nsarray

Can someone please show me the code for sorting an NSMutableArray? I have the following NSMutableArray: NSMutableArray *arr = [[NSMutableArray alloc] init]; with elements such as "2", "4", "5", "1", "9", etc which are all NSString. I'd like to sort the list in descending order so that the largest valued integer is highest in the list (index 0). I tried the following: [arr sortUsingSelector:@selector(compare:)]; but it did not seem to sort my values properly. Can someone show me code for properly doing what I am trying to accomplish? Thanks! It's pretty simple to write your own comparison

I have a database model class that is a NSObject . I have a set of these objects in a NSMutableArray . I use indexOfObject: to find a match. Problem is the model object's memory address changes. So I am overriding the hash method to return the model's row ID. This however does not fix it. I also have to override the isEqual: method to compare the value of the hash method. What does the isEqual: method use to determine equality by default? I'm assuming it uses the memory address. After reading the isEqual: documentation I thought it used the value from the hash method. Obviously, that is not

I have an NSArray of CalEvents returned with the [CalCalendarStore eventPredicateWithStartDate] method. From the events returned, I am trying to keep only those in which the title of the event == @"on call" (case-insensitive). I am able to keep in the array those events whose title includes @"on call" with the following code (where 'events' is a 'NSArray' populated with CalEvents ): NSPredicate *onCallPredicate = [NSPredicate predicateWithFormat:@"(SELF.title CONTAINS[c] 'on call')"]; [events filteredArrayUsingPredicate:onCallPredicate]; I've tried using a predicate format string like: @"SELF

I have an array of dictionaries. I would like to extract an array with all the elements of one particular key of the dictionaries in the original array. Can this be done without enumeration? Yes, use the NSArray -valueForKey: method. NSArray *extracted = [sourceArray valueForKey:@"a key"]; Yes, just use Key-Value Coding to ask for the values of the key: NSArray* names = [NSArray arrayWithObjects: [NSDictionary dictionaryWithObjectsAndKeys: @"Joe",@"firstname", @"Bloggs",@"surname", nil], [NSDictionary dictionaryWithObjectsAndKeys: @"Simon",@"firstname", @"Templar",@"surname", nil],

How to convert NSArray into NSString in objective-c? Bearing in mind that you don't say what's in the NSArray, you can do this: NSArray *arr = [NSArray arrayWithObjects: @"foo", @"bar", @"baz"]; [arr componentsJoinedByString: @","] Aternatively to Frank's method, which works pretty well, you could also do NSString *myArrayString = [array description]; The default implementation of description on NSArray will print out the contents in a neatly formatted fashion. TheGreen This is how I have converted my NSArray to NSString NSError *error = nil; NSData *data = [NSJSONSerialization

Let's say I have an NSArray of NSNumbers like this: 1, 2, 3 Then the set of all possible permutations would look something like this: 1, 2, 3 1, 3, 2 2, 1, 3 2, 3, 1 3, 1, 2 3, 2, 1 What's a good way to do this in objective-c? I have used the code from Wevah's answer above and discovered some problems with it so here my changes to get it to work properly: NSArray+Permutation.h @interface NSArray(Permutation) - (NSArray *)allPermutations; @end NSArray+Permutation.m #import "NSArray+Permutation.h" #define MAX_PERMUTATION_COUNT 20000 NSInteger *pc_next_permutation(NSInteger *perm, const NSInteger