Move statics to RulesetCollection to avoid conflicts later on.

osu.Desktop.Tests/VisualTests.cs

@@ -20,10 +20,10 @@ namespace osu.Desktop.Tests
         {
             using (var host = new HeadlessGameHost())
             {
-                Ruleset.Register(new OsuRuleset());
+                RulesetCollection.Register(typeof(OsuRuleset));
-                Ruleset.Register(new TaikoRuleset());
+                RulesetCollection.Register(typeof(TaikoRuleset));
-                Ruleset.Register(new ManiaRuleset());
+                RulesetCollection.Register(typeof(ManiaRuleset));
-                Ruleset.Register(new CatchRuleset());
+                RulesetCollection.Register(typeof(CatchRuleset));
 
                 host.Run(new AutomatedVisualTestGame());
             }

osu.Desktop.VisualTests/Program.cs

@@ -21,10 +21,10 @@ namespace osu.Desktop.VisualTests
 
             using (GameHost host = Host.GetSuitableHost(@"osu"))
             {
-                Ruleset.Register(new OsuRuleset());
+                RulesetCollection.Register(typeof(OsuRuleset));
-                Ruleset.Register(new TaikoRuleset());
+                RulesetCollection.Register(typeof(TaikoRuleset));
-                Ruleset.Register(new ManiaRuleset());
+                RulesetCollection.Register(typeof(ManiaRuleset));
-                Ruleset.Register(new CatchRuleset());
+                RulesetCollection.Register(typeof(CatchRuleset));
 
                 if (benchmark)
                     host.Run(new AutomatedVisualTestGame());

osu.Desktop/Program.cs

@@ -41,10 +41,10 @@ namespace osu.Desktop
                 }
                 else
                 {
-                    Ruleset.Register(new OsuRuleset());
+                    RulesetCollection.Register(typeof(OsuRuleset));
-                    Ruleset.Register(new TaikoRuleset());
+                    RulesetCollection.Register(typeof(TaikoRuleset));
-                    Ruleset.Register(new ManiaRuleset());
+                    RulesetCollection.Register(typeof(ManiaRuleset));
-                    Ruleset.Register(new CatchRuleset());
+                    RulesetCollection.Register(typeof(CatchRuleset));
 
                     host.Run(new OsuGameDesktop(args));
                 }

osu.Game.Tests/Beatmaps/Formats/OsuLegacyDecoderTest.cs

@@ -22,7 +22,7 @@ namespace osu.Game.Tests.Beatmaps.Formats
         public void SetUp()
         {
             OsuLegacyDecoder.Register();
-            Ruleset.Register(new OsuRuleset());
+            RulesetCollection.Register(typeof(OsuRuleset));
         }
 
         [Test]

osu.Game.Tests/Beatmaps/IO/ImportBeatmapTest.cs

@@ -28,10 +28,10 @@ namespace osu.Game.Tests.Beatmaps.IO
         [OneTimeSetUp]
         public void SetUp()
         {
-            Ruleset.Register(new OsuRuleset());
+            RulesetCollection.Register(typeof(OsuRuleset));
-            Ruleset.Register(new TaikoRuleset());
+            RulesetCollection.Register(typeof(TaikoRuleset));
-            Ruleset.Register(new ManiaRuleset());
+            RulesetCollection.Register(typeof(ManiaRuleset));
-            Ruleset.Register(new CatchRuleset());
+            RulesetCollection.Register(typeof(CatchRuleset));
         }
 
         [Test]

osu.Game.Tests/Beatmaps/IO/OszArchiveReaderTest.cs

@@ -19,7 +19,7 @@ namespace osu.Game.Tests.Beatmaps.IO
         public void SetUp()
         {
             OszArchiveReader.Register();
-            Ruleset.Register(new OsuRuleset());
+            RulesetCollection.Register(typeof(OsuRuleset));
         }
 
         [Test]

osu.Game/Beatmaps/Beatmap.cs

@@ -54,7 +54,7 @@ namespace osu.Game.Beatmaps
         /// Calculates the star difficulty for this Beatmap.
         /// </summary>
         /// <returns>The star difficulty.</returns>
-        public double CalculateStarDifficulty() => Ruleset.GetRuleset(BeatmapInfo.Mode).CreateDifficultyCalculator(this).Calculate();
+        public double CalculateStarDifficulty() => RulesetCollection.GetRuleset(BeatmapInfo.Mode).CreateDifficultyCalculator(this).Calculate();
 
         /// <summary>
         /// Constructs a new beatmap.

osu.Game/Beatmaps/Drawables/DifficultyIcon.cs

@@ -45,7 +45,7 @@ namespace osu.Game.Beatmaps.Drawables
                     Origin = Anchor.Centre,
                     TextSize = Size.X,
                     Colour = Color4.White,
-                    Icon = Ruleset.GetRuleset(beatmap.Mode).Icon
+                    Icon = RulesetCollection.GetRuleset((int)beatmap.Mode).Icon
                 }
             };
         }

osu.Game/Database/ScoreDatabase.cs

@@ -39,7 +39,7 @@ namespace osu.Game.Database
             using (Stream s = storage.GetStream(Path.Combine(replay_folder, replayFilename)))
             using (SerializationReader sr = new SerializationReader(s))
             {
-                var ruleset = Ruleset.GetRuleset((PlayMode)sr.ReadByte());
+                var ruleset = RulesetCollection.GetRuleset((PlayMode)sr.ReadByte());
                 score = ruleset.CreateScoreProcessor().CreateScore();
 
