Methods on enums by using extension methods: Unity sample MonoBehaviour explaining how to associate simple strings with enums.
Posted by jpluimers on 2021/07/29
Reminder to self (as I keep forgetting how versatile extension methods can be):
[WayBack] Mark Pintar sur Twitter : “The nice thing about extension methods is one can add it to most types. Even works of int, float and other primitive types… “
An interesting way of allowing methods on enumerated types is by using extension methods: [WayBack] Unity sample MonoBehaviour explaining how to associate simple strings with enums. · GitHub.
A more elaborate example from [WayBack] NoraGrace-Chess/Position.cs at master · ericoldre/NoraGrace-Chess · GitHub is below the fold.
Via:
- [WayBack] Freya Holmér on Twitter: “Did you know enum types support functions in C#? It’s a neat little trick using extension methods~✨ #unity3d #unitytips… “
- [WayBack] Eric Oldre on Twitter: „I used this technique EXTENSIVELY when developing my C# chess engine for representing positions, ranks, files, players, etc with type safety. (instead of ints)…“
- all from this great thread[WayBack] Freya Holmér on Twitter: “Did you know enum types support functions in C#? It’s a neat little trick using extension methods~✨ #unity3d #unitytips… “
using System; using System.ComponentModel; using UnityEngine; public class EnumDescription : MonoBehaviour { public enum PlayerState { Unknown, [Description("Alive and kicking")] Alive, [Description("Dead as a duck")] Dead } // Start is called before the first frame update void Start() { var state = PlayerState.Dead; Debug.Log("Player is " + state.GetDescription()); } } public static class EnumExtensions { public static string GetDescription(this Enum value) { var type = value.GetType(); var name = Enum.GetName(type, value); if (name != null) { var field = type.GetField(name); if (field != null) { if (Attribute.GetCustomAttribute(field, typeof(DescriptionAttribute)) is DescriptionAttribute attr) return attr.Description; } } return name; } }
using System; using System.Collections.Generic; using System.Linq; using System.Text; namespace NoraGrace.Engine { public enum Position { A8 = 0, B8 = 1, C8 = 2, D8 = 3, E8 = 4, F8 = 5, G8 = 6, H8 = 7, A7 = 8, B7 = 9, C7 = 10, D7 = 11, E7 = 12, F7 = 13, G7 = 14, H7 = 15, A6 = 16, B6 = 17, C6 = 18, D6 = 19, E6 = 20, F6 = 21, G6 = 22, H6 = 23, A5 = 24, B5 = 25, C5 = 26, D5 = 27, E5 = 28, F5 = 29, G5 = 30, H5 = 31, A4 = 32, B4 = 33, C4 = 34, D4 = 35, E4 = 36, F4 = 37, G4 = 38, H4 = 39, A3 = 40, B3 = 41, C3 = 42, D3 = 43, E3 = 44, F3 = 45, G3 = 46, H3 = 47, A2 = 48, B2 = 49, C2 = 50, D2 = 51, E2 = 52, F2 = 53, G2 = 54, H2 = 55, A1 = 56, B1 = 57, C1 = 58, D1 = 59, E1 = 60, F1 = 61, G1 = 62, H1 = 63, OUTOFBOUNDS = 64 } public static class PositionUtil { public const int LookupArrayLength = 64; public static readonly Position[] AllPositions = new Position[]{ Position.A8,Position.B8,Position.C8,Position.D8,Position.E8,Position.F8,Position.G8,Position.H8, Position.A7,Position.B7,Position.C7,Position.D7,Position.E7,Position.F7,Position.G7,Position.H7, Position.A6,Position.B6,Position.C6,Position.D6,Position.E6,Position.F6,Position.G6,Position.H6, Position.A5,Position.B5,Position.C5,Position.D5,Position.E5,Position.F5,Position.G5,Position.H5, Position.A4,Position.B4,Position.C4,Position.D4,Position.E4,Position.F4,Position.G4,Position.H4, Position.A3,Position.B3,Position.C3,Position.D3,Position.E3,Position.F3,Position.G3,Position.H3, Position.A2,Position.B2,Position.C2,Position.D2,Position.E2,Position.F2,Position.G2,Position.H2, Position.A1,Position.B1,Position.C1,Position.D1,Position.E1,Position.F1,Position.G1,Position.H1, }; public static Position Parse(string s) { if (s.Length != 2) { throw new ArgumentException(s + " is not a valid position"); } File