyForItemBlock
{
NSMutableDictionary *groupedItems = [NSMutableDictionary new];
for (id item in array) {
id <NSCopying> key = keyForItemBlock(item);
NSParameterAssert(key);
NSMutableArray *arrayForKey = groupedItems[key];
if (arrayForKey == nil) {
arrayForKey = [NSMutableArray new];
groupedItems[key] = arrayForKey;
}
[arrayForKey addObject:item];
}
return groupedItems;
}
Improving #Jonathan answer
Converting array to dictionary
Maintaining the same order as it was in original array
//only to a take unique keys. (key order should be maintained)
NSMutableArray *aMutableArray = [[NSMutableArray alloc]init];
NSMutableDictionary *dictFromArray = [NSMutableDictionary dictionary];
for (NSDictionary *eachDict in arrOriginal) {
//Collecting all unique key in order of initial array
NSString *eachKey = [eachDict objectForKey:#"roomType"];
if (![aMutableArray containsObject:eachKey]) {
[aMutableArray addObject:eachKey];
}
NSMutableArray *tmp = [grouped objectForKey:key];
tmp = [dictFromArray objectForKey:eachKey];
if (!tmp) {
tmp = [NSMutableArray array];
[dictFromArray setObject:tmp forKey:eachKey];
}
[tmp addObject:eachDict];
}
//NSLog(#"dictFromArray %#",dictFromArray);
//NSLog(#"Unique Keys :: %#",aMutableArray);
//Converting from dictionary to array again...
self.finalArray = [[NSMutableArray alloc]init];
for (NSString *uniqueKey in aMutableArray) {
NSDictionary *aUniqueKeyDict = #{#"groupKey":uniqueKey,#"featureValues":[dictFromArray objectForKey:uniqueKey]};
[self.finalArray addObject:aUniqueKeyDict];
}
Hope, It will help when client wants final array in same order as input array.
Related
This question already has answers here:
sort NSDictionary values by key alphabetical order
(4 answers)
Closed 6 years ago.
I have a dictionary in which, for a single key(for example key "0") there are a key value pair data.The keys are like name, id,p_id. I want to sort the NSMutableDictionary for the values related to the Key "name". The data in the dictionary is as follows,
0 = {
id = 12;
name = "Accounts ";
"p_id" = 13222071;
};
1 = {
id = 13;
name = "consultant";
"p_id" = 15121211;
};
2 = {
id = 11;
name = "Tania";
"p_id" = 10215921;
};
}
Any help is appreciated!
Please try out the below code:
[yourMutableArray sortUsingComparator: (NSComparator)^(NSDictionary *a, NSDictionary *b) {
NSString *key1 = [a objectForKey: #"name"];
NSString *key2 = [b objectForKey: #"name"];
return [key1 compare: key2];
}];
NSLog(#"Sorted Array By name key : %#", yourMutableArray);
Hope this helps!
NSArray *sortedKeys = [dict.allKeys sortedArrayUsingComparator:^NSComparisonResult(NSDictionary *d1, NSDictionary *d2) {
return [d1[#"name"] compare:d2[#"name"]];
}];
NSArray *objects = [dict objectsForKeys:sortedKeys notFoundMarker:[NSNull null]];
Dictionaries are not sorted, and doesn't resemble any order. What you should do is to getAll the keys first. Then apply a sort method on the keys, then request the objects according to the ordered keys.
E.g:
NSArray *keys = [dictionary allKeys];
NSArray *sortedKeys = <sort the keys according to your preferred method>
Now you can iterate the Dictionary from the order of the array sortedKeys.
