Adding NSMutableDictionary to NSMutableArray

Question

NSMutableArray *arrData =[NSMutableArray array];
arrData =[data objectForKey:@"data"];
NSLog(@"%@",arrData);

NSLog will print like

data = 
(
   {
        date = "2016-01-20";
        "end_time" = "12:25:00";
        "start_time" = "11:00:00";
        "total_units" = 59;
    }
);

This data comes from server. Now, I want to add one more dictionary of data to this array coming from the server.

I did the following:

NSMutableDictionary *newDict = [NSMutableDictionary dictionary];
[newDict setObject:@"2016-01-22" forKey:@"date"];
[arrData addObject:newDict];

Now the app crashed. What went wrong?

[__NSArrayI addObject:]: unrecognized selector sent to instance 0x7fc4d3914d40

modified this line arrData =[[data objectForKey:@"data"]mutableCopy]; — kb920, Feb 04 '16 at 07:21
Make sure your array must be mutable. Try allocating your array like this `NSMutableArray *arrData = [[NSMutableArray alloc] init];` — Shehzad Ali, Feb 04 '16 at 07:24
OK so you aren't being quite straight here. You say `NSMutableArray *arrData =[NSMutableArray array];` but I expect you reassign `arrData` from a JSON parse, yes? — trojanfoe, Feb 04 '16 at 07:25

score 0 · Answer 1 · answered Feb 04 '16 at 07:21

0

NSMutableArray *arrData =[NSMutableArray array];

Is a method from NSArray class, which create an NSArray instance, not NSMutableArray instance.

What you need is, for example:

NSMutableArray *arrData =[NSMutableArray arrayWithCapacity:0];

Reference: https://developer.apple.com/library/mac/documentation/Cocoa/Reference/Foundation/Classes/NSArray_Class/index.html#//apple_ref/doc/uid/20000137-SW4

https://developer.apple.com/library/mac/documentation/Cocoa/Reference/Foundation/Classes/NSMutableArray_Class/#//apple_ref/doc/uid/20000138-SW1

answered Feb 04 '16 at 07:21

user2829759

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That's isn't true at all. – trojanfoe Feb 04 '16 at 07:23
I don't believe the OP has presented the question properly. I believe the `arrData` is later re-assigned with a non-mutable array. – trojanfoe Feb 04 '16 at 07:26

score 0 · Answer 2 · answered Feb 04 '16 at 07:26

0

NSMutableArray *arrData = [NSMutableArray arrayWithArray:[data objectForKey:@"data"]];

Use the above code instead. Your old code just move the pointer of arrData to [data objectForKey:@"data"]]. It access the same address

answered Feb 04 '16 at 07:26

Jonny Vu

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score 0 · Answer 3 · answered Feb 04 '16 at 07:27

0

for (NSDictionary *dict in [data objectForKey:@"data"])
{
    [arrData addObject:dict];
}

now you can add object whwnever you want to add in array

answered Feb 04 '16 at 07:27

Ashish Ramani

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score 0 · Answer 4 · answered Feb 04 '16 at 07:27

0

Use:

arrData = [data[@"data"] mutableCopy];

in order to create a mutable copy of the array.

answered Feb 04 '16 at 07:27

trojanfoe

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score 0 · Answer 5 · answered Feb 04 '16 at 07:32

Make sure your array must be mutable. Try allocating your array like this

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

Assign your response object to your arrData like this

NSMutableArray *arrData = [responseDictionary objectForKey:@"data"];

Then do your following stuff and also avoid using new keyword in the start of the variable name.

NSMutableDictionary *dict = [[NSMutableDictionary alloc] init];
                       [dict setObject:@"2016-01-22" forKey:@"date"];
                       [arrData addObject:dict];

score 0 · Answer 6 · answered Feb 04 '16 at 07:33

You are assigning an NSDictionary object reference to an NSMutableArray object.

arrData =[data objectForKey:@"data"];

Then, when you try to execute addObject method on arrData it crashes because addObject method does not exist for an NSDictionary object.

use :

[arrData addObject:[data objectForKey:@"data"]]

Adding NSMutableDictionary to NSMutableArray

6 Answers6