file = FileUtil.Parse(s[0]); Rank rank = RankUtil.Parse(s[1]); return file.ToPosition(rank); } public static bool IsLight(this Position pos) { bool retval = (int)pos % 2 == 1; switch (pos.ToRank()) { case Rank.Rank2: case Rank.Rank4: case Rank.Rank6: case Rank.Rank8: retval = !retval; break; } return retval; } public static bool IsInBounds(this Position pos) { return (int)pos >= 0 && (int)pos <= 63; } public static Rank ToRank(this Position pos) { //AssertPosition(pos); return (Rank)(((int)pos / 8)); } public static File ToFile(this Position pos) { //AssertPosition(pos); return (File)((int)pos % 8); } public static string Name(this Position pos) { return pos.ToFile().FileToString() + pos.ToRank().RankToString(); } public static Bitboard ToBitboard(this Position position) { if (position.IsInBounds()) { return (Bitboard)((ulong)1 << position.GetIndex64()); } else { return (Bitboard.Empty); } } public static int DistanceTo(this Position thisPosition, Position otherPosition) { int rDiff = Math.Abs((int)thisPosition.ToRank() - (int)otherPosition.ToRank()); int fDiff = Math.Abs((int)thisPosition.ToFile() - (int)otherPosition.ToFile()); return rDiff > fDiff ? rDiff : fDiff; } public static int DistanceToNoDiag(this Position thisPosition, Position otherPosition) { int rDiff = Math.Abs((int)thisPosition.ToRank() - (int)otherPosition.ToRank()); int fDiff = Math.Abs((int)thisPosition.ToFile() - (int)otherPosition.ToFile()); return rDiff + fDiff; } public static int GetIndex64(this Position position) { return (int)position; } public static Bitboard ToBitboard(this IEnumerable positions) { Bitboard bitboard = 0; foreach (var position in positions) { bitboard |= position.ToBitboard(); } return bitboard; } public static Bitboard Between(this Position from, Position to) { Direction dir = from.DirectionTo(to); Bitboard retval = Bitboard.Empty; if (dir != 0) { while (from != to) { from = from.PositionInDirectionUnsafe(dir); retval |= from.ToBitboard(); } } return retval & ~to.ToBitboard(); } public static Direction DirectionTo(this Position from, Position to) { Rank rankfrom = from.ToRank(); File filefrom = from.ToFile(); Rank rankto = to.ToRank(); File fileto = to.ToFile(); if (fileto == filefrom) { if (rankfrom < rankto) { return Direction.DirS; } return Direction.DirN; } else if (rankfrom == rankto) { if (filefrom > fileto) { return Direction.DirW; } return Direction.DirE; } int rankchange = rankto - rankfrom; int filechange = fileto - filefrom; int rankchangeabs = rankchange > 0 ? rankchange : -rankchange; int filechangeabs = filechange > 0 ? filechange : -filechange; if ((rankchangeabs == 1 && filechangeabs == 2) || (rankchangeabs == 2 && filechangeabs == 1)) { //knight direction return (Direction)((int)rankchange * 8) + (int)filechange; } else if (rankchangeabs != filechangeabs) { return 0; } if (rankchange < 0) { if (filechange > 0) { return Direction.DirNE; } return Direction.DirNW; } else { if (filechange > 0) { return Direction.DirSE; } return Direction.DirSW; } } public static Position PositionInDirectionUnsafe(this Position pos, Direction dir) { return (Position)((int)pos + (int)dir); } public static Position PositionInDirection(this Position pos, Direction dir) { if (!pos.IsInBounds()) { return Position.OUTOFBOUNDS; } File file = pos.ToFile(); Rank rank = pos.ToRank(); switch (dir) { case Direction.DirN: rank -= 1; break; case Direction.DirE: file += 1; break; case Direction.DirS: rank += 1; break; case Direction.DirW: file -= 1; break; case Direction.DirNE: rank -= 1; file += 1; break; case Direction.DirSE: rank += 1; file += 1; break; case Direction.DirSW: rank += 1; file -= 1; break; case Direction.DirNW: rank -= 1; file -= 1; break; case Direction.DirNNE: rank -= 2; file += 1; break; case Direction.DirEEN: rank -= 1; file += 