While it has been made abundantly clear that Dictionaries can't be sorted and rightfully so, that does not mean the ends you are aiming for can't be achieved. This code will do that for you:
NSArray *arrayOfDicts = dic.allValues; //Now we got all the values. Each value itself is a dictionary so what we get here is an array of dictionaries
NSSortDescriptor *nameDescriptor = [[NSSortDescriptor alloc] initWithKey:#"name" ascending:YES]; //Create sort descriptor for key name
NSArray *sortingDesc = [NSArray arrayWithObject:nameDescriptor];
NSArray *sortedArray = [arrayOfDicts sortedArrayUsingDescriptors:sortingDesc]; //Get sorted array based on name
NSMutableDictionary *kindaSortedDict = [[NSMutableDictionary alloc] init];
int keyForDict=0;
for(NSDictionary *valDict in sortedArray)
{
[kindaSortedDict setObject:valDict forKey:[NSString stringWithFormat:#"%i",keyForDict]]; //Set values to our new dic which will be kind of sorted as the keys will be assigned to right objects
keyForDict++;
}
//Now you can simply get sorted array of keys from kindaSortedDic and results for them will always be sorted alphabetically. Alternatively you can just skip all that bother and directly use sortedArray
I have added comments in code to help you understand that.
For accessing sorted values I'd do this:
NSArray *sortedKeys = [kindaSortedDict.allKeys sortedArrayUsingDescriptors:
#[[NSSortDescriptor sortDescriptorWithKey:#"intValue"
ascending:YES]]];
for(NSString *key in sortedKeys)
{
NSDictionary *valDict = [kindaSortedDict objectForKey: key];
NSLog(#"Dict is: %# for key: %#",valDict,key);
}
I have an array which contains multiple Dictionaries each one with 3 keys (#"date", #"username", #"text").
What I want to check for, is whether the same user (#"username") exists in more than one dictionary in that Array. And, if she does, combine the text for those "duplicates" into one dictionary.
I have considered this answer to check for duplicates and this one
but I cannot figure out how to combine these two.
Jumping in here because although I think you should work on the code yourself first, I think Miro's answer is more complicated than the issue requires and though I like the idea of using predicates in Greg's answer, here's a 3rd solution that (1) wouldn't require you to change your data structure and (2) references the necessary loops...
The way I'd do it: Create an NSMutableArray then start adding the usernames in order. If the NSMutableArray already contains the username though, don't add another instance of the username, but instead merge the dictionary info.
ex.
// Note: I'm calling your array of user dictionaries userArray.
// Create a username array to store the usernames and check for duplicates
NSMutableArray *usernames = [[NSMutableArray alloc] init];
// Create a new userArray to store the updated dictionary info, merged
// entries et. al.
NSMutableArray *newUserArray = [[NSMutableArray alloc] init];
// Go through the array of user dictionaries
for (NSDictionary *userDict in userArray) {
// If the usernames array doesn't already contain the username,
// add it to both the usernames array and the newUserArray as is
if (![usernames containsObject:[userDict objectForKey:#"username"]]) {
[usernames addObject:[userDict objectForKey:#"username"]];
[newUserArray addObject:userDict];
}
// Otherwise, merge the userArray entries
else {
// Get a mutable copy of the dictionary entry at the first instance
// with this username
int indexOfFirstInstance = [usernames indexOfObject:[userDict objectForKey:#"username"]];
NSMutableDictionary *entry = [[newUserArray objectAtIndex:indexOfFirstInstance] mutableCopy];
// Then combine the "text" or whatever other values you wanted to combine
// by replacing the "text" value with the combined text.
// (I've done so with a comma, but you could also store the value in an array)
[entry setValue:[[entry objectForKey:#"text"] stringByAppendingString:[NSString stringWithFormat:#", %#", [userDict objectForKey:#"text"]]] forKey:#"text"];
// Then replace this newly merged dictionary with the one at the
// first instance
[newUserArray replaceObjectAtIndex:indexOfFirstInstance withObject:entry];
}
}
Maybe something like this [untested] example? Loop through, maintain a hash of existing items, and if a duplicate is found then combine with existing and remove.
