How to sort an array by a specific key - arrays

Question

I am using swapi.co as my source of json data and my response looks like the following: https://swapi.co/api/people/
My array of "characters" has the structure
// MARK: - CharactersResult
struct CharactersResult: Codable {
let name, height, mass, hairColor: String
let skinColor, eyeColor, birthYear: String
let gender: Gender
let homeworld: String
let films, species, vehicles, starships: [String]
let created, edited: String
let url: String
enum CodingKeys: String, CodingKey {
case name, height, mass
case hairColor = "hair_color"
case skinColor = "skin_color"
case eyeColor = "eye_color"
case birthYear = "birth_year"
case gender, homeworld, films, species, vehicles, starships, created, edited, url
}
}
I would like to get the smallest character and the largest out of my array. My function is:
func getCharacters(urlToGet: String){
do{
if let url = URL(string: urlToGet) {
URLSession.shared.dataTask(with: url) { data, response, error in
if let data = data {
do {
let jsonCharacters = try JSONDecoder().decode(Characters.self, from: data)
self.characters = self.characters + jsonCharacters.results
self.nextPageUrlForCharacters = jsonCharacters.next
self.updatePicker()
} catch let error {
print(error)
}
}
}.resume()
}
}
}
My main question is where to do the sorting and what is the most efficient way to get the smallest and the largest character.

Answer 1

Assuming smallest and largest is related to the height of the character (then shortest and tallest are more appropriate), sort the array by that struct member. As the value is String you have to add the .numeric option.
The descending order starts with the largest value
let sortedCharacters = self.characters.sorted{$0.height.compare($1.height, options: .numeric) == .orderedDescending}
let tallestCharacter = sortedCharacters.first
let shortestCharacter = sortedCharacters.last
Side note: You can get rid of the CodingKeys if you add the convertFromSnakeCase key decoding strategy.

Answer 2

This simplified version of your code illustrates how to sort by an arbitrary key, as long as that key is Comparable (so I've made your height and mass properties both Ints rather than String):
struct MovieCharacter: Codable {
let name: String
let height: Int
let mass: Int
}
let fred = MovieCharacter(name: "Fred", height: 123, mass: 99)
let wilma = MovieCharacter(name: "Wilma", height: 158, mass: 47)
let chars = [fred, wilma]
let heaviestToLightest = chars.sorted { $0.mass > $1.mass }
// Prints "Fred, Wilma"
print(heaviestToLightest.map { $0.name }.joined(separator: ", "))
let tallestToShortest = chars.sorted { $0.height > $1.height }
// prints "Wilma, Fred"
print(tallestToShortest.map { $0.name }.joined(separator: ", "))
To change the sort order, reverse the >' in the comparison closure. If you want to know the "most" and "least" of a particular order, use.firstand.last` on the result.
Also, to save yourself from having to maintain the CodingKeys enum, use .keyDecodingStrategy of a JSONDecoder:
let decoder = JSONDecoder()
decoder.keyDecodingStrategy = .convertFromSnakeCase
let characters = try decoder.decode(Characters.self, from: jsonData)