Learn Solidity (0.5) - Delegatecall

[@DaBossLewis]

Great video. You explained it very well. I have read about delegate call a few times, but this video really helped make the knowledge useful. Thanks :)

[@coinymous]

awesome , best channel for solidity I've seen 😍

[@salem232]

😍👍 super video explaining the content!!! Classic diagram with animation made very easy to grasp !! Thank you!!

[@benparish6772]

Great explanation. Easy to understand.

[@aryastark4064]

thanks for explaining all these very easily . that solidity document was driving me crazy

[@vanvantsyan]

awesome explanation!

[@SingleWingAcademy]

Great video. Helped me beat the level on ethernaut lol

[@edwassermann8368]

excellent. that was an important puzzle piece for me.

[@apoorvlathey5421]

This video was so helpful. Thanks!

[@TjSpoonManJacques]

Great video - I really appreciate you!

[@kb8341]

Best explanation ever!

[@startat3098]

You are the best as always!

[@rameezshuhaib6456]

Thanks for this awesome video! This was something I was searching for :)
But I have a doubt Wouldn’t this have any security issue? Since I can run any custom code and update the actual storage. Is there a way to allow only trusted upgraded contracts created by the owner?

[@smartcontractprogrammer]

Yes there are hacks done exploiting delegatecall. You will have to write authorization code for trusted upgrade

[@gabrielnastari8513]

address admin_address;
// only run in deploy
constructor(){
admin_address = admin_address;
}
function something(){
require( msg.sender == admin_address, "Dont authorized");
delegatecall()
}

[@smartcontractprogrammer]

@@gabrielnastari8513
constructor() { admin_address = msg.sender ; }

[@gabrielnastari8513]

@@smartcontractprogrammer right, lol! i wrote twice ! You correct admin_address =msg.sender !

[@gabrielnastari8513]

@@smartcontractprogrammer Thanks , you are awesome man!

[@japaroski]

You are the best!

[@كيفتصنعللاطفال]

Thanks for the great tutorial. I deployed your example using Javascript VM. It works.
I deployed it using Ropsten testnet. It does not work.
Can you please help me to run it on a testnet.
Thank you

[@smartcontractprogrammer]

Deploy all relevant contracts on Ropsten. Make sure the addresses are correct

[@كيفتصنعللاطفال]

@@smartcontractprogrammer I ran the same code on Ropsten again and I am sure that the addresses are correct. It still does not work. Have you tried it yourself?
I even modified your code as below. I give the input 2. When I run it on JavaScript VM the result is 8. When I run it on Ropsten the result is 4. Different results for the same code. Please try the code below yourself
/*first file*/
pragma solidity ^0.7.6;
abstract contract B {
function setVars(uint _num) public payable returns(uint) {}
}
contract A {
uint public num=1;
uint x=1;
function setVars(address _contract, uint _num) public payable {
// A's storage is set, B is not modified.

num = B(_contract).setVars(_num);
(bool success, bytes memory data) = _contract.delegatecall(abi.encodeWithSignature("setVars(uint256)", num));
}
}
/*second file*/
pragma solidity ^0.7.6;
contract B {
// NOTE: storage layout must be the same as contract A
uint public num;
address public sender;
uint public value;
uint x=1;
function setVars(uint _num) public payable returns(uint) {
num = 2*_num;
sender = msg.sender;
value = msg.value;
return num;
}
}
Thank you and I appreciate your kind help to me

[@كيفتصنعللاطفال]

can you help me please :)

[@福瑞黃]

Very Good and no one can do better than you ! Well, If I don't other contracts to call or delegatecall the functions of my contract, what should I do? Please advise, Thanks!

[@MrCoreyTexas]

I'm wondering, when was delegatecall introduced into the EVM? Was it there from the beginning, or did they add it later when they figured out that they'd need a way to upgrade contracts?

[@smartcontractprogrammer]

It was there from long time ago. I don't know when

[@rattle_]

So the first contract works like a proxy.

[@smartcontractprogrammer]

Exactly! Upgradable contracts use this to separate storage and code

[@jordixboy]

Good explanation, what happens if you do a delegate call, the contract calls the second contract, but the first contract doesnt have that state variables defined, I assume the call would fail?

[@smartcontractprogrammer]

it might fail
it might be an entry to hack the contract

[@malawad]

super helpful , thanks a lot

[@jagadeeshgajula4014]

very cool

[@MrCoreyTexas]

very interesting, programming was getting kind of dull for me over many decades (nothing new under the sun as it were) until i discovered crypto currency

[@neeble9575]

You are the best!