NSMutableArray main; // this should exist, with content
NSMutableDictionary *hash = [[NSMutableDictionary alloc] init];
// loop through, backwards, as we're attempting to modify array in place (risky)
for(int i = [main count] - 1; i >= 0; i--){
// check for existing
if(hash[main[i][#"username"]] != nil){
int existingIdx = [hash[main[i][#"username"]] integerValue]; // get existing location
main[existingIdx][#"text"] = [main[existingIdx][#"text"] stringByAppendingString:main[i][#"text"]]; // "combine text" .. or however you'd like to
[main removeObjectAtIndex:i]; // remove duplicate
} else {
[hash setValue:[[NSNumber alloc] initWithInt:i] forKey:main[i][#"username"]]; // mark existance, with location
}
}
If you use NSMutableDictionary, NSMutableArray and NSMutableString you can do it with predicate like that:
NSMutableDictionary *d1 = [#{#"username": #"Greg", #"text" : [#"text 1" mutableCopy]} mutableCopy];
NSMutableDictionary *d2 = [#{#"username": #"Greg", #"text" : [#"text 2" mutableCopy]} mutableCopy];
NSMutableDictionary *d3 = [#{#"username": #"John", #"text" : [#"text 3" mutableCopy]} mutableCopy];
NSMutableArray *array = [#[d1, d2, d3] mutableCopy];
NSPredicate *predicate = [NSPredicate predicateWithFormat:#"username = %#", #"Greg"];
NSArray *filterArray = [array filteredArrayUsingPredicate:predicate];
NSMutableDictionary * firstDict = filterArray[0];
for (NSDictionary *d in filterArray)
{
if (firstDict != d)
{
[firstDict[#"text"] appendString:d[#"text"]];
[array removeObject:d];
}
}
i have 2 nsarrays
1 with nsdictionary's another with nsnumbers
NSArray *arr1 = #[#{#"id":#1},#{#"id":#2},#{#"id":#3},#{#"id":#4}];
NSArray *arr2 = #[#3,#1,#4,#2];
and i want to sort my arr1 through their id following the order of arr2
is this possible?
The problem with using sortedArrayUsingComparator: is you start dealing with O(n^2) lookup times. For each sort comparison in the first array, you have to do a lookup in the second array.
Your best bet is to take advantage of a hash table to reduce that to O(n) average complexity.
Your first step is to create a dictionary using id as a key. The result would look something like #{#1: #{#"id":#"1"}, ...}. Then you just have to construct an array by looping through arr3 and grabbing the values.
NSArray *arr1 = #[#{#"id":#1},#{#"id":#2},#{#"id":#3},#{#"id":#4}];
NSArray *arr2 = #[#3,#1,#4,#2];
NSMutableDictionary *map = [NSMutableDictionary dictionary];
for (NSDictionary *item in arr1) {
map[item[#"id"]] = item;
}
NSMutableArray *arr3 = [NSMutableArray array];
for (id key in arr2) {
[arr3 addObject:map[key]];
}
This solution of course assumes parity between the two arrays. If arr2 has an element not in arr1 it will crash when trying to add nil to arr3. If arr1 has a value not in arr2 it will be excluded from arr3. These are risks you will have to address based on your requirements.
Here is how you can do it by using a custom comparator:
NSArray* sorted= [arr1 sortedArrayUsingComparator: ^NSComparisonResult(NSDictionary *obj1, NSDictionary *obj2) {
return [arr2 indexOfObject:obj1[#"id"]] - [arr2 indexOfObject:[obj2[#"id"]];
}];
I exploited the fact that NSComparisonResult has +1 to represent an ascending order, -1 for descending and 0 to represent the same order.
- (NSArray*) sortedArray
{
NSArray *arr1 = #[#{#"id":#1},#{#"id":#2},#{#"id":#3},#{#"id":#4}];
NSArray *arr2 = #[#3,#1,#4,#2];
NSMutableArray *mutableArray = [NSMutableArray new];
for (NSNumber *number in arr2)
{
for (NSDictionary* dictionary in arr1)
{
NSNumber *number2 = dictionary[#"id"];
if ([number isEqual:number2])
{
[mutableArray addObject:dictionary];
break;
}
}
}
return mutableArray;
}
NSMutableDictionary *expense_ArrContents = [[NSMutableDictionary alloc]init];
for (int i = 1; i<=4; i++) {
NSMutableArray *current_row = [NSMutableArray arrayWithObjects:#"payer_id",#"Expense_Type_id",#"Category_Id",#"SubCategory_Id",nil];
[expense_ArrContents setObject:current_row forKey: [NSNumber numberWithInt:i]];
}
NSArray *newArray = [expense_ArrContents allKeysForObject:#"payer_id"];
NSLog(#"%#",[newArray description]);
i want to get the list of key values containing the particular object which is in the array of values stored in nsmutabledictionary for a particular key.
