FilterCollection.h

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// Copyright Epic Games, Inc. All Rights Reserved.
 
#pragma once
 
#include "CoreTypes.h"
#include "Containers/Array.h"
#include "Templates/SharedPointer.h"
#include "Delegates/Delegate.h"
#include "Misc/IFilter.h"
 
/**
 *  A simple collection of Filters, with additional Filter specific functionality.
 */
template< typename ItemType >
class TFilterCollection
    : public TSharedFromThis< TFilterCollection< ItemType > >
{
public:
 
    /** 
     * TFilterCollection destructor. Unregisters from all child filter changed delegates.
     */
    ~TFilterCollection()
    {
        for( auto Iterator = ChildFilters.CreateIterator(); Iterator; ++Iterator )
        {
            const TSharedPtr< IFilter< ItemType > >& Filter = *Iterator;
 
            if ( Filter.IsValid() )
            {
                Filter->OnChanged().RemoveAll( this );
            }
        }
    }
 
    /**
     *  Adds the specified Filter to the collection
     *
     *  @param  Filter  The filter object to add to the collection
     *  @return         The index in the collection at which the filter was added
     */
    int32 Add( const TSharedPtr< IFilter< ItemType > >& Filter )
    {
        int32 ExistingIdx;
        if ( ChildFilters.Find(Filter, ExistingIdx) )
        {
            // The filter already exists, don't add a new one but return the index where it was found.
            return ExistingIdx;
        }
 
        if( Filter.IsValid() )
        {
            Filter->OnChanged().AddSP( this, &TFilterCollection::OnChildFilterChanged );
        }
 
        int32 Result = ChildFilters.Add( Filter );
        ChangedEvent.Broadcast();
 
        return Result;
    }
 
    /** 
     *  Removes as many instances of the specified Filter as there are in the collection
     *  
     *  @param  Filter  The filter object to remove from the collection
     *  @return         The number of Filters removed from the collection
     */
    int32 Remove( const TSharedPtr< IFilter< ItemType > >& Filter )
    {
        if (Filter.IsValid())
        {
            Filter->OnChanged().RemoveAll(this);
        }
 
        int32 Result = ChildFilters.Remove( Filter );
 
        // Don't broadcast if the collection didn't change
        if (Result > 0)
        {
            ChangedEvent.Broadcast();
        }
 
        return Result;
    }
 
    /** 
     *  Gets the filter at the specified index
     *  
     *  @param  Index   The index of the requested filter in the ChildFilters array.
     *  @return         Filter at the specified index
     */
    TSharedPtr< IFilter< ItemType > > GetFilterAtIndex( int32 Index )
    {
        return ChildFilters[Index];
    }
 
    /** Returns the number of Filters in the collection */
    FORCEINLINE int32 Num() const
    {
        return ChildFilters.Num();
    }
 
    /** 
     *  Returns whether the specified Item passes all of the filters in the collection
     *
     *  @param  InItem  The Item to check against all child filter restrictions
     *  @return         Whether the Item passed all child filter restrictions
     */
    bool PassesAllFilters( ItemType InItem ) const
    {
        for (int Index = 0; Index < ChildFilters.Num(); Index++)
        {
            if( !ChildFilters[Index]->PassesFilter( InItem ) )
            {
                return false;
            }
        }
 
        return true;
    }
 
    /** Broadcasts anytime the restrictions of any of the child Filters change */
    DECLARE_EVENT( TFilterCollection<ItemType>, FChangedEvent );
    FChangedEvent& OnChanged() { return ChangedEvent; }
 
protected:
 
    /** 
     *  Called when a child Filter restrictions change and broadcasts the FilterChanged delegate
     *  for the collection
     */
    void OnChildFilterChanged()
    {
        ChangedEvent.Broadcast();
    }
 
    /** The array of child filters */
    TArray< TSharedPtr< IFilter< ItemType > > > ChildFilters;
 
    /** Fires whenever any filter in the collection changes */
    FChangedEvent ChangedEvent;
};