Question

I have an NSMutableArray that will start with 0 objects in it, but as the program progresses objects will be added to it. How can I shift all elements down, when a new element is added?

For example:

1) NSMutableArray array = 0 elements

2) NSMutableArray array = 1 element { [0,a]}

3) NSMutableArray array = 2 elements {[0, b], [1,a]}

4) NSMutableArray array = 3 elements {[0,c],[1,b],[2,c]}

As can be seen through the above list as objects are added to the array, all current elements move down. However, I do not want my array to exceed a certain size (lets say 10 elements). When a element is pushed to 11 I want it “pushed” out of the array. How can I go about doing this?

Similar questions: NSMutablearray move object from index to index

Answer 1

You can do that like this:

[array insertObject:object atIndex:0];
if ([array count] > 10) {
    [array removeLastObject];
}

The first line will automatically push the other elements out of the way, and the next bit just makes sure the array’s length never exceeds 10.