In the line where you get all the keys ([expense_ArrContents allKeysForObject:#"payer_id"];) you actually get keys for an object that is not in any of the array's items. This #"player_id" is different object than the #"player_id" you added in current_row. In fact, maybe all of your rows have different #"player_id" objects (except if the compiler has made some optimization - maybe it threats that same string literal as one object instead of creating new object for each iteration).
Try creating an NSString object for the #"player_id" which you add to the current_row and then get all the keys for that same object:
NSString* playerId = #"player_id";
for(){
NSMutableArray *current_row = [NSMutableArray arrayWithObjects: playerId,...];
...
}
NSArray *newArray = [expense_ArrContents allKeysForObject:playerId];
Your NSArray *newArray = [expense_ArrContents allKeysForObject:#"payer_id"]; will not return any value because in expense_ArrContents there is no such key(#"payer_id"), instead there are keys like 1,2,3 etc.What is your requirement?Want to see what all keys are there in expense_ArrContents just log
NSArray*keys=[expense_ArrContents allKeys];
Try this :
NSMutableArray *array_key=[[NSMutableArray alloc]init];
for (NSString *key in expense_ArrContents) {
if ([[expense_ArrContents objectForKey:key] containsObject:#"payer_id"]) {
[array_key addObject:key];
}
}
I am new to iOS and want to create an NSArray like this which contains an NSDictionary.
[
{
Image: 1, 2,3
Title: 1,2,3
Subtitle:1,2,3
}
]
I have tried this.
NSArray *obj-image=#[#"Test.png",#"Test.png",#"Test.png"];
NSArray *obj-title=#[#"Test",#"Test",#"Test"];
NSArray *obj-subtitle=#[#"Test",#"Test",#"Test"];
NSDictionary * obj_dictionary ={ image : obj_image, title:obj_title, subtitle:obj_subtitle}
NSArray * obj_array= [obj_dictionarry];
But not working and how to access them.
First of all, you initialization of Arrays and Dictionaries is wrong. You cannot use "-" in the names, period.
Second, you need to allocate and then initialize the objects. This is how you do that with arrays:
NSArray *images = [NSArray arrayWithObjects: #"TestImage",#"TestImage",#"TestImage",nil];
NSArray *titles = [NSArray arrayWithObjects: #"TestTitle",#"TestTitle",#"TestTitle",nil];
NSArray *subtitles = [NSArray arrayWithObjects: #"TestSubTitle",#"TestSubTitle",#"TestSubTitle",nil];
Then you need Mutable dictionary and mutable arrays to work with the data (mutable means you can change the values inside, add or remove objects etc.)
This is the most basic example of what you are trying to achieve:
NSArray *images = [NSArray arrayWithObjects: #"TestImage",#"TestImage",#"TestImage",nil];
NSArray *titles = [NSArray arrayWithObjects: #"TestTitle",#"TestTitle",#"TestTitle",nil];
NSArray *subtitles = [NSArray arrayWithObjects: #"TestSubTitle",#"TestSubTitle",#"TestSubTitle",nil];
NSMutableArray *objectsMutable = [[NSMutableArray alloc] init];
for (NSString *string in images) {
NSMutableDictionary *dictMutable = [[NSMutableDictionary alloc] init];
[dictMutable setObject:string forKey:#"image"];
//determining the index of the image
NSInteger stringIndex = [images indexOfObject:string];
[dictMutable setObject:[titles objectAtIndex:stringIndex] forKey:#"title"];
[dictMutable setObject:[subtitles objectAtIndex:stringIndex] forKey:#"subtitle"];
NSDictionary *dict = [[NSDictionary alloc] init];
dict = dictMutable;
[objectsMutable addObject:dict];
}
NSArray *objects = objectsMutable;
NSLog(#"%#", objects);
Hope this helps.
As you can see, I'm going through the images array, capturing the index of each one, an then just apply values of other arrays from the same index into a mutable dictionary.
