Swift: 'Hashable.Hashvalue' Is Deprecated as a Protocol Requirement;

Swift: 'Hashable.hashValue' is deprecated as a protocol requirement;

As the warning says, now you should implement the hash(into:) function instead.

func hash(into hasher: inout Hasher) {
    switch self {
    case .mention: hasher.combine(-1)
    case .hashtag: hasher.combine(-2)
    case .url: hasher.combine(-3)
    case .custom(let regex): hasher.combine(regex) // assuming regex is a string, that already conforms to hashable
    }
}

It would be even better (in case of enums and struct) to remove the custom hash(into:) implementation (unless you need a specific implementation) as the compiler will automatically synthesize it for you.

Just make your enum conforming to it:

public enum ActiveType: Hashable {
    case mention
    case hashtag
    case url
    case custom(pattern: String)

    var pattern: String {
        switch self {
        case .mention: return RegexParser.mentionPattern
        case .hashtag: return RegexParser.hashtagPattern
        case .url: return RegexParser.urlPattern
        case .custom(let regex): return regex
        }
    }
}

Hashable.hashValue' is deprecated as a protocol requirement; conform type 'CarnivalWheel' to 'Hashable' by implementing 'hash(into:)' instead

func hash(into hasher: inout Hasher) {
        hasher.combine(ObjectIdentifier(self))
    }

will add conformance.

How to Implement hash(into:) from hashValue in Swift?

You can simply use hasher.combine and call it with the values you want to use for hashing:

func hash(into hasher: inout Hasher) {
    hasher.combine(index)
    hasher.combine(title)
}

why do i receive this warning to implement 'hash(into:)' on a type that conforms to a protocol with at default implementation

This code has two default implementations for hash(into:). One from Int, and one from SettingSelectable.

I'm not certain if this is defined behavior. My expectation is that the Int implementation is used and the SettingsSelectable extension is ignored. In any case, the diagnostic is not very good. I suggest opening a defect about that.

You can fix this error by removing the Int, or by explicitly implementing hash(into:) so it's clear which one you mean. Or you could create another layer of protocols:

protocol SettingsSelectableBase: Hashable, Settingsable {
  var display: String { get }
}

protocol SettingsSelectable: SettingsSelectableBase {}

// Only give the default to things that ask for it, not to Base conformers
extension SettingsSelectable {
  func hash(into hasher: inout Hasher) {
    hasher.combine(display)
  }
}

extension SettingsSelectableBase {
    func resetSettings() {
      print("These have been reset")
    }
}

enum PlaybackSpeed: Int, SettingsSelectableBase { ... }

What is the use of hashable protocol in swift4?

To make an object conform to Hashable we need to provide a hashValue property that will return a unique, consistent number for each instance.
The Hashable protocol inherits from Equatable, so you may also need to implement an == function.

Note: If two objects compare as equal using == they should also generate the same hash value, but the reverse isn’t true – hash collisions can happen.

Before Swift 4.1, conforming to Hashable was complex because you needed to calculate a hashValue property by hand.
In Swift 4.1 this improved so that hashValue could be synthesized on your behalf if all the properties conform to Hashable .
Swift 4.2 introduces a new Hasher struct that provides a randomly seeded, universal hash function to make all our lives easier. Refer for more

Conforming to Hashable protocol?

You're missing the declaration:

struct DateStruct: Hashable {

And your == function is wrong. You should compare the three properties.

static func == (lhs: DateStruct, rhs: DateStruct) -> Bool {
    return lhs.year == rhs.year && lhs.month == rhs.month && lhs.day == rhs.day
}

It's possible for two different values to have the same hash value.

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