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"
 
template< typename ItemType >
class TFilterCollection
    : public TSharedFromThis< TFilterCollection< ItemType > >
{
public:
 
    ~TFilterCollection()
    {
        for( auto Iterator = ChildFilters.CreateIterator(); Iterator; ++Iterator )
        {
            const TSharedPtr< IFilter< ItemType > >& Filter = *Iterator;
 
            if ( Filter.IsValid() )
            {
                Filter->OnChanged().RemoveAll( this );
            }
        }
    }
 
    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;
    }
    
    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;
    }
 
    TSharedPtr< IFilter< ItemType > > GetFilterAtIndex( int32 Index )
    {
        return ChildFilters[Index];
    }
 
    UE_FORCEINLINE_HINT int32 Num() const
    {
        return ChildFilters.Num();
    }
 
    bool PassesAllFilters( ItemType InItem ) const
    {
        for (int Index = 0; Index < ChildFilters.Num(); Index++)
        {
            if( !ChildFilters[Index]->PassesFilter( InItem ) )
            {
                return false;
            }
        }
 
        return true;
    }
 
    DECLARE_EVENT( TFilterCollection<ItemType>, FChangedEvent );
    FChangedEvent& OnChanged() { return ChangedEvent; }
 
protected:
 
    void OnChildFilterChanged()
    {
        ChangedEvent.Broadcast();
    }
 
    TArray< TSharedPtr< IFilter< ItemType > > > ChildFilters;
 
    FChangedEvent ChangedEvent;
};