NSMutableArray always converting to NSArray

Question

I have an NSMutableArray that did its initialisation like follows:

@interface Countries ()
{
    NSMutableArray *arrayofCountry;
}
@end


- (void)viewDidLoad
{
       //...
       arrayofCountry=[[NSMutableArray alloc]init];
       //...
}

Then I wanted to apply a removeObjectAtIndex to that NSMutableArray:

[arrayofCountry removeObjectAtIndex:sourceRow];

The problem is it is crashing with that log:

-[__NSArrayI removeObjectAtIndex:]: unrecognized selector sent to instance

I verified it with:

NSLog( NSStringFromClass( [arrayofCountry class] ));

and it's returning __NSArrayI. The question is how it was converted to NSArray? I'm just populating it with:

arrayofCountry=[JSON valueForKeyPath:@"country_name"];

Thank you for your help.

The problem lies in your last code bit. arrayOfCountry = [JSON valueForKeyPath:@"country_name"]; does NOT populate it. It replaces it. — Rey Gonzales
– Rey Gonzales, Commented Jul 18, 2013 at 14:46

Alladinian · Accepted Answer · 2013-07-18 14:35:20Z

4

Try this. This will create a new NSMutableArray based on the contents of your other array.

arrayofCountry = [NSMutableArray arrayWithArray:[JSON valueForKeyPath:@"country_name"]];

edited Jul 18, 2013 at 14:35

Alladinian

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answered Jul 18, 2013 at 14:32

Mark McCorkle

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1 Comment

acorc Over a year ago

If you need a retained version you can do the same thing with [[NSMutablArray alloc] initWithArray: ]; If DCGoD's answer is correct, please mark it as such.

Sam Spencer · Accepted Answer · 2013-07-18 14:42:12Z

2

If the value stored in the JSON file with the key country_name is an NSArray then it can't be copied into an NSMutableArray without changing it. Try doing this:

arrayofCountry = [[JSON valueForKeyPath:@"country_name"] mutableCopy];

Also, when creating your NSMutableArray create it like this (instead of using alloc and then init):

arrayOfCountry = [NSMutableArray array];

edited Jul 18, 2013 at 14:42

answered Jul 18, 2013 at 14:33

Sam Spencer

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3 Comments

androniennn Over a year ago

It worked too. So the problem is that I was getting an array from the JSON and applying it to an NSMutableArray.

Sam Spencer Over a year ago

@androniennn Correct! And that's why you were getting a crash, and the change in pointer type. Accept the answer that best resolves the problem and explains it. :-)

Desdenova Over a year ago

@androniennn Even though you overwrite later on, every other answer is missing this technically important bit arrayOfCountry = [NSMutableArray array];

Balu · Accepted Answer · 2013-07-18 14:34:24Z

1

try like this,

arrayofCountry=(NSMutableArray *)[JSON valueForKeyPath:@"country_name"];

as @ Ahmed Mohammed:suggested try like this way

arrayofCountry=[[JSON valueForKeyPath:@"country_name"] mutableCopy];

edited Jul 18, 2013 at 14:34

answered Jul 18, 2013 at 14:27

Balu

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3 Comments

androniennn Over a year ago

tried it right now and it's always crashing at removeObjectAtIndex.

Balu Over a year ago

are you getting same crash description?

Ahmed Mohammed Over a year ago

casting the pointer does not change the underlying object's class!! Instead you should try arrayofCountry=[[JSON valueForKeyPath:@"country_name"] mutableCopy];

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