This Hashable package defines a class, Hashable, for types that can be converted to a hash value. This class exists for the benefit of hashing-based data structures. The package provides instances for basic types and a way to combine hash values.
Questions tagged [hashable]
161 questions
2
votes
1 answer
Set of hashable custom elements inserts equal elements
Setup:
I want to use a Set of the following struct:
struct NumberPair: Hashable {
let n1: Int
let n2: Int
static func == (lhs: NumberPair, rhs: NumberPair) -> Bool {
lhs.n1 == rhs.n1 && lhs.n2 == rhs.n2 ||
lhs.n2 ==…
Reinhard Männer
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2
votes
1 answer
SwiftUI enum String, Codable, Hashable Error
import SwiftUI
import Foundation
import Combine
import CoreLocation
struct structuralCodes: Hashable, Codable, Identifiable {
var id = UUID()
var index: Int
var title: String
var icon: String
var isFeatured: Bool
var…
officer_Krupke
- 27
- 4
2
votes
2 answers
How detect hashable types with structural pattern matching?
Using structural pattern matching, how do you write a case that matches instances of hashable types?
I've tried:
for obj in [], (), set(), frozenset(), 10, None, dict():
match obj:
case object(__hash__=_):
print('Hashable…
Raymond Hettinger
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2
votes
2 answers
How to add the Hashable protocol to CLLocationCoordinate2D using an extension in SwiftUI
So I have a custom struct with one property of type String and another of type CLLocationCoordinate2D. Apparently, String conforms to Hashable and if I can extend CLLocationCoordinate2D to conform to Hashable, my custom struct will also be Hashable.…
nickcoding
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2
votes
2 answers
Immutable hashable list with correct typings
I need to use sequence of items as dict key and to feat List[...] type. If I use tuple, than it does not feat to a List[...] type and I cannot use Tuple[...] type, because tuple length is not known.
Is there any class (maybe from a 3rd party…
Yaroslav Kishchenko
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2
votes
1 answer
Swift - Can I make a protocol Hashable?
I have written a simple protocol Data :
public protocol Data {
var state: [String: Any] { get set }
var objectId: String? { get set }
}
public extension Data {
var objectId: String? {
get {
return…
Another Dude
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2
votes
2 answers
Why don't functions preserve identity?
I was wondering why Python 3.7 functions behave in a rather strange way. I think it's kinda weird and contradictory to the whole notion of hashability. Let me clarify what I encounter with a simple example code. Knowing that tuples are hashable,…
Ashkan Ranjbar
- 184
- 7
2
votes
1 answer
Swift: Using ObjectID of class for hashable protocol results in random behaviour in set.contains method. What is wrong with the code?
I have a small number of instances of a custom class stored in a set. I need to check if a certain element is contained in that set. The criteria for a match must be the object's ID, not its content.
For simplification assume a class with an integer…
MassMover
- 529
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2
votes
1 answer
Cache results of Swift hash(into:) Hashable protocol requirement
I have a class being heavily used in Sets and Dictionaries.
For performance reasons this class implements Hashable in a old way and caches the computed hash:
let hashValue: Int
init(...) {
self.hashValue = ...
}
In Xcode 10.2 I see a warning,…
Tim
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2
votes
1 answer
Why do set operators work with dict_key view objects but not the equivalent set methods?
Edit: Possible duplicate. Only after posting this question and looking in "related questions" was I able to find Why are set methods like .intersection() not supported on set-like objects?, this question may similar enough to be a duplicate.
I am…
johnDanger
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2
votes
1 answer
Swift - A Decimal's hashValue is the same for X == -X, cannot be used for comparing hashValues
We found out that you cannot distinguish two Decimals by their hashValue if one is the negative of the other. We use Decimals as a field in a struct and that struct implements Hashable to be able to be put in a set. Our business logic then requires…
Simon
- 470
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2
votes
2 answers
Override Equatable and Hashable in Swift
Is there a way to override Equatable of NSManagedObject? I have a coredata dataset of 300k objects and I need to remove duplicates base on the object's business id.
// Coredata NSManagedObject
import Foundation
import…
Unikorn
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2
votes
1 answer
How can I update this Hashable.hashValue to conform to new requirements.?
I'm trying to fix up an old tutorial from RayWenderlich's site, no longer supported.
The warning appears in three files, Chain.swift, Cookie.swift and Swap.swift from the "How to Make a Game Like Candy Crush with SpriteKit and Swift:" tutorial
I'm…
Harry McGovern
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2
votes
0 answers
The Hashable now want to use protocol instead of hashValue but I can't figure it out
I use to have the following code that worked in Swift 4.2 but is now deprecated in Swift 5:
struct xxx: Hashable {
var hashValue: Int {return uniqueIdentifier}
When I try to use the new hash(into hasher: inout Hasher) I'm not sure what to do.…
mretondo
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2
votes
1 answer
Why does struct need to conform to Hashable as well as Generic array when converting to a dictionary
The goal was to convert items in a generic list into a dictionary for the variable uniqueKeys, but I saw the error:
Cannot subscript a value of incorrect or ambiguous type
I knew something needed to conform to the Hashable protocol and eventually…
Turnipdabeets
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