How to check if data populate in mapping and how to get and display the data?(SOLIDITY)

Question

How to check if data populates in mapping and how to get the value and display for checking?

     address[] public players;
   address public owner;
    struct Bet {
      uint256 amountBet;
      uint16 matchSelected;
      uint16 resultSelected;
    //   address[] players;
   }
   struct Player {
      uint256 amountBet;
      uint16 matchSelected;
      uint16 resultSelected;
      uint numFunders;
      mapping (uint => Bet) Bets;
   }
   mapping(uint16 => bool) matchBettingActive;

   mapping(address => Player) public playerInfo;

function for bet:

function bet(uint16 _matchSelected, uint16 _resultSelected) public payable {
  
  Player storage c = playerInfo[_matchSelected];
  
  require(matchBettingActive[_matchSelected], "Betting: match voting is disabled");
  //Check if the player already exist
  require(!checkIfPlayerExists(msg.sender, _matchSelected));

  //Check if the value sended by the player is higher than the min value
  require(msg.value >= minimumBet);
  
  //Set the player informations : amount of the bet, match and result selected
  playerInfo[msg.sender].amountBet = msg.value;
  playerInfo[msg.sender].matchSelected = _matchSelected;
  playerInfo[msg.sender].resultSelected = _resultSelected;
  c.Bets[c.numFunders++] = Bet({ amountBet:msg.value,matchSelected: _matchSelected,resultSelected: _resultSelected});
  
  //Add the address of the player to the players array
  players.push(msg.sender);

  //Finally increment the stakes of the team selected with the player bet
  if ( _resultSelected == 1){
      totalBetHome[_matchSelected] += msg.value;
  }
  else if( _resultSelected == 2){
      totalBetAway[_matchSelected] += msg.value;
  }
  else{
      totalBetDraw[_matchSelected] += msg.value;
  }

}

Answer 1

You can call the mapping variable with the correct Id and the check if an attribute of the struct you get is different than their "Zero" value. you can chose an attribute that you know is always different than "Zero" like numFunders.

you can do the following :

if(playerInfo[anAddress].numFunders > 0){
    // this means that the slot with the anAddress is populated. 
    // you can get the data the same way too.
}

here is an example of accessing the struct data inside the mapping :

uint256 amountBet = playerInfo[address].amountBet;

uint16 matchSelected = playerInfor[address].matchSelected;