Replace content of NSMutableArray with NSArray

Question

I'm working on an app that needs to retrieve some data from a server. I have created a "Server" class which handles all the communication and has a NSMutableArray *sessionData variable where I would like to store the data coming from the server (btw, is this approach correct?).

I have the data in an NSArray. I would like the NSMutableArray to have the same content of the NSArray but I didn't find any way to do this (sessionData = requestResult).

(subquestion: do I have to initialize in some way the NSMutableArray before using ? I have only declared it with @property and @synthesize)

I have tried this but didnt work: [sessionData removeAllObjects]; [sessionData setArray:result]; — Antonio Madonna
– Antonio Madonna, Commented Mar 30, 2012 at 12:44

Sergey Kalinichenko · Accepted Answer · 2012-03-30 12:47:26Z

5

The code you tried (from the comment) should have worked. The reason it did not work is that your sessionData was nil.

You need to initialize your sessionData - set it to [NSMutableArray array] in the initializer; then your code

[sessionData removeAllObjects];
[sessionData setArray:result];

will work perfectly. You do not even need the first line - the second one replaces the content of sessionData with that of the result.

answered Mar 30, 2012 at 12:47

Sergey Kalinichenko

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2 Comments

Antonio Madonna Over a year ago

Thank you. Is this code good to initialize it (from the the init method of my class) ? self->sessionData = [[NSMutableArray alloc] init];

Sergey Kalinichenko Over a year ago

@anthmad Yes, this initialization code should work. If you are not on ARC, consider assigning to a property, rather than to its backing ivar; if you're on ARC, it does not matter.

Alexander · Accepted Answer · 2012-03-30 12:46:04Z

4

Try this way:

sessionData = [result mutableCopy];
[result release];

Or

NSMutableArray *sessionData = [[NSMutableArray alloc] initWithContentsOfArray:result];

answered Mar 30, 2012 at 12:46

Alexander

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Comments

user1040049 · Accepted Answer · 2012-03-30 12:49:06Z

0

Or, if you could do this:

NSMutableArray *session = [NSMutableArray arrayWithArray:someArray];

answered Mar 30, 2012 at 12:49

user1040049

Comments

Himanshu A Jadav · Accepted Answer · 2012-03-30 13:02:11Z

0

1. is this approach correct?

Yes.

2. I didn't find any way to do this (sessionData = requestResult)

As many have suggested you can use mutableCopy to assign requestResult to sessionData OR you can use arrayWithArray as one answer suggests.

3. do I have to initialize in some way the NSMutableArray before using ?

Yes. If you are changing any variable it must have memory allocated.

answered Mar 30, 2012 at 13:02

Himanshu A Jadav

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Comments

h4cky · Accepted Answer · 2012-03-30 13:11:10Z

0

In your example something like this:

NSArray *requestData = [[NSArray alloc] initWithObjects:@"3", @"4", @"5", nil];
_sessionData = [[NSMutableArray alloc] initWithArray:requestData];
[requestData release];

NSLog(@"%@", [sessionData objectAtIndex:0]); // 2012-03-30 15:53:39.446 <app name>[597:f803] 3
NSLog(@"count: %d", [sessionData count]); //2012-03-30 15:53:39.449 <app name>[597:f803] count: 3

edited Mar 30, 2012 at 13:11

answered Mar 30, 2012 at 12:58

h4cky

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1 Comment

Antonio Madonna Over a year ago

sessionData is a property that I need to access from other methods. Your code will create a local mutable array ?

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