build an NSArray from nsarray already exist

Question

i have an NSArray with JsonValue from my webservice.

myArray = [responseString JSONValue];

this Array give me that in a NSLog:

 2012-02-18 18:22:46.338 Test[2758:fb03] myArray: (
            {
            receiver = david;
            sender = sophie;
            message = "test1";
            photo = "****************.jpg";
        },
            {
            receiver = david;
            sender = matt;
            message = "test2";
            photo = "****************.jpg";
        },
            {
            receiver = sophie;
            sender = mike;
            message = "test1";
            photo = "****************.jpg";
        },
            {
            receiver = david;
            sender = ali;
            message = "test1";
            photo = "****************.jpg";
        },
            {
            receiver = mike;
            sender = david;
            message = "test1";
            photo = "****************.jpg";
        },
            {
            receiver = admin;
            sender = david;
            message = "test1";
            photo = "****************.jpg";
        }
    )

I need to create a new array with only sender = 'David'

i try with that:

for(int i=0;i<[myArray count];i++)
   {
    NSDictionary *dict1=[myArray objectAtIndex:i];


       if ( [[dict1 objectForKey:@"sender"] isEqualToString:@"david"]) 


       {

           NSLog(@"YES");


           myNewArray = [[NSArray alloc] initWithObjects:dict1, nil];

            NSLog(@"array %@",myNewArray);
            NSLog(@"count %d",[myNewArray count]);



       }
       else
       {
           NSLog(@"NO");


           myNewArray2 = [[NSArray alloc] initWithObjects:dict1, nil];

            NSLog(@"array2 %@",myNewArray2);
            NSLog(@"count2 %d",[myNewArray2 count]);
       }
   }

this myNewArray give me that:

           2012-02-18 18:22:46.341 Test[2758:fb03] myNewArray (
        {
            receiver = mike;
            sender = david;
            message = "test1";
            photo = "****************.jpg";
    }
)
          2012-02-18 18:22:46.341 Test[2758:fb03] myNewArray (
        {
            receiver = admin;
            sender = david;
            message = "test1";
            photo = "****************.jpg";
    }
)

But i need to have a array like that:

2012-02-18 18:22:46.338 Test[2758:fb03] myNewArray: (

        {
            receiver = mike;
            sender = david;
            message = "test1";
            photo = "****************.jpg";
    },
        {
            receiver = admin;
            sender = david;
            message = "test1";
            photo = "****************.jpg";
    }
)

thx for reading

Answer 1

There's a much easier way. Try using NSArray's filteredArrayUsingPredicate: where the predicate in your case is something like this:

NSString *attribute = @"sender";
NSString *senderFilter = @"david";
NSPredicate *predicate = [NSPredicate predicateWithFormat:@"%K like %@", attribute, senderFilter];

NSArray *filteredArray = [array filteredArrayUsingPredicate:predicate];

For more details on predicates, try the Predicate Programming Guide.

Answer 2

Declare myNewArray outside of the cycle, and make it a NSMutableArray (it'll allow to add new objects )

myNewArray = [[NSMutableArray alloc] array];
for(int i=0;i<[myArray count];i++)
{
    ...
}

then add object to this array if some condition is equal

NSLog(@"YES");
[myNewArray addObject:dict1];

Answer 3

A NSArray is immutable, you will need a NSMutableArray. And you are re-initliazing the new array on every loop, which you cannot do if you want to keep the previous values.

NSMutableArray *a = [[NSMutableArray alloc] init];

for (int i = 0; i < [myArray count]; i++) {
    NSDictionary *m = [myArray objectAtIndex:i];

    if ([[m objectForKey:@"sender"] isEqualToString:@"david"]) {
        [a addObject:m];
    }
    ...
}