CODEWITHSUNDEEP
iosobjective-ccarraysdeep-copy
K.He
K.He

Reputation: 137

Deep copy of object with C array

I have an object with a 2d C array (can't figure out how to do the same with NSArray) and I also need this object to provide deep copies of itself. I'm trying to implement the NSCopying protocol except when trying to make a copy of the c array i can't figure out how to reference self's array and the copy's array. Since it's not a property and obj c doesn't support c array properties as far as i know, i don't know how to set the new copy's array.

I've tried typedefing my array as a struct but I'm also using ARC so that isn't a valid solution

Hopefully I'm not missing something basic. Thanks.

Upvotes: 0

Views: 205

Answers (1)

user3386109
user3386109

Reputation: 34829

You can use the -> notation to access the instance variables of the copied object. When making a deep copy, each object in the array must be copied. 

// define a custom class to store in the array
@interface OtherClass : NSObject <NSCopying>
@property (nonatomic, strong) NSString *string;
@end

@implementation OtherClass
- (id)copyWithZone:(NSZone *)zone
{
    OtherClass *temp = [OtherClass new];
    temp.string = [self.string stringByAppendingString:@" (copy)"];
    return( temp );
}

- (void)dealloc
{
    NSLog( @"OtherClass dealloc: %@", self.string );
}
@end

// define the class that contains a C array of custom objects
@interface SomeClass : NSObject <NSCopying>
{
    OtherClass *array[5][5];
}
@end

@implementation SomeClass
- (id)copyWithZone:(NSZone *)zone
{
    SomeClass *temp = [SomeClass new];

    for ( int i = 0; i < 5; i++ )
        for ( int j = 0; j < 5; j++ )
            temp->array[i][j] = [array[i][j] copy];

    return( temp );
}

- (void)storeObject:(OtherClass *)object atRow:(int)row Col:(int)col
{
    array[row][col] = object;
    object.string = [NSString stringWithFormat:@"row:%d col:%d", row, col];
}

- (void)dealloc
{
    NSLog( @"SomeClass dealloc" );
}
@end

// test code to create, copy, and destroy the objects
@implementation ViewController

- (void)viewDidLoad
{
    [super viewDidLoad];

    SomeClass *a = [SomeClass new];

    for ( int i = 0; i < 5; i++ )
        for ( int j = 0; j < 5; j++ )
            [a storeObject:[OtherClass new] atRow:i Col:j];

    SomeClass *b = [a copy];

    NSLog( @"Releasing A" );
    a = nil;

    NSLog( @"Releasing B" );
    b = nil;
}

Upvotes: 2

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