CPF Validator in swift

CPFValidator.swift

struct CPFValidator {
    
    var cpf: String
    // Based on:
    // https://pt.stackoverflow.com/questions/187106/valida%C3%A7%C3%A3o-cpf-e-cnpj
    func validate() -> Bool {
        let numbers = cpf.compactMap { (char) -> Int? in
           return Int(char)
        }
        guard numbers.count == 11 && Set(numbers).count != 1 else { return false }
        
        let sum1 = self.sum(slice: numbers[0..<9], initialValue: 10)
        let dv1 = sum1 > 9 ? 0 : sum1
        let sum2 = self.sum(slice: numbers[0..<10], initialValue: 11)
        let dv2 = sum2 > 9 ? 0 : sum2
        return dv1 == numbers[9] && dv2 == numbers[10]
    }    
    
    private func sum(slice: ArraySlice<Int>, initialValue: Int) -> Int {
        let enumSlice: EnumeratedSequence<ArraySlice<Int>> = slice.enumerated()
        let reduced = enumSlice.reduce(into: 0, { (acc, value) in
            acc+=(value.element * (initialValue-value.offset))
        })
        return 11 - (reduced % 11)
    }
}