So far, we have implemented three of the main CRUD operations. Now it’s time to define the last, the DELETE operation, to deactivate or remove existing entries. To achieve that, we define the following removePlayer() method:

modifier onlyadmin(){
    require(msg.sender == admin);
     _;
}

function removePlayer(address _address) public onlyadmin returns (bool) {
    delete players[_address];
    return true;
}

removePlayer() will remove an element (player) at a specific index (address). Solidity provides the delete operator to reset deleted elements to the default value. In the mapping, the corresponding value to the specified key (address) will be set to zero, and the mapping structure will remain the same.

Moreover, we can apply delete to a given array member as Delete MyArray[3]. This implies that the value of MyArray[3] will equal zero without reducing the array length. If we want to physically remove the element with reindexing, we need to delete it and manually resize the array. Deleting elements in Solidity behaves like an update with the initial value for the type.

The equivalent SQL statement to the previous function would be DELETE from players where address=_address;.

You might be wondering about deleting the mapping as we do in SQL for a table: DROP TABLE players;

This is currently impossible for a mapping, but it's possible to delete a dynamic array or a structure.

One last thing to mention: in your CRUD contract, you can manage contract roles and permissions using modifiers. For example, we can define fixed roles and assign permissions based on specific attributes (owner, and player) to control access to specific functions (actions).

At this point, we have accomplished the goal of this first section. We have built our Cplayer contract following a CRUD pattern. Now, let's move on to building the Ctontine contract while creating an Itontine interface.