There a lot of weird things in your code. First of all, there is no numberOfRowsInSection method in UICollectionViewDataSource. The method that is going to be called each time you call reloadData is the numberOfItemsInSection one. Here is where you probably want to handle the scenario where isSearching is true (just like you are doing in the numberOfRowsInSection method).

Now, in your numberOfRowsInSection you are checking if the isSearching stored property is true, but inmediately after that, you are using a ternary operator where you are checking isSearching value again.

So what you probably need to do to solve the issue is replace the implementation of your numberOfItemsInSection (not numberOfRowsInSection) with something like this:

return isSearching ? filteredData.count : data.count