Swift. Sort array of structs using property name from string variable

Question

I have simple code:

struct User {
    let id: Int
    let name: String
}

var users: [User] = [User(id:1, name:"Alpha"), User(id:2, name:"Beta"), User(id:3, name:"Gamma")]

print(users)
users.sort { $0.name > $1.name }
print(users)

What is the best way of changing the sorting field based on variable? I mean, I want to have some variable like "sortBy" which contains value of sorting field ("id", "name" etc, struct may contain dozens of fields). And I can't find out the proper way of doing so in Swift.

Pseudo-code:

var sortBy = "name"
users.sort { $0.{sortBy} > $1.{sortBy} }

user652038 · Accepted Answer · 2022-05-26 23:21:07Z

1

Use key paths and methods.

users.sort(by: \.name)
users.sort(by: \.id)

extension Array where Element == User {
  mutating func sort<Comparable: Swift.Comparable>(
    by comparable: (Element) throws -> Comparable
  ) rethrows {
    self = try sorted(by: comparable, >)
  }
}

public extension Sequence {
  /// Sorted by a common `Comparable` value, and sorting closure.
  func sorted<Comparable: Swift.Comparable>(
    by comparable: (Element) throws -> Comparable,
    _ areInIncreasingOrder: (Comparable, Comparable) throws -> Bool
  ) rethrows -> [Element] {
    try sorted {
      try areInIncreasingOrder(comparable($0), comparable($1))
    }
  }
}

answered May 26, 2022 at 23:21

user652038

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