fallback-functions-practice

pragma solidity ^0.8.2;

/* Describe Fallback functions
    - cannot have a name (anonymous)
    - does not take any inputs
    - does not return any outputs
    - must be declared as external
*/

contract FallBack {

event Log(uint gas);
    
    fallback () external payable {
        // not recommended to write much code in here - because the function will fail if it uses too much gas
        
        // invoke the send and transfer methods: we get 2300 gas which is enough to emit a log   
        // invoke the call method: we get all the gas 
        
        // special solidity function gasleft returns how much gas is left
        emit Log(gasleft());
    }
    
    function getBalance() public view returns(uint) {
        // return the stored balance of the contract 
        return address(this).balance;
    }
    
}


// new contract will send ether to Fallback contract which will triggger fallback functions 

contract SendToFallBack {
    
    function transferToFallBack(address payable _to) public payable {
        // send ether with the transfer method
        // automatically transfer will transfer 2300 gas amount 
        _to.transfer(msg.value);
    }
    
    
    function callFallBack(address payable _to) public payable {
        // send ether with the call method 
        (bool sent,) = _to.call{value:msg.value}('');
        require(sent, 'Failed to send!');
    }
    
}





// Exercise is to understand these contracts and write it out and explain the logic event Log(uint gas);
    
    fallback () external payable {
        // not recommended to write much code in here - because the function will fail if it uses too much gas
        
        // invoke the send and transfer methods: we get 2300 gas which is enough to emit a log   
        // invoke the call method: we get all the gas 
        
        // special solidity function gasleft returns how much gas is left
        emit Log(gasleft());
    }
    
    function getBalance() public view returns(uint) {
        // return the stored balance of the contract 
        return address(this).balance;
    }
    
}


// new contract will send ether to Fallback contract which will triggger fallback functions 

contract SendToFallBack {
    
    function transferToFallBack(address payable _to) public payable {
        // send ether with the transfer method
        // automatically transfer will transfer 2300 gas amount 
        _to.transfer(msg.value);
    }
    
    
    function callFallBack(address payable _to) public payable {
        // send ether with the call method 
        (bool sent,) = _to.call{value:msg.value}('');
        require(sent, 'Failed to send!');
    }
    
}

}