# Upgrade smart contracts 2: delegatecall

**Published by:** [Hicss](https://paragraph.com/@freesuton/)
**Published on:** 2022-01-18
**URL:** https://paragraph.com/@freesuton/upgrade-smart-contracts-2-delegatecall

## Content

Delegatecalldelegatecall is a low level function similar to call.When contract A executes delegatecall to contract B, B's code is executed with contract A's storage, msg.sender and msg.value.Common Call: When we call B's function from A, B's code is executed with contract B's storage. x in A is still 0.Delegatecall: When we call B's function from A, B's code is executed with contract A's storage. x in A will be 1.So we get a method to update the contract.We can just change the address in A to call different contracts between B and B2 by using delegatecall.Example Code:

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