NSLog(#"Ci sono %d categorie",category.count);
for(int c=0; c<category.count; c++){
CategoryArray * element =[category objectAtIndex:c];
NSLog(#"******************************");
NSLog(#"Titolo %#",element.label);
NSLog(#"Source %#",element.url);
NSLog(#"******************************");
[element release];
This is my code! I need to remove all duplicates array... I use this code but I don't understand why it doesn't work.
uniquearray = [[NSSet setWithArray:category] allObjects];
Your code does work. Try this:
NSArray *a = [NSArray arrayWithObjects:#"a", #"b", #"c", #"d", #"b", #"b", #"d", nil];
NSLog(#"a: %#\ndistinctA: %#", a, [[NSSet setWithArray:a] allObjects]);
The output is:
a: (
a,
b,
c,
d,
b,
b,
d
)
distinctA: (
c,
d,
a,
b
)
Knowing that the code works for an array that contains duplicate objects, you now have to wonder why objects that you think are duplicates are not considered to be so. The existing answers regarding hash and isEqual point you in the right direction.
The elements inside this CategoryArray must correctly implement isEqual and hash for the NSSet object to be able to figure out which ones are duplicates.
You can see another SO question about overriding isEqual and hash here: Best practices for overriding isEqual: and hash
Set can not contain any duplicate records. It uses a hash to tell them apart and will use isEqual if the hash is same (see the comment by Rudy Velthuis).
you can use following code.
NSMutableArray* filterResults = [[NSMutableArray alloc] init];
BOOL copy;
if (![category count] == 0) {
for (CategoryArray *a1 in category) {
copy = YES;
for (CategoryArray *a2 in filterResults) {
if ([a1.label isEqualToString:a2.label] && [a1.url isEqualToString:a2.url]) {
copy = NO;
break;
}
}
if (copy) {
[filterResults addObject:a1];
}
}
}
And you will get category array without duplicate values.
you can see Edit code. i think this will work.
If you are worried about the order, then you can do it this way.
NSArray * newArray = [[NSOrderedSet orderedSetWithArray:oldArray] array]; // iOS 5.0 and later
Related
This question already has answers here:
Closed 10 years ago.
Possible Duplicate:
Generating permutations of NSArray elements
Let's say that I have
[1,2]
And I want to get
{1}
{2}
{1, 2}
{2, 3}
I think the name of the thing you're looking for is 'power set'. It sounded fun, so here's a crack at it. I relied on this very concise article for the algorithm. I'm not sure if this is efficient (...actually, I'm sure this is inefficient) over large sets.
// answer the powerset of array: an array of all possible subarrays of the passed array
- (NSArray *)powerSet:(NSArray *)array {
NSInteger length = array.count;
if (length == 0) return [NSArray arrayWithObject:[NSArray array]];
// get an object from the array and the array without that object
id lastObject = [array lastObject];
NSArray *arrayLessOne = [array subarrayWithRange:NSMakeRange(0,length-1)];
// compute the powerset of the array without that object
// recursion makes me happy
NSArray *powerSetLessOne = [self powerSet:arrayLessOne];
// powerset is the union of the powerSetLessOne and powerSetLessOne where
// each element is unioned with the removed element
NSMutableArray *powerset = [NSMutableArray arrayWithArray:powerSetLessOne];
// add the removed object to every element of the recursive power set
for (NSArray *lessOneElement in powerSetLessOne) {
[powerset addObject:[lessOneElement arrayByAddingObject:lastObject]];
}
return [NSArray arrayWithArray:powerset];
}
If you think this is a keeper, you could make it a category method on array and drop the parameter. Test it like this...
NSLog(#"empty = %#", [self powerSet:[NSArray array]]);
NSLog(#"one item = %#", [self powerSet:[NSArray arrayWithObject:#"a"]]);
NSLog(#"two items = %#", [self powerSet:[NSArray arrayWithObjects:#"a", #"b", nil]]);
NSLog(#"three items = %#", [self powerSet:[NSArray arrayWithObjects:#"a", #"b", #"c", nil]]);
I did only these tests, and the output looked good. Spoiler alert: the three item test looks roughly like this on my console (with \n's removed):
three items = ((),
(a),
(b),
(a,b),
(c),
(a,c),
(b,c),
(a,b,c))
I am attempting to use this array cleaning method, and there seems to be an error. I can't spot it, I know the array goes in with 3116 items, comes out with 3116 (and I know for a fact there are three duplicates.
Please advice, thanks!
