Once.h

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/** @noop License Comment
 *  @file
 *  @copyright
 *  This Source Code is subject to the terms of the Mozilla Public License, v2.0.
 *  If a copy of the MPL was not distributed with this file You can obtain one at
 *  https://mozilla.org/MPL/2.0/
 *  
 *  @author David Mórász
 *  @date 2025
 */
 
#pragma once
 
#include "CoreMinimal.h"
 
namespace Mcro::Once
{
    /**
     *  @brief 
     *  Used for lambdas which supposed to run only once. The first time it is converted to bool it returns true
     *  but every other times it will return false.
     *  
     *  Usage:
     *  @code
     *  using namespace BaseUtils;
     *  SomeEvent.AddLambda([once = FOnce()]
     *  {
     *      // Just use it inside a condition
     *      if (once) { ... }
     *      
     *      // exploiting short-circuit:
     *      if (MyCondition && once) { ... }
     *  
     *      // but this will not produce the expected result:
     *      if (once && MyCondition) { ... } // BAD
     *  }
     *  @endcode
     */
    struct FOnce
    {
    private:
        bool bIsValid = true;
        
    public:
        FORCEINLINE FOnce() {}
        FORCEINLINE FOnce(const FOnce& from) : bIsValid(from.bIsValid) {}
        FORCEINLINE FOnce(FOnce&& from) noexcept
        {
            from.bIsValid = false;
        }
        FORCEINLINE FOnce(FOnce&& from) noexcept {…}
 
        FORCEINLINE operator bool()
        {
            const bool result = bIsValid;
            bIsValid = false;
            return result;
        }
        FORCEINLINE operator bool() {…}
 
        FORCEINLINE bool IsTriggered() const
        {
            return !bIsValid;
        }
        FORCEINLINE bool IsTriggered() const {…}
 
        FORCEINLINE void Reset()
        {
            bIsValid = true;
        }
        FORCEINLINE void Reset() {…}
    };
    struct FOnce {…};
}
namespace Mcro::Once {…}