CODEWITHSUNDEEP
objective-carrays
coiler90
coiler90

Reputation: 53

How to make an array by jumping over every 1 index

Hi is there a way to make an array by jumping over every 1 index like lets say i have an array with objects like this: 

NSArray *array =[NSArray alloc] initWithObjects:@"id",@"name",@"id",@"name",@"id",@"name"..

... and so on, can i make an array by taking only the ID objects and/or NAMES. I'm stuck in this, what i really want to achieve is i want id's to be in the tableview subtitle, and names on tableview title. any suggestions?

EDIT: Thanks you for your help everybody, already got my answer, i couldn't go though NSDictionary because, i'm getting objects from .php. Anyways thank you!

Upvotes: 0

Views: 363

Answers (5)

CRD
CRD

Reputation: 53010

Many answers will just suggest using some other data structure which is recommended if you can. But assuming you have such an array and need to do this its not hard. You could process the array into two - potentially a lot of copying; or you could simply take a view of the array - which trades a smidgin in access time for copying. Here is JASArray with absolutely no checking code (that is left to you):

@interface JASArray : NSArray

- (id) initWith:(NSArray *)baseArray jumpTo:(NSUInteger)jumpTo strideBy:(NSUInteger)strideBy;

@end

To override NSArray you only need to implement count and objectAtIndex::

@implementation JASArray
{
   NSUInteger jump;
   NSUInteger stride;
   NSArray *base;
}

- (id) initWith:(NSArray *)baseArray jumpTo:(NSUInteger)jumpTo strideBy:(NSUInteger)strideBy
{
   self = [super init];
   if (self)
   {
      base = baseArray;
      jump = jumpTo;
      stride = strideBy;
   }
   return self;
}

- (NSUInteger) count
{
   return 1 + (base.count - jump - 1) / stride;
}

- (id) objectAtIndex:(NSUInteger)index
{
   return [base objectAtIndex:(jump + index * stride)];
}

@end

Now a test, note the on purpose mismatch pairs as a test:

NSArray *array =@[ @"id1", @"name1", @"id2", @"name2", @"id3", @"name3", @"id4" ];
JASArray *ids = [[JASArray alloc] initWith:array jumpTo:0 strideBy:2];
JASArray *names = [[JASArray alloc] initWith:array jumpTo:1 strideBy:2];
NSLog(@"%@\n%@\n%@", array, ids, names);

Output:

JumpAndStride[10480:303] (
    id1,
    name1,
    id2,
    name2,
    id3,
    name3,
    id4
)
(
    id1,
    id2,
    id3,
    id4
)
(
    name1,
    name2,
    name3
)

HTH

Upvotes: -1

ssantos
ssantos

Reputation: 16536

If you want ids and names separated in two different arrays, you could iterate through the original array, and use mod operator like this.-

NSArray *array = [[NSArray alloc] initWithObjects:@"id",@"name",@"id",@"name",@"id",@"name", nil];
NSMutableArray *ids = [[NSMutableArray alloc] init];
NSMutableArray *names = [[NSMutableArray alloc] init];

for (int i = 0; i < array.count; i ++) {
    if (i % 2 == 0) {
        [ids addObject:[array objectAtIndex:i]];
    } else {
        [names addObject:[array objectAtIndex:i]];
    }
}

Upvotes: 1

Anupdas
Anupdas

Reputation: 10201

You can easily achieve by making an array of dictionary objects.

NSArray *array = @[@{@"Id":1, @"Name":@"UserName1"},@"Id":2, @"Name":@"UserName2"}];

And in the cellForRowAtIndexPath: method

NSDictionary *user = self.array[indexPath.row];

cell.textLabel.text = user[@"Id"];
cell.detailLabel.text = user[@"Name"];

Upvotes: 2

Gabriele Petronella
Gabriele Petronella

Reputation: 108159

You have two options

First (naive) one:

cell.subtitle.text = array[indexPath.row*2];
cell.title.text = array[indexPath.row*2+1];

Anyway, a more correct alternative would be to use an array of NSDictionarys

NSArray *array = [NSArray alloc] initWithObjects:@{
    @"id": @"theId", @"name" : @"theName"},
    @"id": @"anotherId", @"name" : @"anotherName"},
    ...];

And then

cell.subtitle.text = array[indexPath.row][@"id"];
cell.title.text = array[indexPath.row][@"name"];

Upvotes: 2

Andrew
Andrew

Reputation: 7719

Why not use 2 arrays from the start? If you have to split the arrays, an easy way would be to do it on even and odd numbers.

NSArray *array =[[NSArray alloc] initWithObjects:@"id",@"name",@"id",@"name",@"id",@"name",nil];

NSArray *ids = [array objectsAtIndexes:[array indexesOfObjectsPassingTest:^BOOL(id obj, NSUInteger idx, BOOL *stop) {
    return ((idx % 2) == 0);
}]];

NSArray *names = [array objectsAtIndexes:[array indexesOfObjectsPassingTest:^BOOL(id obj, NSUInteger idx, BOOL *stop) {
    return ((idx % 2) != 0);
}]];

Upvotes: 1

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