-(NSArray*) removeDuplicates:(NSArray*)inputArray{
NSMutableArray *arrayToClean = [NSMutableArray arrayWithArray:inputArray];
for (int i =0; i<[arrayToClean count]; i++) {
for (int j=(i+1); j < [arrayToClean count]; j++) {
if ([[arrayToClean objectAtIndex:i] isEqual:[arrayToClean
objectAtIndex:j]]) {
[arrayToClean removeObjectAtIndex:j];
j--;
}
}
}
NSArray *arrayToReturn = [NSArray arrayWithArray:arrayToClean];
return arrayToReturn;
}
NSSet will make this a lot easier:
-(NSArray *)removeDuplicates:(NSArray *)inputArray {
NSSet *unique = [NSSet setWithArray:inputArray];
return [unique allObjects];
}
Please note that a set has no guaranteed order. If you need the objects in the array to be in a specific order then you should sort the resulting array as needed.
It may also be appropriate to use an NSSet instead of the original array, then you don't need to worry about duplicates at all. But this depends on the other needs of your array.
Hey You can use another alternative for this.You can use the NSSet here for this task.
NSSet declares the programmatic interface for static sets of distinct objects
You can use sets as an alternative to arrays when the order of elements isn’t important and performance in testing whether an object is contained in the set is a consideration—while arrays are ordered, testing for membership is slower than with sets.
You Just need To call below method.
-(NSArray *)removeDuplicates:(NSArray *)inputArray {
NSSet *finalData = [NSSet setWithArray:inputArray];
return [finalData allObjects];
}
If really face any problem in above way of cleaning ducplicates then you can try another Alterantive.
-(NSArray *)removeDuplicates:(NSArray *)inputArray {
NSMutableArray *inputArray1=[NSMutableArray arrayWithArray:inputArray];
NSMutableArray *finalARray=[[NSMutableArray alloc]init];
for (id obj in inputArray1)
{
if (![finalARray containsObject:obj])
{
[finalARray addObject: obj];
}
NSLog(#"new array is %#",finalARray);
}
return finalARray;
}
I hope it may help you ...
Here is a helper function I had in a previous project to do the exact same thing
- (NSMutableArray *)removeDuplicates:(NSMutableArray *)sortedArray{
NSMutableSet* valuesAdded = [NSMutableSet set];
NSMutableArray* filteredArray = [[NSMutableArray alloc] init];
NSString* object;
/* Iterate over the array checking if the value is a member of the set. If its not add it
* to the set and to the returning array. If the value is already a member, skip over it.
*/
for (object in sortedArray){
if (![valuesAdded member:object]){
[valuesAdded addObject:object];
[filteredArray addObject:object];
}
}
return filteredArray;
}
I want to get the index of an object within the NSMutableArray of categories.
The category object has an attribute "category_title" and I want to be able to get the index by passing the value of category_title.
I have looked through the docs and can't find a simple way to go about this.
NSArray does not guarantee that you can only store one copy of a given object, so you have to make sure that you handle that yourself (or use NSOrderedSet).
That said, there are a couple approaches here. If your category objects implement isEqual: to match category_title, then you can just use -indexOfObject:.
If you can't do that (because the category objects use a different definition of equality), use -indexOfObjectPassingTest:. It takes a block in which you can do whatever test you want to define your "test" - in this case, testing category_title string equality.
Note that these are all declared for NSArray, so you won't see them if you are only looking at the NSMutableArray header/documentation.
EDIT: Code sample. This assumes objects of class CASCategory with an NSString property categoryTitle (I can't bring myself to put underscores in an ivar name :-):
CASCategory *cat1 = [[CASCategory alloc] init];
[cat1 setCategoryTitle:#"foo"];
CASCategory *cat2 = [[CASCategory alloc] init];
[cat2 setCategoryTitle:#"bar"];
CASCategory *cat3 = [[CASCategory alloc] init];
[cat3 setCategoryTitle:#"baz"];
NSMutableArray *array = [NSMutableArray arrayWithObjects:cat1, cat2, cat3, nil];
[cat1 release];
[cat2 release];
[cat3 release];
NSUInteger barIndex = [array indexOfObjectPassingTest:^BOOL(id obj, NSUInteger idx, BOOL *stop) {
if ([[(CASCategory *)obj categoryTitle] isEqualToString:#"bar"]) {
*stop = YES;
return YES;
}
return NO;
}];
if (barIndex != NSNotFound) {
NSLog(#"The title of category at index %lu is %#", barIndex, [[array objectAtIndex:barIndex] categoryTitle]);
}
else {
NSLog(#"Not found");
}
Not sure that I understand the question but something like this might work (assuming the Mutable Array contains objects of Class "Category"):
int indx;
bool chk;
for (Category *aCategory in theArray)
{
chk = ([[aCategory category_title] isEqualToString:#"valOfCategoryTitle"])
if ( chk )
indx = [theArray indexOfObject:aCategory];
}
Try this code much more simpler:-
int f = [yourArray indexOfObject:#"yourString"];
The title pretty much says it all, but just to clarify: I have an NSMutableDictonary containing several NSMutableArrays. What I would like to do is find any value that is present in multiple arrays (there will not be any duplicates in a single array) and return that value. Can someone please help? Thanks in advance!