All I do after that is just make a regular dictionary and array to put the data inside. This is ho the Log will look:
(
{
image = TestImage;
subtitle = TestSubTitle;
title = TestTitle;
},
{
image = TestImage;
subtitle = TestSubTitle;
title = TestTitle;
},
{
image = TestImage;
subtitle = TestSubTitle;
title = TestTitle;
}
)
You have an array with three objects inside, each with their own image, title and subtitle.
Here is code :
NSMutableArray *array = [[NSMutableArray alloc] init];
NSMutableDictionary *mdict = [[NSMutableDictionary alloc] initWithObjectsAndKeys:#"object1",#"key1",#"object2",#"key2",nil];
[array addObject:mDict];
so now if u need to access dictionary from array then :
NSMutableDictionary *mDict1 = [array objectatindex:0];
NSLog(#"%#",[mDict1 valueForkey:#"key1"];
--> print object 1.
This is the way to store array of dictionaries:
NSDictionary *dic=#{#"kishore":#"hai"};
NSMutableArray *arr=[[NSMutableArray alloc]init];
[arr addobject:dic];
this is the way to get those values:
[arr objectforkeyValue #"kishore"];
NSMutableArray *dictArray = [[NSMutableArray alloc] init]; // created and initiated mutable array
NSMutableDictionary *dict = [[NSMutableDictionary alloc] init]; // created and initiated mutable Dictionary
[dict setObject:#"object1" forKey:#"1"]; // added a key pair in dictionary (you can set multiple objects)
[dictArray addObject:dict]; // added dictionary to array (you can add multiple dictionary to array )
NSLog(#"dictionary inside an array : %#",dictArray[0][#"1"]); // access dictionary from array
You can try something like this
[NSArray arrayWithObjects:#{#"Image":#[#1,#2,#3]},#{#"Title":#[#1,#2,#3]},#{#"SubTitle":#[#1,#2,#3]}, nil];
You can easily create objects of array and access them back using following way.
NSArray *objimage=#[#"Test1.png",#"Test2.png",#"Test3.png"];
NSArray *objtitle=#[#"Test1",#"Test2",#"Test3"];
NSArray *objsubtitle=#[#"Test1",#"Test2",#"Test3"];
NSDictionary *obj_dictionary = #{#"image":objimage,#"Title":objtitle, #"subtitle":objsubtitle};
NSArray * obj_array= [[NSArray alloc] initWithObjects:obj_dictionary, nil]; // Create Array of nested objects
if([obj_array count] > 0) {
NSArray * imageArray = obj_array[0][#"image"]; // Access the nested objects in Array.
NSLog(#"%#", imageArray[0]);
}
first of all u need to declare correct variable name
NSArray *objImage=#[#"Test.png",#"Test.png",#"Test.png"];
NSArray *objTitle=#[#"Test",#"Test",#"Test"];
NSArray *objSubtitle=#[#"Test",#"Test",#"Test"];
at this point all u are created all the array, and u need to create dictionary like below
NSDictionary *obj_dictionary = #{#"image":objImage,#"title":objTitle, #"subtitle":objSubtitle};
// NSArray * obj_array = obj_dictionary[#"image"];
NSArray * obj_array = #[obj_dictionary]; //u can crate array of dictionary like this
in above obj_dictionary will contains all the array like below,
Title = (
Test,
Test,
Test
);
image = (
"Test.png",
"Test.png",
"Test.png"
);
subtitle = (
Test,
Test,
Test
);
and u can access the object in the dictionary like below using a key for example
NSArray * obj_array_images = obj_dictionary[#"image"];
gives an array of images that is associated with key image, similarly u can access other array like this by providing different keys associated with the dictionary obj_dictionary for example
NSArray * obj_array_titles = obj_dictionary[#"title"];
NSArray * obj_array_subtitles = obj_dictionary[#"subtitle"];
edit
NSArray *objImage=#[#"Test.png",#"Test.png",#"Test.png"];
NSArray *objTitle=#[#"Test",#"Test",#"Test"];
NSArray *objSubtitle=#[#"Test",#"Test",#"Test"];
NSDictionary *obj_dictionary = #{#"image":objImage,#"title":objTitle, #"subtitle":objSubtitle};
// NSArray * obj_array = obj_dictionary[#"image"];
NSArray * obj_array = #[obj_dictionary]; //u can crate array of dictionary like this