split.swift

let string = "Lorem ipsum dolor sit amet, consectetur adipiscing elit. Morbi enim lacus, ullamcorper in gravida a, semper id dolor. Mauris quis metus id"

extension String {
    func split(separator: Character, maxSplit: Int = .max, allowEmptySlices: Bool = false) -> [String] {
        return characters.split(separator, maxSplit: maxSplit, allowEmptySlices: allowEmptySlices).map(String.init)
    }
}

let words = try string.split(" ")
let counts = words.map { $0.characters.count }

print(counts)