Edit: For clarity's sake I will specify some of my variables:
linesMutableDictionary contains a list of Line objects (which are a custom NSObject subclass of mine)
pointsArray is an array inside each Line object and contains the values I am trying to search through.
Basically I am trying to find out which lines share common points (the purpose of my app is geometry based)
- (NSValue*)checkForDupes:(NSMutableDictionary*)dict {
NSMutableArray *derp = [NSMutableArray array];
for (NSString *key in [dict allKeys]) {
Line *temp = (Line*)[dict objectForKey:key];
for (NSValue *val in [temp pointsArray]) {
if ([derp containsObject:val])
return val;
}
[derp addObjectsFromArray:[temp pointsArray]];
}
return nil;
}
this should work
If by duplicates you mean returning YES to isEqual: you could first make an NSSet of all the elements (NSSet cannot, by definition, have duplicates):
NSMutableSet* allElements = [[NSMutableSet alloc] init];
for (NSArray* array in [dictionary allValues]) {
[allElements addObjectsFromArray:array];
}
Now you loop through the elements and check if they are in multiple arrays
NSMutableSet* allDuplicateElements = [[NSMutableSet alloc] init];
for (NSObject* element in allElements) {
NSUInteger count = 0;
for (NSArray* array in [dictionary allValues]) {
if ([array containsObject:element]) count++;
if (count > 1) {
[allDuplicateElements addObject:element];
break;
}
}
}
Then you have your duplicate elements and don't forget to release allElements and allDuplicateElements.
I have an array, which contains some duplicate entries.
Firstly, is there any way to restrict duplicate entries when data getting inserted?
Secondly, if an array already having duplicate values than in some other way, we can retrieve only unique values from that array, I heard about NSSet about this, but I have no idea how to use it.
Don't use an NSSet.
You can only insert elements upon creation and cannot change the elements contained after you have created it.
If you want to add and remove objects on the fly, you can use an NSMutableSet.
Here is a demo of how to use it both NSSet and NSMutableSet, then converting the NSSet back to an NSArray (incase you want to do that):
- (void) NSMutableSetPrintTest
{
NSMutableSet *mutableSet = [[NSMutableSet alloc] init];
NSLog(#"Adding 5 objects (3 are duplicates) to NSMutableSet");
NSString *firstString = #"Hello World";
[mutableSet addObject:firstString];
[mutableSet addObject:#"Hello World"];
[mutableSet addObject:#"Goodbye World"];
[mutableSet addObject:#"Goodbye World"];
[mutableSet addObject:#"Goodbye World"];
NSLog(#"NSMutableSet now contains %d objects:", [mutableSet count]);
int j = 0;
for (NSString *string in mutableSet) {
NSLog(#"%d: %# <%p>", j, string, string);
j++;
}
NSLog(#"Now, if we are done adding and removing things (and only want to check what is in the Set) we should convert to an NSSet for increased performance.");
NSSet *immutableSet = [NSSet setWithSet:mutableSet];
NSLog(#"NSSet now contains %d objects:", [immutableSet count]);
int i = 0;
for (NSString *string in immutableSet) {
NSLog(#"%d: %# <%p>", i, string, string);
i++;
}
[mutableSet release]; mutableSet = nil;
NSLog(#"Now, if we are done with the sets, we can convert them back to an NSArray:");
NSArray *array = [immutableSet allObjects];
NSLog(#"NSArray contains %d objects", [array count]);
int k = 0;
for (NSString *string in array) {
NSLog(#"%d: %# <%p>", k, string, string);
k++;
}
}
NSMutableSet is probably the most logical thing to use.
However, be warned that a set does not maintain order of its elements (since a set, by definition, is unordered).
If that's a problem for you, then you have a couple of options:
duplicate set functionality with an NSMutableArray by invoking containsObject: before every call to addObject: (doable, but potentially slow, since arrays have O(n) search time)
use another object.
If you go with the second option, I would recommend taking a look at the excellent CHDataStructures framework, which has a subclass of NSMutableSet called CHOrderedSet, which is a set that maintains insertion order. (And since it's a subclass, it has the exact same API as an NSMutableSet)
If you've heard about NSSet, did you read the documentation? The API is similar to NSArray and very straightforward. Just like NSArray vs. NSMutableArray, you would use NSMutableSet if you need on the fly membership tests.