Objective-C - How to implement an array of pointers in a method declaration

Question

Ok, if you take a look at my two previous posts (Link #2 in particular), I would like to ask an additional question pertaining to the same code. In a method declaration, I am wanting to define one of the parameters as a pointer to an array of pointers, which point to feat_data. I'm sort of at a loss of where to go and what to do except to put (NSMutableArray*)featDataArray in the declaration like below and access each object via another pointer of feat_data type. BTW, sorry to be asking so many questions. I can't find some of the things like this in the book I am using or maybe I'm looking in the wrong place?

-(void)someName:(NSMutableArray*)featDataArray;

feat_data *featDataPtr = [[feat_data alloc] init];
featDataPtr = [featDataArray objectAtIndex:0];

Link #1

Link #2

newacct · Accepted Answer · 2009-07-14 05:29:27Z

3

Your declaration looks fine. "NSMutableArray*" is an appropriate type for your parameter. (Objective-C doesn't have generics so you can't declare anything about what's inside the array.)

One problem I see in your code is that you allocate an object for no reason and then throw away the pointer (thus leaking memory).

I don't know what it is that you are trying to do, so here are some things that you can do with an NSMutableArray:

- (void)someName:(NSMutableArray *)featDataArray {

    feat_data *featDataPtr = [[feat_data alloc] init];
    [featDataArray addObject:featDataPtr]; // add an object to the end
    [featDataPtr release];

    feat_data *featDataPtr2 = [[feat_data alloc] init];
    [featDataArray replaceObjectAtIndex:0 withObject:featDataPtr2]; // replace an existing entry
    [featDataPtr2 release];

    feat_data *featDataPtr3 = [featDataArray objectAtIndex:0]; // get the element at a certain index
    // do stuff with featDataPtr3
}

answered Jul 14, 2009 at 5:29

newacct

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1 Comment

Josh Bradley Over a year ago

Ah ok, thanks. I didn't see what you were talking about for a second, but now I do.

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