I'm trying to figure out the best way to sort an NSMutableDictionary. I have a dictionary of Card keys (i.e. aceSpades) that store Card values (i.e. 14). I have then been using an NSMutableArray to shuffle the 52 Card keys into an array called shuffledCards. Finally I make another array from shuffledCards thats takes a portion (15) of shuffledCards and puts them into an array called computerHand.
The new array computerHand is not good enough because I need to be able to connect the Card values with the Card keys. What I really need to do is create a new NSMutableDictionary for computerHand from the array shuffledCards so that I can sort it by Card values and still be able to retrieve the Card keys.
I'm thinking I need something like this, where currentCard is the first card of the shuffedCards array:
if (currentCard == 1) {
[compHandDictionary setObject:[[highCardDictionary
valueForKey:[shuffledCards objectAtIndex:currentCard]] intValue]
forKey:[cardsShuffled objectAtIndex:currentCard]];
}
However this is not allowed because "int" to "id" is not allowed.
There might be a better way but I have not been able to find anything. Any help would be appreciated.
...
I got this to work by modifying jstevenco's answer. I created two arrays and formed a new dictionary for the computer hand of just the 15 cards. Then to sort I used:
NSArray* sortedKeys = [newDict keysSortedByValueUsingComparator: ^(id obj1, id obj2) {
if ([obj1 integerValue] > [obj2 integerValue]) {
return (NSComparisonResult)NSOrderedAscending;
}
if ([obj1 integerValue] < [obj2 integerValue]) {
return (NSComparisonResult)NSOrderedDescending;
}
return (NSComparisonResult)NSOrderedSame;
}];
Thanks all!
You can sort a dictionary's keys using:
NSArray* sortedKeys = [[dict allKeys] sortedArrayUsingSelector:#selector(caseInsensitiveCompare:)];
If you then want to create a sorted array from this you can use:
NSArray* objects = [dict objectsForKeys:sortedKeys notFoundMarker:[NSNull null]];
Consider using an array of dictionaries, where each dictionary contains the name and value for a given card, for example like so:
NSArray *cards = #[#{#"name" : #"Queen", #"value" : #12},
#{#"name" : #"Jack", #"value" : #11},
#{#"name" : #"Ace", #"value" : #14},
#{#"name" : #"King", #"value" : #13}];
You could then easily sort the cards array as shown below:
NSSortDescriptor *sortDescriptor = [NSSortDescriptor sortDescriptorWithKey:#"value" ascending:YES];
NSArray *sortedCards = [cards sortedArrayUsingDescriptors:#[sortDescriptor]];
NSLog(#"\n\n%#\n\n", sortedCards);
Output of the NSLog statement above would be as follows:
(
{
name = Jack;
value = 11;
},
{
name = Queen;
value = 12;
},
{
name = King;
value = 13;
},
{
name = Ace;
value = 14;
}
)
To obtain an array of card names, you could then simply send a valueForKey: message to the sorted array of card dictionaries:
NSArray *sortedNames = [sortedCards valueForKey:#"name"];
NSLog(#"\n\n%#\n\n", sortedNames);
The output of the preceding NSLog statement would be:
(
Jack,
Queen,
King,
Ace
)
Related
I have NSDictionary with objects. The NSDictionary is consist of json(You can see it below). I need to populate my table view with the name by id. And the id can repeat. It means I can have several "name" with id which is equal 0. I should get name by key with certain value from the dictionary. Here is my NSDictionary:
{
name = "smth1";
id = 0;
},
{
name = "smth2";
id = 1;
},
{
name = "smth3";
id = 2;
},
{
name = "smth4";
id = 2;
},
...
For example, I want to get value of key "name" where id is 2. Then I will get name = "smth3" and name = "smth4". Generally, I am trying to populate my table view component with the nested data. How can I do this? Any tips, ideas. Thank you.
Actually you show an array of dictionaries, where each dictionary has 2 keys.
