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Lidarr/Marr.Data/LazyLoaded.cs

129 lines
3.2 KiB

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Data.Common;
namespace Marr.Data
{
public interface ILazyLoaded : ICloneable
{
void Prepare(Func<IDataMapper> dbCreator, object parent);
void LazyLoad();
}
/// <summary>
/// Allows a field to be lazy loaded.
/// </summary>
/// <typeparam name="TChild"></typeparam>
public class LazyLoaded<TChild> : ILazyLoaded
{
protected TChild _child;
protected bool _isLoaded;
public LazyLoaded()
{
}
public LazyLoaded(TChild val)
{
_child = val;
_isLoaded = true;
}
public TChild Value
{
get
{
LazyLoad();
return _child;
}
}
public virtual void Prepare(Func<IDataMapper> dbCreator, object parent)
{ }
public virtual void LazyLoad()
{ }
public static implicit operator LazyLoaded<TChild>(TChild val)
{
return new LazyLoaded<TChild>(val);
}
public static implicit operator TChild(LazyLoaded<TChild> lazy)
{
return lazy.Value;
}
public object Clone()
{
return this.MemberwiseClone();
}
}
/// <summary>
/// This is the lazy loading proxy.
/// </summary>
/// <typeparam name="TParent">The parent entity that contains the lazy loaded entity.</typeparam>
/// <typeparam name="TChild">The child entity that is being lazy loaded.</typeparam>
internal class LazyLoaded<TParent, TChild> : LazyLoaded<TChild>
{
private TParent _parent;
private Func<IDataMapper, TParent, TChild> _query;
private Func<IDataMapper> _dbCreator;
internal LazyLoaded(Func<IDataMapper, TParent, TChild> query)
: base()
{
_query = query;
}
public LazyLoaded(TChild val)
: base(val)
{
_child = val;
_isLoaded = true;
}
/// <summary>
/// The second part of the initialization happens when the entity is being built.
/// </summary>
/// <param name="dbCreator">Knows how to instantiate a new IDataMapper.</param>
/// <param name="parent">The parent entity.</param>
public override void Prepare(Func<IDataMapper> dbCreator, object parent)
{
_dbCreator = dbCreator;
_parent = (TParent)parent;
}
public bool IsLoaded
{
get { return _isLoaded; }
}
public override void LazyLoad()
{
if (!_isLoaded)
{
using (IDataMapper db = _dbCreator())
{
_child = _query(db, _parent);
_isLoaded = true;
}
}
}
public static implicit operator LazyLoaded<TParent, TChild>(TChild val)
{
return new LazyLoaded<TParent, TChild>(val);
}
public static implicit operator TChild(LazyLoaded<TParent, TChild> lazy)
{
return lazy.Value;
}
}
}