So we're converting some old code and I need to change
NSSet *set = [NSOrderedSet orderedSetWithOrderedSet:filteredSubcategories
range:[range rangeValue]
copyItems:NO];
into an array. Is there some kind of array equivalent to this? Can someone help me do this?
https://developer.apple.com/reference/foundation/nsorderedset/1543292-orderedsetwithorderedset
Please see below a solution, but please check the initial purpose of using Set instead of Array in the original code. The change that you are going to make may reduce performance if originally using set is:
To prevent duplicate or if there is a check if an object exist inside a loop.. Array and Set have the same method name contains: but a huge difference on performance.
for (NSNumber *number in myArray) {
if([myArrayOfCategories containsObject:#9]){ //O(n) worst look up
///do sthg
}
}
for (NSNumber *number in myArray) {
if([mySetOfCategories containsObject:#9]){ //O(1) fast lookup
///do sthg
}
}
//Solution
NSIndexSet *indexSet = [NSIndexSet indexSetWithIndexesInRange:NSMakeRange(1, 3)];
NSArray* content = [filteredSubcategories objectsAtIndexes:indexSet];
Either create set as in the OP and get its array representation, like this:
NSSet *set = [NSOrderedSet orderedSetWithOrderedSet:filteredSubcategories //... as in the OP
NSArray *array = [set array];
Or, if you don't need the set, just subrange filteredSubcategories array representation, like this:
NSArray *array = [[filteredSubcategories array] subarrayWithRange:[range rangeValue]];
Related
I have an object containing an array of NSNumbers (indexes) and an array of NSDictionaries (indexesTitles) corresponding to indexes, containing some info.
I have to call a method for each object.index and associate object.indexTitles to the returning results, saving them into a single array.
At the end of it, I want to remove indexes duplicates, preserving the associated indextTitles in an efficient way, because I'm working with large arrays.
NSMutableArray *resultArray = [NSMutableArray array];
NSMutableArray *titlesArray = [NSMutableArray array];
for(NSNumber *index in object.indexes)
{
NSArray *resultsIndexArray = [self methodThatReturnsAnArray];
NSString *indexTitleDictionary = [object.indexesTitles objectAtIndex:i];
for(NSNumber *resultId in resultsIndexArray)
{
[titlesArray addObject:indexDictionary];
[resultArray addObject:resultId];
}
i++;
}
[fullResultsArray addObject:titlesArray];
[fullResultsArray addObject:resultArray];
I've found that the most efficient way to remove duplicates is using an
NSOrderedSet like this:
NSOrderedSet *orderedSet = [NSOrderedSet orderedSetWithArray:resultArray];
resultArray = [orderedSet.array mutableCopy];
How can I remove the corresponding entries in titlesArray? how can I preserve the association?
I've also tried to use a NSDictionary like {resultId, titleDictionary} and storing them into an array, but I haven't found a efficient way to remove dictionaries with the same result, they are all too slow.
Any suggestion?
It is not completely clear to me what your problem is, maybe this will help:
A good way to remove duplicates is not to add them in the first place, replace:
for(NSNumber *resultId in resultsIndexArray)
{
[titlesArray addObject:indexDictionary];
[resultArray addObject:resultId];
}
with:
for(NSNumber *resultId in resultsIndexArray)
{
// only add if resultId not already in resultArray
if( ![resultArray containsObject:resultId] )
{
[titlesArray addObject:indexDictionary];
[resultArray addObject:resultId];
}
}
The containsObject: call requires a linear search, if your data set is large you might wish to change resultArray to an NSMutableSet and titlesArray to an NSMutableDictionary mapping from resultId to indexDictionary values.
HTH
I have a UITableView and am displaying contents from my NSMutableArray. Following is array format
(
{
Name = "ANS";
VersionNo = 6;
},
{
Name = "O-Hydro";
Version = 6;
},
{
Name = "ANS";
Version = 6;
},
{
Name = "ANTIChorosAnticholinergic";
Version = 6;
}
)
From this I need to display only unique "Name" (like in this I can see 2 "ANS" I need only one).
How can I do this in iOS?
I tried following but its not working
uniqueArray= [[NSMutableSet setWithArray: groupDetails] allObjects];
but in this way I can do only for NSArray not NSMutableArray.
Pls help me
You can use following line of code to convert your NSArray to NSMutableArray,
NSArray *uniqueArray= [[NSMutableSet setWithArray:groupDetails] allObjects];
NSMutableArray *myMutableArray = [[NSMutableArray alloc] initWithArray:uniqueArray];
You could simply add mutableCopy.
But wait, before you do it. Arrays and sets have two differences:
Arrays can contain duplicates, sets cannot.
Arrays are ordered, sets are not.
So doing what you are doing, you lose the duplicates (intentionally), but the order, too (probably not intentionally).
I do not know, whether this is important for you, but for other readers it might be. So it is the better approach to do that with NSOrderedSet instead of NSSet:
NSOrderedSet *uniqueList = [NSOrderedSet orderedSetWithArray:array];
In many cases an ordered set is exactly what you want. (Probably it has been from the very beginning and the usage of NSArray was wrong. But sometimes you get an array.) If you really want an array at the end of the day, you can reconvert it:
array = [uniqueList.array mutableCopy];
If you just want an array of unique name values, you can use #distinctUnionOfObjects with valueForKeyPath -
NSArray *uniqueArray=[groupDetails valueForKeyPath:#"#distinctUnionOfObjects.name"];
But if you want the array to contain the dictionaries that correspond to the unique names then you need to do a little more work -
NSMutableArray *uniqueArray=[NSMutableArray new];
NSMutableSet *nameSet=[NSMutableSet new];
for (NSDictionary *dict in groupDetails) {
NSString *name=dict[#"name"];
if (![nameSet containsObject:name]) {
[uniqueArray addObject:dict];
[nameSet addObject:name];
}
}
I have an NSarray called array. And it look like this
array = #[#"one", #"two", #"three"];
I want this array to be capitalized. What is the best way to go about this. I can only think of making an NSMutableArray called mutableArray.