You could use the NSArray function indexOfObjectPassingTest. That code might look like this (starting from an NSArray) :
int idToFind = 2;
NSArray *dictArray = #[#{#"name": #"smth1",
#"id": #(0)},
#{#"name": #"smth2",
#"id": #(1)},
#{#"name": #"smth3",
#"id": #(2)}
];
NSUInteger dictIndex =
[dictArray indexOfObjectPassingTest: ^BOOL(
NSDictionary *dict,
NSUInteger idx,
BOOL *stop) {
return [dict[#"id"] intValue] == idToFind;
}];
if (dictIndex != NSNotFound) {
NSLog(#"Found id %d with name %#", idToFind, dictArray[dictIndex][#"name"]);
}
}
EDIT:
If you need to match all of the items then you need to use the NSArray method indexesOfObjectsPassingTest. That finds all the items in an array that match.
That code would look like this:
int idToFind = 2;
NSArray *dictArray = #[#{#"name": #"smth1",
#"id": #(0)},
#{#"name": #"Fred",
#"id": #(2)},
#{#"name": #"smth2",
#"id": #(1)},
#{#"name": #"smth3",
#"id": #(2)},
];
NSIndexSet *dictIndexes;
dictIndexes =
[dictArray indexesOfObjectsPassingTest: ^BOOL(NSDictionary *dict,
NSUInteger idx,
BOOL *stop)
{
return [dict[#"id"] intValue] == idToFind;
}];
if (dictIndexes.count == 0) {
NSLog(#"No matches found");
}
[dictIndexes enumerateIndexesUsingBlock:^(NSUInteger index,
BOOL * _Nonnull stop)
{
NSLog(#"Found id=%# with name \"%#\" at index %lu",
dictArray[index][#"id"],
dictArray[index][#"name"],
index);
}];
Both approaches above use methods that take a block. The block contains code that you write that returns a BOOL for the item(s) that match your desired search criteria.
Search/sort methods that take blocks are very flexible because you can provide any code you want to do the matching/comparison.
The indexOfObjectPassingTest method searches for a single object in your array and stops when it finds the first match.
In contrast, the indexesOfObjectsPassingTest function will match multiple items. It returns an NSIndexSet, a special class that's used to index into NSArrays.
There is a function enumerateIndexesUsingBlock that invokes a block of code for each index specified in the array.
We could also have used the method objectsAtIndexes to extract only the elements in the array that are listed in the resulting index set, and then used for...in to loop through the items. That code would look like this:
NSArray *filteredArray = [dictArray objectsAtIndexes: dictIndexes];
for (NSDictionary *aDict in filteredArray) {
NSLog(#"Found id=%# with name \"%#\"", aDict[#"id"], aDict[#"name"]);
}
Note that this sort of thing is simpler and cleaner in Swift. We could use a filter statement on the array and provide a closure that selects items that match our search criteria
I have a Person NSDictionary, whose key is the Name of the person, and the object is an NSDictionary with two keys: his nickname (NSString) and his age (NSNumber).
I would like to end up with the Person dictionary sorted by the ascending order of their age, so that I could get the name of the youngest and the oldest person.
What is the best way to do it?
Thanks!
There are a few convenience methods defined in NSDictionary to sort items by values and get back the sorted keys.
See docs,
keysSortedByValueUsingComparator:
keysSortedByValueUsingSelector:
keysSortedByValueWithOptions:usingComparator:
I'm guessing you're using the modern Objective-C syntax and the age is actually represented as numbers. Here's how it looks:
[people keysSortedByValueUsingComparator:(NSDictionary *firstPerson, NSDictionary *secondPerson) {
return [firstPerson[#"age"] compare:secondPerson[#"age"]];
}];
Some languages offer sorted dictionaries, but the standard NSDictionary is inherently unsorted. You can get all the keys, sort the key array and then walk over the dictionary according to the sorted keys. (NSDictionary has several convenience methods for this use case that I didn’t know about, see Anurag’s answer.)
