How to create a c array?

Question

How can I set a pointer to a C array in my constructor?

@implementation NSBufferedInputStream {
    char *buffer;
    int bufferSize;
}

- (id)initWithFileAtPath:(NSString *)path
{
    self = [super initWithFileAtPath:path];
    if (self) {
        bufferSize = 100;
        buffer = char[bufferSize]; // ERROR: Expected expression
    }
}
@end

From a quick glance, I'd say its because c doesn't support dynamic arrays without using malloc or something like that. — Daniel
– Daniel, Commented May 7, 2012 at 1:48

andyvn22 · Accepted Answer · 2012-05-07 01:50:59Z

1

If you truly need a dynamically-sized array,

- (id)initWithFileAtPath:(NSString *)path
{
    self = [super initWithFileAtPath:path];
    if (self) {
        bufferSize = 100;
        buffer = malloc(sizeof(char) * bufferSize);
    }
}

- (void)dealloc
{
    free(buffer);
    [super dealloc];
}

Otherwise, if your array size is known at compile time, just change your ivar from char *buffer; to:

char buffer[100]

answered May 7, 2012 at 1:50

andyvn22

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2 Comments

Stas Jaro Over a year ago

Why would you use dealloc if apple now has Automatic Reference Counting?

andyvn22 Over a year ago

ARC cannot handle the freeing of your malloc() calls for you--if you use malloc(), you must use free(). So implementing -dealloc here is important--but if you are using ARC, you should not call [super dealloc]; as that will be handled automatically.

MByD · Accepted Answer · 2012-05-07 01:48:55Z

0

If the size of the array is dynamic - use malloc, if not, you need to do it at the declaration:

@implementation NSBufferedInputStream {
    char buffer[100];
    int bufferSize;
}

answered May 7, 2012 at 1:48

MByD

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2 Comments

Stas Jaro Over a year ago

When you say dynamic, is it possible to increase the size of the array without copying its contents? That would be very useful. In this situation, I have a setBufferSize method in which I can change the buffer size before loading a file.

Stas Jaro Over a year ago

Would you know if NSMutableArray uses realloc? Currently I have a NSObject wrapper for my structs so I can use NSMutableArray and this is inefficient.

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