How to filter a NSArray

Question

Hey i want to filter an NSArray. In this Array is a lot of information like name, town, telephonenumber, and so on. But some towns are twice or three times in the array.
I have property with a town in it.
So i want only those objects from the arry which match with the property.

For example: in the Array stands:

Frank, New York, 123456
Oliver, New York, 123456
Thomas, Boston, 123456

and when the property is New York i want olny objects 1 and 2.

Does anyone has an idea how i can do it?

This is my code:

NSString *filterString = newsArticle;
NSPredicate *prediacte = [NSPredicate predicateWithFormat:[NSString stringWithFormat:@"Ort == '%@'",filterString]];
newsTownArray = [news filteredArrayUsingPredicate:predicate];

and when i come to the line:

cell.textLabel.text=[[newsTownArray objectAtIndex:indexPath.row] objectForKey:"Name"];

possible duplicate of [filtering NSArray into a new NSArray in objective-c](http://stackoverflow.com/questions/110332/filtering-nsarray-into-a-new-nsarray-in-objective-c) — vikingosegundo, Jan 21 '13 at 13:13

Midhun MP · Accepted Answer · 2013-01-21T13:05:48.120

4

You need to use NSPredicate for this.

NSPredicate *predicate = [NSPredicate predicateWithFormat:@"town == 'New York'"];
[yourArray filterUsingPredicate:predicate];

Dynamically you can create predicate like:

NSPredicate *predicate = [NSPredicate predicateWithFormat:[NSString stringWithFormat:@"town == '%@'",yourInput]];

Here yourInput is a NSString which holds the required town name.

Please check these articles for more details:

edited Jan 21 '13 at 13:05

answered Jan 21 '13 at 12:58

Midhun MP

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but the town is not always the same. so is this also possible? – theandrew Jan 21 '13 at 13:02
@theandrew: I'll add dynamic query, just wait – Midhun MP Jan 21 '13 at 13:03
@theandrew: Please check now :) – Midhun MP Jan 21 '13 at 13:05
Thank you a lot :) But i also have to use the 2nd line from the first right? – theandrew Jan 21 '13 at 13:09
@theandrew: yes you need to use that line also – Midhun MP Jan 21 '13 at 13:39
i don't know why but it doesnt't work. i have all my objects in the array – theandrew Jan 23 '13 at 07:21
@theandrew: there should be any issues with your predicate – Midhun MP Jan 23 '13 at 08:20
The problem is the output. When i look at the content of the array it is ok. so I have only the objects with the right town. But i can't give it out. – theandrew Jan 23 '13 at 09:28
@theandrew: means ? I didn't get you, can you explain a little bit – Midhun MP Jan 23 '13 at 09:30
@theandrew: If that is the case then you need to reload the table and return the number of rows as the count of objects in `newsTownArray` array – Midhun MP Jan 23 '13 at 09:51
there is a delegate method called the `numberOfRowInSection` `return [newsTownArray count];` – Midhun MP Jan 23 '13 at 10:00
And you think that this is the failure? – theandrew Jan 23 '13 at 10:03
@theandrew: I think now you are returning some other values from there. Check that. – Midhun MP Jan 23 '13 at 10:07

Anoop Vaidya · Answer 2 · 2013-01-21T13:20:12.517

However you can do it within an array with the use of NSPredicate, but I will suggest to do bit differently, this will add up to your code and good programming way.

Create a custom class Person having these properties name, city and telephone.

Create an array that will store objects of Person.

After this you can manipulate/ filter / sort etc quite easily.

NSString *filterCity=@"Delhi";

NSMutableArray *yourArray=[NSMutableArray arrayWithArray:self.persons];
NSPredicate *predicate = [NSPredicate predicateWithFormat:[NSString stringWithFormat:@"city == '%@'",filterCity]];
[yourArray filterUsingPredicate:predicate];

NSLog(@"Filtered");
for (Person *per in yourArray) {
    NSLog(@"Name: %@, City: %@, Telephone: %@",per.name, per.city, per.telephone);

}

score 0 · Answer 3 · answered Jan 21 '13 at 13:03

Use this code

NSMutableArray *subpredicates = [NSMutableArray array];

    for(NSString *term in arryOfWordsToBeSearched) {
        NSPredicate *p = [NSPredicate predicateWithFormat:@"self contains[cd] %@",term];
        [subpredicates addObject:p];
        }

     NSPredicate *filter = [NSCompoundPredicate andPredicateWithSubpredicates:subpredicates];
    result = (NSMutableArray*)[arryOfDummyData filteredArrayUsingPredicate: filter];

How to filter a NSArray

3 Answers3