C++ vector - find element

Question

C++ vector - find element

Markus Freitag 3,791

Hello,

struct PanelData  
	{  
		// **   
		CString Price;  
		CString IdentNo;  
  
		bool    PanelReported;  
	  
	};  
	  
	vector<PanelData>	  m_dequePanelData;  
	  
  
std::vector<PanelData>::iterator it;  
it = find(m_dequePanelData.begin(), m_dequePanelData.end(), it->PanelReported = true);  
  
int pos = it - m_dequePanelData.begin();

I am using a vector and want to find the PanelData,
where the first variable PanelReported is true.

I use a vector and want to find the panel data where the variables PanelReported are true.

How can I achieve this?

So once targeted the first hit like FirstOrDefault()
Furthermore a list with the value true.

Current error message.
Why and how can I solve it? Thanks.

Barry Schwarz 3,746 Reputation points

2022-09-30T19:38:51.46+00:00

The third parameter of the find function must have the same type as the elements of the vector. In your case, the elements have type struct but your parameter has type bool.

The find_if function allows to specify a comparison function that accepts a argument with the same type as the vector elements and performs whatever testing you desire. See https://cplusplus.com/reference/algorithm/find_if/ for description and an easy example.
Markus Freitag 3,791 Reputation points

2022-10-01T10:33:24.447+00:00

OK, thanks!

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Barry Schwarz 3,746 Reputation points

2022-09-30T19:38:51.46+00:00

The third parameter of the find function must have the same type as the elements of the vector. In your case, the elements have type struct but your parameter has type bool.

The find_if function allows to specify a comparison function that accepts a argument with the same type as the vector elements and performs whatever testing you desire. See https://cplusplus.com/reference/algorithm/find_if/ for description and an easy example.
Markus Freitag 3,791 Reputation points

2022-10-01T10:33:24.447+00:00

OK, thanks!

Answer 1

Viorel 122.5K

Try this code:

it = std::find_if( m_dequePanelData.begin( ), m_dequePanelData.end( ), []( const PanelData& d ) { return d.PanelReported; } );  
if( it == m_dequePanelData.end( ) )  
{  
    // not found  
    // . . .  
}  
else  
{  
    // found  
    int pos = it - m_dequePanelData.begin( );  
    // . . .  
}

If you want to examine all of items, you can use a loop instead of find_if.

Markus Freitag 3,791 Reputation points

2022-09-30T18:46:33.17+00:00

If you want to examine all of items, you can use a loop instead of find_if.

Thank you for your prompt reply. Can you show it with the loop?

Viorel 122.5K

For example:

for( const PanelData& d : m_dequePanelData )  
{  
    if( !d.PanelReported ) continue;  
  
    // d.PanelReported is true  
    . . .  
  
}

In C++ 20 (which can be specified in Project Properties), you can try something like this:

#include <ranges>  
. . .  
for( const PanelData& d : m_dequePanelData | std::views::filter( []( const PanelData& t ) { return t.PanelReported; } ))  
{  
    // d.PanelReported is true  
    . . .  
}

Markus Freitag 3,791 Reputation points

2022-10-01T10:33:50.793+00:00

Thanks for the sample!

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C++ vector - find element

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