Your case is a bit more complex, one way to solve it is to introduce a temporary dictionary mapping ages to names. But if you’re only after the minimum and maximum ages, just iterate over all persons and keep track of the maximum & minimum ages and names:
NSString *oldestName = nil;
float maxAge = -1;
for (NSString *name in [persons allKeys]) {
NSDictionary *info = persons[name];
float age = [info[#"age"] floatValue];
if (age > maxAge) {
oldestName = info[#"nick"];
maxAge = age;
}
}
And if we get back to the idea of sorting the dictionary, this could work:
NSArray *peopleByAge = [people keysSortedByValueUsingComparator:^(id a, id b) {
// Again, see Anurag’s answer for a more concise
// solution using the compare: method on NSNumbers.
float ageA = [a objectForKey:#"age"];
float ageB = [b objectForKey:#"age"];
return (ageA > ageB) ? NSOrderedDescending
: (ageB > ageA) ? NSOrderedAscending
: NSOrderedSame;
}];
As #Zoul said the standard NSDictionary is unsorted.
To sort it you can use an array, and I do things like that
//the dictionary is called dict : in my case it is loaded from a plist file
NSDictionary *dict = [[NSDictionary alloc] initWithContentsOfFile:plistPath];
//make a dicoArray that is sorted so the results are sorted
NSArray *dicoArray = [[dict allKeys] sortedArrayUsingComparator:^(id firstObject, id secondObject) {
return [((NSString *)firstObject) compare:((NSString *)secondObject) options:NSNumericSearch];
}];
check the help for all the sort options. In the presented case the dictionary is sorted with keys treated as numeric value (which was the case for me).
If you need to sort another way the list of sort possibilities is
enum {
NSCaseInsensitiveSearch = 1,
NSLiteralSearch = 2,
NSBackwardsSearch = 4,
NSAnchoredSearch = 8,
NSNumericSearch = 64,
NSDiacriticInsensitiveSearch = 128,
NSWidthInsensitiveSearch = 256,
NSForcedOrderingSearch = 512,
NSRegularExpressionSearch = 1024
};
In iOS 9.2
// Dictionary of NSNumbers
NSDictionary * phoneNumbersDict = #{#"400-234-090":67,#"701-080-080":150};
// In Ascending Order
NSArray * keysArraySortedByValue = [phoneNumbersDict keysSortedByValueUsingComparator:^NSComparisonResult(id _Nonnull obj1, id _Nonnull obj2) {
return [obj1 compare:obj2];
}];
// In Descending Order
NSArray * keysArraySortedByValue = [phoneNumbersDict keysSortedByValueUsingComparator:^NSComparisonResult(id _Nonnull obj1, id _Nonnull obj2) {
return [obj2 compare:obj1];
}];
Here is the enum for NSComparisonResults.
enum {
NSOrderedAscending = -1,
NSOrderedSame,
NSOrderedDescending
};
typedef NSInteger NSComparisonResult;
Look at the NSDictionary's method that returns keys sorted by a selector. There are more than one such method. You get an array of sorted keys, then access the first and last and have your youngest and oldest person.
I have an NSArray containing several NSDictionary instances. Each NSDictionary has, among other fields, an object named rating and one numberOfVotes(both are int). How can I sort the array so it gets sorted by rating/numberOfVotes? More generically, can I sort it by doing an operation like mentioned above? Or would it be better to just add another object to each NSDictionary with the value of each operation and then sort by that?
