Removing matching elements from a collection: removeAll(where:)

Swift version: 5.10

Paul Hudson @twostraws May 28th 2019

The removeAll(where:) method performs a high-performance, in-place filter for collections. You give it a closure condition to run, and it will strip out all objects that match your condition.

For example, if you have a collection of names and want to remove people called “Terry”, you’d use this:

var pythons = ["John", "Michael", "Graham", "Terry", "Eric", "Terry"]
pythons.removeAll { $0 == "Terry" }
print(pythons)

Using removeAll(where:) is more readable than using a reversed filter() call because it specifies what you don’t want rather than what you want. It’s also more performant than filter() because it removes object in place, and so avoids extra copying.