neoneye neoneye - 2 months ago 7
Ruby Question

Swift equivalent of Ruby's "each_cons"

Ruby



Ruby has each_cons that can be used like this

class Pair
def initialize(left, right)
@left = left
@right = right
end
end
votes = ["a", "b", "c", "d"]
pairs = votes.each_cons(2).map { |vote| Pair.new(*vote) }
p pairs
# [#<Pair @left="a", @right="b">, #<Pair @left="b", @right="c">, #<Pair @left="c", @right="d">]


Swift



The same code in swift, but without the
each_cons
function

struct Pair {
let left: String
let right: String
}
let votes = ["a", "b", "c", "d"]
var pairs = [Pair]()
for i in 1..<votes.count {
let left = votes[i-1]
let right = votes[i]
pairs.append(Pair(left: left, right: right))
}
print(pairs)
// [Pair(left: "a", right: "b"), Pair(left: "b", right: "c"), Pair(left: "c", right: "d")]


How can this swift code be made shorter or simpler?

Answer
zip(votes, votes.dropFirst())

This produces a sequence of tuples.

Example

struct Pair {
    let left: String
    let right: String
}
let votes = ["a", "b", "c", "d"]
let pairs = zip(votes, votes.dropFirst()).map {
    Pair(left: $0, right: $1)
}
print(pairs)
// [Pair(left: "a", right: "b"), Pair(left: "b", right: "c"), Pair(left: "c", right: "d")]