Say we have:

contract TestFooContract{
//bunch of stuff and state

Does this mean that there is only 1 "TestFooContract"? Or can I instantiate 10 of them? What if I want multiple of these contracts? In OOP terms, is a contract thought of as a class? Or perhaps just a singleton object?

  • My understanding is that you can either construct/deploy a contract with bytecode (and receive an address) or with an address (of an already deployed contract) and receive a new address? Is that right?
    – Rich
    Apr 7, 2018 at 4:03

4 Answers 4


Addresses are generated independently from the code inside them. So yes, you can generate ten different addresses all with the same code.

  • If you extend an existing contract in solidity, do you'd still reuse to compiled code as well?
    – Gerbrand
    Apr 21, 2016 at 12:10

A particular contract is like a class, and many copies of it can be made, and other contracts can inherit from it.

Each contract is defined by an address. New contracts can be produced with MyContract myNewContract = new MyContract(arg1,arg2,...)

By default, the last contract defined in a Solidity file is instantiated, and others can be instantiated from within the contract.


Just like code can be in source form, or converted/compiled to executable form, the same thing applies to contracts.

From source code, many copies of the executable form can be generated.

In source code form, a contract in Solidity is like a class in OOP terms: it can be instantiated many times, and can be inherited from.

Making a contract executable, usually involves 2 steps:

  1. converting the source to Ethereum Virtual Machine (EVM) bytecode
  2. deploying the EVM to an Ethereum blockchain

The same contract source code or EVM can be deployed to a blockchain many times. Each instance of a deployed contract has a unique address.

  • The same contract can be deployed multiple times even if no source code is available. The deployment can be done by observing the ABI and binary code submission on the blockchain network and then replicating it.
    – dionyziz
    May 23, 2020 at 7:43

@Joris: I understand that your question relates to understanding the concept of a Blockchain in relation to Smart Contracts at "runtime". A good question that kept me busy for a while.

There is no such thing as a Singleton. Singletons are a concept of other programming languages with a local address space. A Blockchain is distributed.

As Tjaden said, each contract is defined by an address. Lets call it an instance for the sake of OO-language concepts.

Each time you change the state of that particular instance, your winning miner will put a newer copy in the newest Block. You always interact with the topmost entry that is represented by the address. Older copies stay where they are but ignored. Thus you have a "chain" of serialized entries but only one contract instance.

You are free to create new contract instancies of the same type. That instance will have another address.

Once a Block has been mined, it is immutable. Your first and any other instance will be permafrosted forever by your miner. You interact with the topmost. Any new state goes on top.

  • "will put a newer copy in the newest Block" Copy what? The full smarcontract? I don't think so. Are not only the states copied? Jun 15, 2018 at 16:06

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.