I have an array from 0 to 100.
let array = ["0", "1", "2", "3", "4", "5", "6", "7", "8", "9"...."100"]
now, I want to add "-" after every 3 objects in an array.
So the output would be like this
array = ["0", "1", "2","-","3", "4", "5","-", "6", "7", "8", "-","9"...."100"]
So, How can I achieve this?
and what if i have model array instead of String array?
struct SubCategory {
var title: String = ""
var subTitle: String = ""
}
let array = [SubCategory]()
let array = ["0", "1", "2", "3", "4", "5", "6", "7", "8", "9", "10"]
extension Array {
func chunks(of size: Int) -> [[Element]] {
return stride(from: 0, to: count, by: size).map {
let n = Swift.min(size, count - $0)
return Array(self[$0 ..< $0 + n])
}
}
}
let joined = Array(array.chunks(of: 3).joined(separator: ["-"]))
["0", "1", "2", "3", "4", "5", "6", "7", "8", "9", "10", "11"] then output is ["0", "1", "2", "-", "3", "4", "5", "-", "6", "7", "8", "-", "9", "1", "0", "1", "1"] which is not right.
Here is a way to directly create the result with a single map and a bit of math:
extension Array {
func adding(_ element: Element, afterEvery n: Int) -> [Element] {
guard n > 0 else { fatalError("afterEvery value must be greater than 0") }
let newcount = self.count + self.count / n
return (0 ..< newcount).map { (i: Int) -> Element in
(i + 1) % (n + 1) == 0 ? element : self[i - i / (n + 1)]
}
}
}
Example:
let result = ["0", "1", "2", "3", "4", "5", "6"].adding("-", afterEvery: 3)
print(result)
Output:
["0", "1", "2", "-", "3", "4", "5", "-", "6"]
Example 2:
This time with [Int]:
let result2 = [1, 2, 3, 4, 5, 6].adding(0, afterEvery: 2)
print(result2)
Output:
[1, 2, 0, 3, 4, 0, 5, 6, 0]
Example 3:
With a custom struct:
struct SubCategory: CustomStringConvertible {
var title = ""
var subTitle = ""
var description: String { return "SubCategory(title: \(title), subTitle: \(subTitle)" }
}
let array: [SubCategory] = [
SubCategory(title: "2001", subTitle: "A Space Odyssey"),
SubCategory(title: "Star Wars Episode 1", subTitle: "The Phantom Menace"),
SubCategory(title: "Star Wars Episode 2", subTitle: "Attack of the Clones"),
SubCategory(title: "Star Wars Episode 3", subTitle: "Revenge of the Sith"),
SubCategory(title: "Star Wars Episode 4", subTitle: "A New Hope"),
SubCategory(title: "Star Wars Episode 5", subTitle: "The Empire Strikes Back"),
SubCategory(title: "Star Wars Episode 6", subTitle: "Return of the Jedi")
]
let result3 = array.adding(SubCategory(title: "none", subTitle: "none"), afterEvery: 3)
print(result3)
Output:
[SubCategory(title: 2001, subTitle: A Space Odyssey, SubCategory(title: Star Wars Episode 1, subTitle: The Phantom Menace, SubCategory(title: Star Wars Episode 2, subTitle: Attack of the Clones, SubCategory(title: none, subTitle: none, SubCategory(title: Star Wars Episode 3, subTitle: Revenge of the Sith, SubCategory(title: Star Wars Episode 4, subTitle: A New Hope, SubCategory(title: Star Wars Episode 5, subTitle: The Empire Strikes Back, SubCategory(title: none, subTitle: none, SubCategory(title: Star Wars Episode 6, subTitle: Return of the Jedi]
Mutating version
Here is a version that mutates the original array instead of creating a new one:
extension Array {
mutating func add(_ element: Element, afterEvery n: Int) {
guard n > 0 else { fatalError("afterEvery value must be greater than 0") }
var index = (self.count / n) * n
while index > 0 {
self.insert(element, at: index)
index -= n
}
}
}
Example:
var array = ["0", "1", "2", "3", "4", "5", "6"]
array.add("-", afterEvery: 3)
print(array)
Output:
["0", "1", "2", "-", "3", "4", "5", "-", "6"]
