This is an example of the difference between "address.send()", "address.call.value()()" and "address.transfer()" in Solidity. If you like this example, then checkout my courses I do on Udemy (https://vomtom.at/tag/course/)

send_transfer_call.sol

pragma solidity ^0.4.13;

contract someContract {
    
    mapping(address => uint) balances;
    
    function deposit() payable {
        balances[msg.sender] += msg.value;
    }
    
    function withdrawVeryBad1(uint amount) {
        if(balances[msg.sender] >= amount) {
            msg.sender.send(amount);
            balances[msg.sender] -= amount;
        }
    }
    function withdrawVeryVeryBad2(uint amount) {
        if(balances[msg.sender] >= amount) {
            msg.sender.call.gas(2500000).value(amount)();
            balances[msg.sender] -= amount;
        }
    }
    function withdrawVeryVeryBad3(uint amount) {
        if(balances[msg.sender] >= amount) {
            if(msg.sender.call.gas(2500000).value(amount)()) {
                balances[msg.sender] -= amount;
            }
        }
    }
    
    function withdrawBad1(uint amount) {
        if(balances[msg.sender] >= amount) {
            if(msg.sender.send(amount)) {
                balances[msg.sender] -= amount;
            }
        }
    }
    function withdrawOkayish(uint amount) {
        if(balances[msg.sender] >= amount) {
            balances[msg.sender] -= amount;
            if(!msg.sender.send(amount)) {
               throw;
            }
        }
    }
    function withdrawBad2(uint amount) {
        if(balances[msg.sender] >= amount) {
            balances[msg.sender] -= amount;
            if(!msg.sender.call.gas(2500000).value(amount)()) {
               throw;
            }
        }
    }
    
    
    //OKAY FUNCTIONS
    
    function withdrawOK(uint amount) {
        if(balances[msg.sender] >= amount) {
            balances[msg.sender] -= amount;
            msg.sender.transfer(amount);
        }
    }
    
    //New Exception handling
    function withdrawGood(uint amount) {
        require(balances[msg.sender] >= amount);
        balances[msg.sender] -= amount;
        msg.sender.transfer(amount);
    }
}

Hey Tom,

Should not we should have some function to get or check the current balance of the account, so that we can check how much amount is remaining after the whole flow of deposit and withdraw.

It would be great if you could explain the problems with the 'bad' functions for those who are learning the language!

+1 to explaining

always call address.send(), address.call.value()() and address.transfer() at the very end of the function, or you will experience re-entry attack

@yyssjj33 I dont think address.call.value()() is a safe against re-entry attack. The other 2 have a gas limit but not call.value(). Unless you specify gas limit using gas().