How to declare class array in objective c

Question

I can declare NSMutableArray or NSArray but I want to declare class array. Let say user is a class so I can declare array as:

user* obj[10];

it is valid in Objective c, but I am not sure how I can set array capacity dynamically. Which we usually do with MutableArray as initWithCapacity:..

This is what I am doing with class:

user* objuser;
CustomOutput* output = [[CustomOutput alloc] init];
[objuser cutomSerialize:output];
NSMutableData* data = output.data;

But If I have array as:

NSMutableArray* aryUserObj;

I can't call cutomSerialize method from arryUserObj.

I want to Serialize all the userObj at ones and get a single NSData object.

This has nothing to do with "declaring a class array" (whatever that means) — it has to do with the fact that you need some way to serialize several objects objects together, which would have to be part of the class's implementation, either by allowing the serialization method to build up the serialized data gradually or by giving the class a method that takes an array of instances and uses its serialization logic to do them all at once. — Chuck
– Chuck, Commented Oct 11, 2010 at 20:57

Yuji · Accepted Answer · 2010-10-11 22:29:12Z

4

The standard approach to serialize an array of objects is for you to define encodeWithCoder: and initWithCoder: in your User object:

@interface User: NSObject {
 ....
}
-(void)encodeWithCoder:(NSCoder*)coder ;
-(id)initWithCoder:(NSCoder*)coder;
@end

What you currently have in CustomSerialize should be in these methods.

Then, if you want to encode an object, you do

User* user=... ;
NSData* data=[NSKeyedArchiver archivedDataWithRootObject:user];

and decode it:

User* user=[NSKeyedUnarchiver unarchiveObjectWithData:data];

If you have an array of objects,

NSMutableArray* array=... ; // an array of users
NSData* data=[NSKeyedArchiver archivedDataWithRootObject:array];

and

NSArray* array=[NSKeyedUnarchiver unarchiveObjectWithData:data];

Iteration over array is done automatically. Note also that you don't get the mutable array back, it's an immutable array.

edited Oct 11, 2010 at 22:29

answered Oct 11, 2010 at 18:49

Yuji

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1 Comment

Dave DeLong Over a year ago

+1, except that NSKeyedUnarchiver does not maintain the mutability of the objects. IOW, if you archive an NSMutableArray, you're going to get an NSArray back. It's kind of lame, but that's how it goes.

Dave DeLong · Accepted Answer · 2010-10-11 16:37:50Z

2

NSMutableArray * users = [NSMutableArray array];
for (int i = 0; i < someNumber; ++i) {
  User * aUser = [[User alloc] initWithStuff:someStuff];
  [users addObject:aUser];
  [aUser release];
}

answered Oct 11, 2010 at 16:37

Dave DeLong

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4 Comments

iPhoneDev Over a year ago

I know this... but I don't want to use NSMutableArray need to use only class array. Because I have to serialize this class object and I can assess serialize method only in class not from MutableArray. Ex: obj.serialize(data); This could possible only if I have class obj.

Dave DeLong Over a year ago

@iPhoneDev you can still iterate the objects in the array and serialize them, or you can implement the <NSCoding> protocol, then just serialize all of the objects at once by serializing the array.

iPhoneDev Over a year ago

Yes this I want to serialize all object at ones and send it as NSData. Please let me know how we can use NSCoding for this..

Dave DeLong Over a year ago

@iPhoneDev read the documentation on Archiving and Serializations and let us know what questions you have: developer.apple.com/library/ios/#documentation/cocoa/Conceptual/…

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