Objective C - Can't change value in NSMutableArray

Question

I can retrieve data I need from API, but then I can't change values of NSMutableArray. Here's the data I get from API:

{
favorites =     (
            {
        id = 766;
        imageUrl = "766.jpg";
        name = "Ground Beef 93% Lean 1LB PKG";
        price = "5.99";
        qty = 5;
        sale = "<null>";
        switch = 1;
    },
            {
        id = 3270;
        imageUrl = "3270.jpg";
        name = "Arnold Premium Italian Bread 20oz PKG";
        price = "5.39";
        qty = 5;
        sale = "<null>";
        switch = 1;
    },...
);
success = true;
}

I declare favorites property in the interface part :

@property (nonatomic, retain) NSMutableArray *favorites;

I store the data in NSMutableArray like this :

NSError *myError = nil;
NSMutableArray *response = [[NSJSONSerialization JSONObjectWithData:self.responseData options:NSJSONReadingMutableLeaves error:&myError] mutableCopy];

Then I store favorite products in another NSMutableArray object :

NSString *success = [response valueForKey:@"success"];
if([success isEqualToString:@"true"]) {
    self.favorites = [response valueForKey:@"favorites"];
}

With this data I can display all images, prices, etc. in the table. Problem is when I want to update values in self.favorites mutable array:

[self.favorites[indexPath.row] setObject:@"0" forKey:@"switch"];

I get this error : -[__NSCFDictionary setObject:forKey:]: mutating method sent to immutable object. I even tried to add mutableCopy when assigning array to favorites :

self.favorites = [[response valueForKey:@"favorites"] mutableCopy];

but that did not work either.

Your array is mutable, but the dictionaries it contains are still immutable. — godel9
– godel9, Commented Jul 6, 2014 at 17:12
Like @rmaddy said. I need NSJSONReadingMutableContainers, that's what makes the dictionaries mutable. — ivanharmat
– ivanharmat, Commented Jul 6, 2014 at 17:35

rmaddy · Accepted Answer · 2014-07-06 17:24:19Z

1

You want NSJSONReadingMutableContainers, not NSJSONReadingMutableLeaves.

Using NSJSONReadingMutableLeaves gives you mutable strings and other mutable objects inside the containers. Not what you need here.

answered Jul 6, 2014 at 17:24

rmaddy

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