Thanks
EDIT - I have added the following. Still not sorting properly. One question: Should this work for more than 2 objects in my array. (The number of objects will vary)
[sortedArray sortedArrayUsingComparator:^NSComparisonResult(id dict1, id dict2)
{
MyObj *obj1 = (MyObj *)dict1;
MyObj *obj2 = (MyObj *)dict2;
int rating1 = obj1.rating.intValue;
int rating2 = obj2.rating.intValue;
int number1 = obj1.number_of_votes.intValue;
int number2 = obj2.number_of_votes.intValue;
double key1 = ((double)rating1)/number1;
double key2 = ((double)rating2)/number2;
if (key1 < key2)
{
return NSOrderedDescending;
}
if (key2 < key1)
{
return NSOrderedAscending;
}
return NSOrderedSame;
}];
You can define a custom comparator to use a composite sorting key of the kind that you are looking for. If there is no good reason to have that sorting key in the dictionary, other than performing the sort, do not add an item to the dictionary.
array = [array sortedArrayUsingComparator: ^(id obj1, id obj2) {
int rating1 = [[obj1 objectForKey:#"rating"] intValue];
int numberOfVotes1 = [[obj1 objectForKey:#"numberOfVotes"] intValue];
int rating2 = [[obj2 objectForKey:#"rating"] intValue];
int numberOfVotes2 = [[obj2 objectForKey:#"numberOfVotes"] intValue];
double key1 = ((double)rating1)/numberOfVotes1;
double key2 = ((double)rating2)/numberOfVotes2;
if (key1 > key2) {
return (NSComparisonResult)NSOrderedDescending;
}
if (key1 < key2) {
return (NSComparisonResult)NSOrderedAscending;
}
return (NSComparisonResult)NSOrderedSame;
}];
Note: The sortedArrayUsingComparator: method does not sort the array in place; instead, it returns a sorted copy. If you would like an in-place sorting, use NSMutableArray.
The adequate way would be using blocks like this
NSArray *sortedArray;
sortedArray = [unsortedArray sortedArrayUsingComparator:^NSComparisonResult(id a, id b) {
float first = [[(NSDictionary*)a objectForKey:#"rating"] floatValue]/
[[(NSDictionary*)a objectForKey:#"numberOfVotes"] floatValue];
float second = [[(NSDictionary*)a objectForKey:#"rating"] floatValue]/
[[(NSDictionary*)a objectForKey:#"numberOfVotes"] floatValue];
return [[NSNumber numberWithFloat:first] compare: [NSNumber numberWithFloat:second]];
}];
you may find more ways to compare:
How to sort an NSMutableArray with custom objects in it?
The family of methods you seek are prefixed with sortedArray.
For a function (which is one of multiple options), see: -[NSArray sortedArrayUsingFunction:context:].
Edit: If you want to do rating divided by numberOfVotes, you will have to sort by a function or comparator block or replace the dictionary with a model object which has a method to calculate rating / numberOfVotes.
Use NSSortDescriptor.
NSArray *sorted = [array sortedArrayUsingDescriptors:[NSArray arrayWithObjects:
[NSSortDescriptor sortDescriptorWithKey:#"rating" ascending:YES],
[NSSortDescriptor sortDescriptorWithKey:#"numberOfVotes" ascending:YES],
nil]
];
Filtering data is one of the essential tasks in computing.
You can sort it several ways.
NSPredicate
You can see examples here
NSSortDescriptor
You can see examples here
Regular Expressions
Set Operations
Key-Value Coding
Ideally, you should substitute NSDictionary by a custom object, with properties like rating and numberOfVotes. Then, you could declare a method compare: on this custom object and use as the selector to sort the array.
You can use a block code to sort the objects but abstracting the implementation into a custom object is much cleaner.
you can use NSSortDescriptor here for sorting for example your array that containing several NSDictionnaries name is dataArray.
NSSortDescriptor * descriptor = [[NSSortDescriptor alloc] initWithKey:rating
ascending:YES];
NSArray * keyArrray = [NSArray arrayWithObjects:descriptor, nil];
NSArray * sortedArray = [dataArray sortedArrayUsingDescriptors:keyArrray];
With the help of NSSortDescriptor we can sort any data type key value pair.
