Returning multiple non-Objective C objects/variables from method

Question

I know NSDictionary can be used to return multiple things from a method when all the objects are Objective C type objects, but is there a way to package objects that are non-Objective C?

I have a method that I need to return an int and an IplImage. Without converting the IplImage to a NSValue (which I do not know how to do and wish to avoid), can I return 2 items from a method?

Also note that this method is defined in a separate class from which it is being called, thus I don't think I can use a class variable to store the int (or maybe I can?).

Thanks.

justin · Accepted Answer · 2011-10-17 19:29:48Z

1

this approach will work for simple cases, i am sure you have seen it:

- (BOOL)caclulate:(NSError**)outError;

it returns a BOOL and an NSError.

To return an int:

- (BOOL)caclulate:(int*)outInt;

Using that approach, you can declare your method like this:

- (int)calculate:(IplImage*)outImage;

and then the caller's code takes the following form:

IplImage outImage;
int result = [object calculate:&outImage];

edited Oct 17, 2011 at 19:29

answered Oct 17, 2011 at 18:12

justin

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1 Comment

Kevin_TA Over a year ago

I'm not sure I understand, so where is the IplImage returned?

ayoy · Accepted Answer · 2011-10-17 18:17:57Z

1

If NSError** solution doesn't work for you, you might want to create a helper struct that holds both the int and IplImage:

typedef struct _Data {
    int num;
    IplImage image;
} Data;

and then pass it around.

answered Oct 17, 2011 at 18:17

ayoy

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cocoahero · Accepted Answer · 2011-10-17 18:14:20Z

0

Short answer: no.

The common way is what you described, using a NSDictionary. Unfortunately, that means working with NSValue for non-standard types (NSNumber, etc).

Or you could use in/out params similar to the way most methods work with NSError.

answered Oct 17, 2011 at 18:14

cocoahero

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