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Comparers (#929)

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* Add entity equality comparers

* Fix namespace #whoops

* Add Message comparer.

* Add comment explaining the specialized implementation

* Remove specialized implementation, as per feedback
This commit is contained in:
Joe4evr
2018-01-11 03:31:43 +01:00
committed by Christopher F
parent 97397f3617
commit b5e7548651
1 changed files with 45 additions and 0 deletions
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45
src/Discord.Net.Core/Utils/Comparers.cs Normal file
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using System;
using System.Collections.Generic;
namespace Discord
{
public static class DiscordComparers
{
// TODO: simplify with '??=' slated for C# 8.0
public static IEqualityComparer<IUser> UserComparer => _userComparer ?? (_userComparer = new EntityEqualityComparer<IUser, ulong>());
public static IEqualityComparer<IGuild> GuildComparer => _guildComparer ?? (_guildComparer = new EntityEqualityComparer<IGuild, ulong>());
public static IEqualityComparer<IChannel> ChannelComparer => _channelComparer ?? (_channelComparer = new EntityEqualityComparer<IChannel, ulong>());
public static IEqualityComparer<IRole> RoleComparer => _roleComparer ?? (_roleComparer = new EntityEqualityComparer<IRole, ulong>());
public static IEqualityComparer<IMessage> MessageComparer => _messageComparer ?? (_messageComparer = new EntityEqualityComparer<IMessage, ulong>());
private static IEqualityComparer<IUser> _userComparer;
private static IEqualityComparer<IGuild> _guildComparer;
private static IEqualityComparer<IChannel> _channelComparer;
private static IEqualityComparer<IRole> _roleComparer;
private static IEqualityComparer<IMessage> _messageComparer;
private sealed class EntityEqualityComparer<TEntity, TId> : EqualityComparer<TEntity>
where TEntity : IEntity<TId>
where TId : IEquatable<TId>
{
public override bool Equals(TEntity x, TEntity y)
{
bool xNull = x == null;
bool yNull = y == null;
if (xNull && yNull)
return true;
if (xNull ^ yNull)
return false;
return x.Id.Equals(y.Id);
}
public override int GetHashCode(TEntity obj)
{
return obj?.Id.GetHashCode() ?? 0;
}
}
}
}