I want to sort a NSMutableArray which has NSArrays with respect to the value at the index 1 of the NSArray. I'll try to draw a picture of arrays.
NSMutableArray *ultimateHighscoreArray = {
( (NSString) userName, (double) score, (int) numOfCorrectAnswers ) ,
( John , 4.5 , 3 ) ,
( Terry , 7.5 , 1) ,
... }
The first array within the NSMutableArray is an example which shows how examples are located. Second and third are how the values actually are. So, what I want is to sort these arrays having the array containing higher value at first index to go higher up in the ranking. For this example the array that has 7.5 which is Terry Array should go before the one that has 4.5 . I want the results to be held in a NSMutableArray in decreasing order. Thank you.
This should do it:
[ultimateHighscoreArray sortUsingComparator:^(id obj1, id obj2) {
NSNumber *score1 = [obj1 objectAtIndex:1];
NSNumber *score2 = [obj2 objectAtIndex:2];
// Reverse the comparison here (compare score2 to score1)
// in order to get a descending order
return [score2 compare:score1];
}];
A general advice: your data structure would be clearer if it were an array of NSDictionary instances or even an array of custom objects (e.g., your custom Score class). In those cases, you could also use NSSortDescriptor to sort the array, which would result in cleaner, easier-to-read code.
The sortUsingComparator: method allows you to sort an array using a block, e.g.:
[ultimateHighscoreArray sortUsingComparator:^(id obj1, id obj2) {
return [[obj1 objectAtIndex:1] compare:[obj2 objectAtIndex:1]];
}];
For clarity, it would probably be better to use an array of dictionaries (or instances of a custom class) for this data structure.
You can write a custom comparator like this :)
[ultimateHighscoreArray sortUsingComparator:^NSComparisonResult(id obj1, id obj2) {
NSArray *arrayA = (NSArray *)obj1;
NSArray *arrayB = (NSArray *)obj2;
double scoreA = [arrayA objectAtIndex:1];
double scoreB = [arrayB objectAtIndex:1];
if (scoreA > scoreB) {
return NSOrderedDescending;
} else if (scoreA < scoreB) {
return NSOrderedAscending;
} else {
return NSOrderedSame;
}
}];
I know there are many topics with similar issues, but I have not been able to find a topic addressing my question.
I want to store a plist of highscores.
Every entry of highscores must have two elements
an NSString* and an int.
I want to store the top 20 high scores (pairs of strings and ints) and do that in a plist.
I start with:
NSMutableArray *arr = [[NSMutableArray alloc] initWithContentsOfFile: [[NSBundle mainBundle] pathForResource:#"Mylist" ofType:#"plist"]];
I want the item 0 of the array to be a dictionary, where I can insert key value pairs of
(string, int)
How do I do that?
You can always call [arr addObject:score];, sort it, and remove the final item until there are 10.
To sort:
[arr sortUsingComparator:^(id firstObject, id secondObject) {
NSDictionary *firstDict = (NSDictionary *)firstObject;
NSDictionary *secondDict = (NSDictionary *)secondObject;
int firstScore = [[firstDict objectForKey:#"score"] intValue];
int secondScore = [[secondDict objectForKey:#"score"] intValue];
return firstScore < secondScore ? NSOrderedAscending : firstScore > secondScore : NSOrderedDescending : NSOrderedSame;
}];
If you want the scores to be the other way around, change the '>' to '<' and vice-versa. To keep the list down to 10:
while ([arr count] > 10) {
[arr removeLastObject];
}
You may have to sort when you load from your plist. For 10 scores the performance hit will be minimal, so I suggest you do it just in case.
Property List Serialization
You will want to make notice of: the mutability option, as your method probably returns immutable arrays...
storing in a plist is done with the writeToFile:... or writeToURL:... methods
[arr insertObject:[NSMutableDictionary dictionary] atIndex:0];