NSArray adding elements

I have to create a dynamic NSArray, that is, I don't know the size of the array or what elements the array is going to have. The elements need to be added to the array dynamically. I looked at the NSArray class reference. There is a method called arrayWithObjects, which should be used at the time of initializing the array itself. But I don't know how to achieve what I need to do.

I need to do some thing like the following:

NSArray *stringArray = [[NSArray init] alloc] ;  
for (int i = 0; i < data.size; i++){  
    stringArray.at(i) = getData(i);
}