将NSArray传递给cpp函数

Question

I need to call a cpp function like

void myFunc(float **array2D, int rows, int cols)
{
}

within an objective-c object. Basically, the array is created in my objective-c code as I create an NSArray object. Now, the problem is how to pass this array to my cpp function.

I am a bit new to these mixed c++/objective-c stuffs so any hint will be highly appreciated.

Thanks

Answer 1

I guess you have to convert the NSArray to a plain C array. Something like:

NSArray *myNSArray; // your NSArray

int count = [myNSArray count];
float *array = new float[count];
for(int i=0; i<count; i++) {
    array[i] = [[myNSArray objectAtIndex:i] floatValue];
}

or, as a commenter suggested (assuming your NSArray contains NSNumber s):

NSArray *myNSArray; // your NSArray

int count = [myNSArray count];
float *array = new float[count];
int i = 0;
for(NSNumber *number in myNSArray) {
    array[i++] = [number floatValue];
}

Answer 2

Look at this post .

Check out the answer that mentions using [NSArray getObjects] to create a c-style array.

Here's the code that the poster put in there:

NSArray *someArray = /* .... */;
NSRange copyRange = NSMakeRange(0, [someArray count]);
id *cArray = malloc(sizeof(id *) * copyRange.length);

[someArray getObjects:cArray range:copyRange];

/* use cArray somewhere */

free(cArray);

Answer 3

Alternately, since CFArray is toll-free bridged to NSArray, could you call those C functions from your C++ function? I'd look around, wouldn't be surprised if there weren't a C++ wrapper to give similar semantics, or one could be written easily enough.