NSMutableArray of Structures?

Question

How can I create NSMutableArray of Structures?

I can create an array of Structures in standard-c but am running into problems in objective-c.

standard-c:

struct person people[10];

thanks

I have seen a lot of your questions come up in the last 2 days or so, and it seems like they all have to do with kinda fighting the Objective-C way, and OOP in general.. the collection classes are your friends, people should be a class call People and it should be added to an NSArray or NSMutableArray. It will be so much easier to get memory management right. — Grady Player
– Grady Player, Commented Jul 13, 2011 at 20:18
I'd take it one step further; Don't use a structure at all. There is no reason why your person can't be a class Person (at least no reason as indicated by your questions so far). You are going down a path that is a complete waste of time, it seems. — bbum
– bbum, Commented Jul 13, 2011 at 20:58

benzado · Accepted Answer · 2011-07-13 20:10:58Z

3

You need to copy each struct into an NSData or NSValue object in order to place it in an NSArray.

// in
struct person someGuy = ...;
NSData *personData = [NSData dataWithBytes:&someGuy length:sizeof(struct person)];
[personArray addObject:personData];

// out
NSData *personData = [personArray objectAtIndex:whatever];
struct person someGuy;
[personData getBytes:&someGuy];

You should understand the difference between stack and heap and how to work with pointers (or be ready to learn), otherwise you will see a lot of EXC_BAD_ACCESS (or worse, no exceptions, just mysterious garbage data).

edited Jul 13, 2011 at 20:10

answered Jul 13, 2011 at 20:05

benzado

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4 Comments

Kristen Martinson Over a year ago

Since it looks lot a lot of work to do Objective-c method for array of structures... is there any reason why I should not just implement standard-c convention for the structure or do I run the risk of the app crashing?

benzado Over a year ago

It's impossible to answer that without knowing more about your use case. But in general, I'd say don't mess with C structs unless you need them to interface with a C library that uses them.

benzado Over a year ago

@Suran STL containers are not available unless you are using Objective-C++, which you shouldn't be using unless you need to link your code with existing C++ code.

Suran Over a year ago

@benzado You're right..:-) But, in my case it was useful, and from a performance point of view, I think, in this case, using STL containers will be better...

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