And do something like this
for(int i = 0; i < array.lenght; i++) {
self.mutableArray = addObject:[array[i] capitalizedString];
}
Or is there another better way?
The magic method you are looking for does in fact exist.
NSArray *array = #[#"one", #"two", #"three"];
NSArray *capArray = [array valueForKeyPath:#"capitalizedString"];
SWIFT
You Can use map
let array = ["one", "two", "three"]
let upercaseArray = array.map({$0.uppercased()})
now you have upercaseArray like ["ONE","TWO","THREE""]
What you really want is a sort of transform method, which takes an array and a selector, then returns an array of the results of performing that selector on each object. Unfortunately that doesn't exist in vanilla objective-C.
Your approach is generally fine, but I would be careful of two points. Firstly, make sure you create the NSMutableArray with the capacity of the NSArray you are copying, as this will avoid any reallocation overhead as you add objects to it. Secondly, you might want to copy the mutable array so you end up with an immutable NSArray as the final result.
So I would use something like this:
- (NSArray *)capitalizeStringArray:(NSArray *)array {
// Initialize tempArray with size of array
NSMutableArray *tempArray = [NSMutableArray arrayWithCapacity:array.count];
for (NSString *str in array) {
[tempArray addObject:[str capitalizedString]];
}
return [tempArray copy]; // convert back to NSArray]
}
You can convert this to a category method on NSArray if you like, and generalize it to use other selectors if you wish.
There's about a gazillion ways to handle this. For small arrays, pick whichever you find easier to understand.
I'd probably use code like this:
- (NSMutableArray *) capitalizedArrayFromArrayOfStrings: (NSArray*) array;
{
NSMutableArray *result = [NSMutableArray arrayWithCapacity: array.count];
for (NSString *string in array)
{
if ([string isKindOfClass: [NSString class]]
[result addObject: [string capitalizedString];
}
}
Creating your array with the correct capacity at the beginning enables the array to allocate enough space for all it's future elements and saves it having to allocate more space later.
Using for..in fast enumeration syntax is more efficient than using array indexing, but for short arrays the difference is small. The code is also simpler to write and simpler to read, so I prefer that syntax where possible.
As Alex says, you could also create a category method on NSArray that would return a capitalized version of your array, or even a category on NSMutableArray that would replace the strings in the array "in place".
Works like charm.
NSString *myString = YOUR_ARRAY.uppercaseString;
[myNSMutableArray addObject:myString];
I want to make array of float type.
Anybody can help me?
NSArray *arrOfFloat = [[[NSArray alloc]initWithObjects:[12.2, 23.44], nil]];
But i want to make array dynamically.
But i want to make array dynamically.
This means you'll have to use an NSMutableArray.
NSMutableArray *array = [[NSMutableArray alloc] init];
[array addObject:#1.1];
[array addObject:#2.2];
...
You also can't add primitives to an array. You'll need to add objects. Notice the # I added before the numbers. This creates number literals.
If you have the floats you want to add as variables, you can auto boxing like this:
[array addObject:#(myFloatVariable)];
Use NSMutableArray class instead of a NSArray (this is a subclass of it), this way, within your code, you will be able to call :
NSMutableArray *yourArray = [NSMutableArray new];
[yourArray addObject:#(1.0f)];
NSArraycan only store objects, so in your case you would have to store your float as NSNumber. If you want to store objects dynamically, thus adding or removing them to an NSArray you have to use the mutable object type called NSMutableArray.
You'll need to wrap your float's in an NSNumber:
[NSNumber numberWithFloat:12.2];
If you're dynamically adding elements to an array, you need to use NSMutableArray.
NSMutableArray *array = [NSMutableArray array];
[array addObject:[NSNumber numberWithFloat:12.2]];
You can use NSMutableArray for example named arrOfFloat and add this :
[arrOfFloat addObject:[NSNumber numberWithFloat:3.5]];
[arrOfFloat addObject:[NSNumber numberWithFloat:23.44]];
Hope, It will may helpful to you.
Let's say I have an NSArray of NSDictionaries that is 10 elements long. I want to create a second NSArray with the values for a single key on each dictionary. The best way I can figure to do this is:
NSMutableArray *nameArray = [[NSMutableArray alloc] initWithCapacity:[array count]];
for (NSDictionary *p in array) {
[nameArray addObject:[p objectForKey:#"name"]];
}
self.my_new_array = array;
[array release];
[nameArray release];
}
But in theory, I should be able to get away with not using a mutable array and using a counter in conjunction with [nameArray addObjectAtIndex:count], because the new list should be exactly as long as the old list. Please note that I am NOT trying to filter for a subset of the original array, but make a new array with exactly the same number of elements, just with values dredged up from the some arbitrary attribute of each element in the array.
In python one could solve this problem like this:
new_list = [p['name'] for p in old_list]
or if you were a masochist, like this:
new_list = map(lambda p: p['name'], old_list)
Having to be slightly more explicit in objective-c makes me wonder if there is an accepted common way of handling these situations.
In this particular case Cocoa is not outdone in succinctness :)
NSArray *newArray = [array valueForKey:#"name"];
From the NSArray documentation:
valueForKey:
Returns an array containing the
results of invoking valueForKey: using
key on each of the receiver's objects.