                 /* score.Pass = true;*/

osu.Game/Modes/Ruleset.cs

@@ -22,10 +22,6 @@ namespace osu.Game.Modes
 
     public abstract class Ruleset
     {
-        private static readonly ConcurrentDictionary<PlayMode, Type> available_rulesets = new ConcurrentDictionary<PlayMode, Type>();
-
-        public static IEnumerable<PlayMode> PlayModes => available_rulesets.Keys;
-
         public virtual IEnumerable<BeatmapStatistic> GetBeatmapStatistics(WorkingBeatmap beatmap) => new BeatmapStatistic[] { };
 
         public abstract IEnumerable<Mod> GetModsFor(ModType type);
@@ -36,8 +32,6 @@ namespace osu.Game.Modes
 
         public abstract ScoreProcessor CreateScoreProcessor();
 
-        public static void Register(Ruleset ruleset) => available_rulesets.TryAdd(ruleset.PlayMode, ruleset.GetType());
-
         protected abstract PlayMode PlayMode { get; }
 
         public virtual FontAwesome Icon => FontAwesome.fa_question_circle;
@@ -45,16 +39,5 @@ namespace osu.Game.Modes
         public abstract string Description { get; }
 
         public abstract IEnumerable<KeyCounter> CreateGameplayKeys();
-
-        public static Ruleset GetRuleset(PlayMode mode)
-        {
-            Type type;
-
-            if (!available_rulesets.TryGetValue(mode, out type))
-                return null;
-
-            return Activator.CreateInstance(type) as Ruleset;
-        }
-
     }
 }

osu.Game/Modes/RulesetCollection.cs

@@ -0,0 +1,41 @@
+// Copyright (c) 2007-2017 ppy Pty Ltd <contact@ppy.sh>.
+// Licensed under the MIT Licence - https://raw.githubusercontent.com/ppy/osu/master/LICENCE
+
+using System;
+using System.Collections.Concurrent;
+using System.Collections.Generic;
+
+namespace osu.Game.Modes
+{
+    public static class RulesetCollection
+    {
+        private static readonly ConcurrentDictionary<int, Ruleset> available_rulesets = new ConcurrentDictionary<int, Ruleset>();
+
+        public static void Register(Type type)
+        {
+            Ruleset ruleset = Activator.CreateInstance(type) as Ruleset;
+
+            if (ruleset == null)
+                return;
+
+            available_rulesets.TryAdd(available_rulesets.Count, ruleset);
+        }
+
+        public static Ruleset GetRuleset(PlayMode playMode)
+        {
+            return GetRuleset((int)playMode);
+        }
+
+        public static Ruleset GetRuleset(int rulesetId)
+        {
+            Ruleset ruleset;
+            
+            if (!available_rulesets.TryGetValue(rulesetId, out ruleset))
+                throw new InvalidOperationException($"Ruleset id {rulesetId} doesn't exist. How did you trigger this?");
+
+            return ruleset;
+        }
+
+        public static IEnumerable<Ruleset> AllRulesets => available_rulesets.Values;
+    }
+}

osu.Game/Overlays/Mods/ModSelectOverlay.cs

@@ -41,7 +41,7 @@ namespace osu.Game.Overlays.Mods
 
         private void modeChanged(PlayMode newMode)
         {
-            var ruleset = Ruleset.GetRuleset(newMode);
+            var ruleset = RulesetCollection.GetRuleset(newMode);
             foreach (ModSection section in modSectionsContainer.Children)
                 section.Buttons = ruleset.GetModsFor(section.ModType).Select(m => new ModButton(m)).ToArray();
             refreshSelectedMods();

osu.Game/Overlays/Options/OptionsFooter.cs

@@ -30,7 +30,7 @@ namespace osu.Game.Overlays.Options
             foreach (PlayMode m in Enum.GetValues(typeof(PlayMode)))
                 modes.Add(new TextAwesome
                 {
-                    Icon = Ruleset.GetRuleset(m).Icon,
+                    Icon = RulesetCollection.GetRuleset(m).Icon,
                     Colour = Color4.Gray,
                     TextSize = 20
                 });

osu.Game/Screens/Play/Player.cs

@@ -109,7 +109,7 @@ namespace osu.Game.Screens.Play
                 sourceClock.Reset();
             });
 
-            ruleset = Ruleset.GetRuleset(Beatmap.PlayMode);
+            ruleset = RulesetCollection.GetRuleset(Beatmap.PlayMode);
             HitRenderer = ruleset.CreateHitRendererWith(Beatmap);
 
             scoreProcessor = HitRenderer.CreateScoreProcessor();

osu.Game/Screens/Select/BeatmapInfoWedge.cs

@@ -100,7 +100,7 @@ namespace osu.Game.Screens.Select
                 }));
 
                 //get statistics fromt he current ruleset.
-                labels.AddRange(Ruleset.GetRuleset(beatmap.BeatmapInfo.Mode).GetBeatmapStatistics(beatmap).Select(s => new InfoLabel(s)));
+                labels.AddRange(RulesetCollection.GetRuleset(beatmap.BeatmapInfo.Mode).GetBeatmapStatistics(beatmap).Select(s => new InfoLabel(s)));
             }
 
             AlwaysPresent = true;

osu.Game/osu.Game.csproj

@@ -131,6 +131,7 @@
     <Compile Include="Modes\Objects\Legacy\LegacyHitObjectType.cs" />
     <Compile Include="Modes\Replays\ReplayButtonState.cs" />
     <Compile Include="Modes\Replays\ReplayFrame.cs" />
+    <Compile Include="Modes\RulesetCollection.cs" />
     <Compile Include="Modes\Scoring\Score.cs" />
     <Compile Include="Modes\Scoring\ScoreProcessor.cs" />
     <Compile Include="Modes\UI\HealthDisplay.cs" />