2; break; case Direction.DirEES: rank += 1; file += 2; break; case Direction.DirSSE: rank += 2; file += 1; break; case Direction.DirSSW: rank += 2; file -= 1; break; case Direction.DirWWS: rank += 1; file -= 2; break; case Direction.DirWWN: rank -= 1; file -= 2; break; case Direction.DirNNW: rank -= 2; file -= 1; break; default: return (Position.OUTOFBOUNDS); } if (rank.IsInBounds() && file.IsInBounds()) { return rank.ToPosition(file); } else { return (Position.OUTOFBOUNDS); } } public static Position Reverse(this Position pos) { Rank r = pos.ToRank(); File f = pos.ToFile(); Rank newrank = Rank.EMPTY; switch (r) { case Rank.Rank1: newrank = Rank.Rank8; break; case Rank.Rank2: newrank = Rank.Rank7; break; case Rank.Rank3: newrank = Rank.Rank6; break; case Rank.Rank4: newrank = Rank.Rank5; break; case Rank.Rank5: newrank = Rank.Rank4; break; case Rank.Rank6: newrank = Rank.Rank3; break; case Rank.Rank7: newrank = Rank.Rank2; break; case Rank.Rank8: newrank = Rank.Rank1; break; } return f.ToPosition(newrank); } } public sealed class ChessPositionDictionary { [System.Xml.Serialization.XmlIgnore()] private T[] _values = new T[64]; public ChessPositionDictionary() { } public ChessPositionDictionary(params T[] initVals) { for (int i = 0; i < 63; i++) { _values[i] = initVals[i]; } } [System.Xml.Serialization.XmlIgnore()] public T this[Position pos] { get { return _values[(int)pos]; } set { _values[(int)pos] = value; } } public T A1 { get { return this[Position.A1]; } set { this[Position.A1] = value; } } public T A2 { get { return this[Position.A2]; } set { this[Position.A2] = value; } } public T A3 { get { return this[Position.A3]; } set { this[Position.A3] = value; } } public T A4 { get { return this[Position.A4]; } set { this[Position.A4] = value; } } public T A5 { get { return this[Position.A5]; } set { this[Position.A5] = value; } } public T A6 { get { return this[Position.A6]; } set { this[Position.A6] = value; } } public T A7 { get { return this[Position.A7]; } set { this[Position.A7] = value; } } public T A8 { get { return this[Position.A8]; } set { this[Position.A8] = value; } } public T B1 { get { return this[Position.B1]; } set { this[Position.B1] = value; } } public T B2 { get { return this[Position.B2]; } set { this[Position.B2] = value; } } public T B3 { get { return this[Position.B3]; } set { this[Position.B3] = value; } } public T B4 { get { return this[Position.B4]; } set { this[Position.B4] = value; } } public T B5 { get { return this[Position.B5]; } set { this[Position.B5] = value; } } public T B6 { get { return this[Position.B6]; } set { this[Position.B6] = value; } } public T B7 { get { return this[Position.B7]; } set { this[Position.B7] = value; } } public T B8 { get { return this[Position.B8]; } set { this[Position.B8] = value; } } public T C1 { get { return this[Position.C1]; } set { this[Position.C1] = value; } } public T C2 { get { return this[Position.C2]; } set { this[Position.C2] = value; } } public T C3 { get { return this[Position.C3]; } set { this[Position.C3] = value; } } public T C4 { get { return this[Position.C4]; } set { this[Position.C4] = value; } } public T C5 { get { return this[Position.C5]; } set { this[Position.C5] = value; } } public T C6 { get { return this[Position.C6]; } set { this[Position.C6] = value; } } public T C7 { get { return this[Position.C7]; } set { this[Position.C7] = value; } } public T C8 { get { return this[Position.C8]; } set { this[Position.C8] = value; } } public T D1 { get { return this[Position.D1]; } set { this[Position.D1] = value; } } public T D2 { get { return this[Position.D2]; } set { this[Position.D2] = value; } } public T D3 { get { return this[Position.D3]; } set { this[Position.D3] = value; } } public T D4 { get { return this[Position.D4]; } set { this[Position.D4] = value; } } public T D5 { get { return this[Position.D5]; } set { this[Position.D5] = value; } } public T D6 { get { return this[Position.D6]; } set { this[Position.D6] = value; } } public T D7 { get { return this[Position.D7]; } set { this[Position.D7] = value; } } public T D8 { get { return this[Position.D8]; } set { this[Position.D8] = value; } } public T E1 { get { return this[Position.E1]; } set { this[Position.E1] = value; } } public T E2 { get { return this[Position.E2]; } set { this[Position.E2] = value; } } public T E3 { get { return this[Position.E3]; } set { this[Position.E3] = value; } } public T E4 { get { return this[Position.E4]; } set { this[Position.E4] = value; } } public T E5 { get { return this[Position.E5]; } set { this[Position.E5] = value; } } public T E6 { get { return this[Position.E6]; } set { this[Position.E6] = value; } } public T E7 { get { return this[Position.E7]; } set { this[Position.E7] = value; } } public T E8 { get { return this[Position.E8]; } set { this[Position.E8] = value; } } public T F1 { get { return this[Position.F1]; } set { this[Position.F1] = value; } } public T F2 { get { return this[Position.F2]; } set { this[Position.F2] = value; } } public T F3 { get { return this[Position.F3]; } set { this[Position.F3] = value; } } public T F4 { get { return this[Position.F4]; } set { this[Position.F4] = value; } } public T F5 { get { return this[Position.F5]; } set { this[Position.F5] = value; } } public T F6 { get { return this[Position.F6]; } set { this[Position.F6] = value; } } public T F7 { get { return this[Position.F7]; } set { this[Position.F7] = value; } } public T F8 { get { return this[Position.F8]; } set { this[Position.F8] = value; } } public T G1 { get { return this[Position.G1]; } set { this[Position.G1] = value; } } public T G2 { get { return this[Position.G2]; } set { this[Position.G2] = value; } } public T G3 { get { return this[Position.G3]; } set { this[Position.G3] = value; } } public T G4 { get { return this[Position.G4]; } set { this[Position.G4] = value; } } public T G5 { get { return this[Position.G5]; } set { this[Position.G5] = value; } } public T G6 { get { return this[Position.G6]; } set { this[Position.G6] = value; } } public T G7 { get { return this[Position.G7]; } set { this[Position.G7] = value; } } public T G8 { get { return this[Position.G8]; } set { this[Position.G8] = value; } } public T H1 { get { return this[Position.H1]; } set { this[Position.H1] = value; } } public T H2 { get { return this[Position.H2]; } set { this[Position.H2] = value; } } public T H3 { get { return this[Position.H3]; } set { this[Position.H3] = value; } } public T H4 { get { return this[Position.H4]; } set { this[Position.H4] = value; } } public T H5 { get { return this[Position.H5]; } set { this[Position.H5] = value; } } public T H6 { get { return this[Position.H6]; } set { this[Position.H6] = value; } } public T H7 { get { return this[Position.H7]; } set { this[Position.H7] = value; } } public T H8 { get { return this[Position.H8]; } set { this[Position.H8] = value; } } public override bool Equals(object obj) { ChessPositionDictionary other = obj as ChessPositionDictionary; if (other == null) { return false; } foreach (Position pos in PositionUtil.AllPositions) { if (!this[pos].Equals(other[pos])) { return false; } } return true; } public override int GetHashCode() { unchecked // Overflow is fine, just wrap { int hash = 17;//randomly choosen prime foreach (Position pos in PositionUtil.AllPositions) { T field = this[pos]; int fieldHash = 6823; //randomly choosen prime if (field != null) { fieldHash = field.GetHashCode(); } hash = (hash * 23) + fieldHash; } return hash; } } } }
–jeroen
The Wiert Corner - irregular stream of stuff 
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