Questions tagged [smart-contract]

Anything related to decentralized application (dApp) development, concepts, and possibilities with smart contracts, or technical questions for the development of smart contracts.

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check (within smart contract) if an account is a proxy

How can I verify within a smart contract that an account is a proxy? I know that there is a function is_account, which verifies that a name is an existing account. Is there a way to check if an ...
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How can i burn the tokens i create with eosio.token

I want to burn the tokens i created for some reasons, I found the method "retire" in eosio.token. But, this method only change the supply of the token, the maximum supply is still the same as it is ...
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How to pass a map into an action

I'm trying to pass a map into action, but there is serialization error: Error: expected object containing data: undefined There is a function signature: void init(uint64_t id, const map<uint8_t, ...
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`env.is_feature_activated` error when set contract

I'm trying to set up my eos enviroment. When I post the system contracts I get this error msg: Error 3070000: WASM Exception Error Details: env.is_feature_activated unresolveable enviroment: ubuntu ...
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Is it possible to set up a smart contract with multiple .cpp and .hpp files?

If we want to make our smart contract code modular, and keep each class, contract, and table in its own file, is it possible to do this, and if so, how?
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Can smart contract trigger some action on specified timestamp and change certain account balances?

Imagine I have a poll with specified timestamp for the end. At that point in time votes should be tallied and voters token balances should be adjusted in both directions (increase and decrease). How ...
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what does the same_payer mean in eosio contract?

user_stakes.modify(sk,same_payer,[&](auto &s){ The variable same_payer confused me sometime, so, what does the same_payer mean in eosio contract ?
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Make a transfer from contract code on behalf of user [duplicate]

Installed: eosio: 1.7.3; eosio.cdt: 1.6.1 Implemented and locally deployed: sample market contract and eosio.token contract. In order to make an inline transfer from market contract in behalf of a ...
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Hide information in the blockchain

Lets say I want to create a player vs player game with a battlefield and moving armies, the movement and data about the armies and where is it going is put on the blockchain. My question is how to ...
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assertion failure with message: no balance object found

This error message occurs when trying to do a transfer: assertion failure with message: no balance object found What causes it and how can it be avoided?
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Unable to publish to Kylin

I have been developing against a local node, for which I created a key-pair. Now that it's time to publish to the testnet, I've imported said private key into Scatter and linked it to the account to ...
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no member named 'check' in namespace 'eosio'

I am trying to build a contract and receiving this error: In file included from /usr/opt/eosio.cdt/1.6.1/bin/../include/eosiolib/contracts/eosio/system.hpp:6:[0K /usr/opt/eosio.cdt/1.6.1/bin/../...
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How to get a contract to accept tokens as payment

I keep getting the following error: transaction declares authority '{"actor":"test2","permission":"active"}', but does not have signatures for it under a provided delay of 0 ms, provided permissions [...
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Is there a way to issue tokens infinitely?

I want to design a system where token supply can grow infinitely. Is it possible not to fix total supply at the token creation moment?
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Transfer tokens inside a smart contract from an account to another account

I need to write a simple function that would send tokens using a different account action. Exactly the same situation as in these questions: one and two But I have to use not eosio.token contract but ...
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What exactly the merkle function is returning?

In the below file, https://github.com/EOSIO/eos/blob/v1.7.4/libraries/chain/merkle.cpp, what do ids.front() mean?; what exactly this function Merkle is returning? Could you please explain what this ...
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What is the meaning of "scope" in a Smart Contract?

Since I have read the tutorial. I don't understanding the following: Note that scopes are used to logically separate tables within a multi-index (see the eosio.token contract multi-index for an ...
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Can not find `eosio/eosio.hpp` while compiling with eosio-cpp

I used the documentation provided by EOSI. I made all the required installation as suggested in the docs. While writing the hello world contract, I face this issue when running the following command ...
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How to debug eosio::on_notify("eosio.token::transfer") actions?

I'm working on a contract that will run an action when receiving tokens. The following code does not run when the account receives EOS or JUNGLE tokens on the Jungle Testnet. #include "./test.hpp" .....
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How to delete record on EOS if I forget table structure

I issue an EOS token for fun half a year ago and I'm planning to release my EOS ram recently. The problem is that I forget the table structure I made before and I overwrite the contract and there is ...
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Can I use Timers?

I know that there's no timer in other smart contracts and even this is not possible in regular blockchains. But, EOS uses C++, and they already did lots stuffs which makes smart contracts more usable. ...
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eosio-cpp command not found error?

When I am trying to run hello world smart contract using a command eosio-cpp -abigen -o hello.wasm hello.cpp shown an error eosio-cpp: command not found?
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Ico smart contract update

I would like to update this code, because it is CDT 1.2. I would like to update for CDT 1.5 or CDT 1.6. What do I need to change? #include <eosiolib/eosio.hpp> #include <eosiolib/currency....
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Contract compilation fails during elemental battles tutorial

I have followed the elemental battles tutorial until lesson 2 step 4, and at the end of it, the tutorial instructs to compile the existing code with eosio-cpp -o destination.abi source.cpp -abigen (...
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EOS Token contract audit issue

My token contract was done by a third party vendor that did not share source code of the token contract with me. Can you help me on how to find the code, so that I can submit it to you for audit ...
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Why is [[eosio::on_notify("eosio.token::transfer")]] not working?

Network: kylin testnet. I transferred eos to this contract, but it the "deposit" function was not called. What do I miss?
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Acting on upon a receipt of a token, using v1.6 c++ libraries

Let's say I wanted to act upon receipt of a token and/or a message to a smart contract. Previous versions of EOS used the apply function to do this, however as of v1.6 things have changed to pure cpp ...
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Time point to string

I am currently trying to get the current time using time_point_sec(now()); Does someone know how to convert that to a std::string?
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Using find on multi index table

I have a table defined as the following: struct [[ eosio::table, eosio::contract("voting") ]] identity { uint64_t key; key256 identityHash; time_point_sec createdAt; uint64_t ...
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Get symbol & contract from asset

I currently have an asset property that stores a value, i.e. 100 EOS which could also be another token like 100 TLOS. Is there a way to extract the symbol and possibly the token contract from that ...
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What are the advantages and disadvantages of using multiple smartcontracts?

I have noticed many EOS contract programmers choose to have a token contract and a seperate smart contract for other things to do with those tokens. What are the advantages and disadvantages to this ...
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read datastream of length 29 over by -4

enum house_status: uint64_t { NEW = 10, FULL = 20, ONGOING = 30, OVER = 40 }; struct [[eosio::table, eosio::contract("game")]] house{ uint64_t id; uint64_t owner_player_id; ...
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Serialization Error Processing WASM while following hello.cpp tutorial

I am following along the tutorial on the EOS website at https://developers.eos.io/eosio-home/docs/your-first-contract At the first smart contract development section, I cannot manage to publish the ...
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How do I confirm that the person sending an action is the same as a user in the parameter?

Specific example from a contract: ... void hi(name user){ // verification here, require_auth(user)? print(user); } ... I've tried require_auth(user) but that seems to always fail unless the user ...
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Is there a way to call a multisig approval programmatically from within a contract?

Following scenario: There's an action which requires 3 signatures - two are 'normal accounts' and the third one is like 'system or robot', which does some verifications from within the smart contract....
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How is memory aligned in the EOSIO smart contract consensus memory?

Are there any memory savings if I declare a table record that has, say, a 64-bit integer (occupies 8 bytes) and a 16-bit integer (occupies 2 bytes)? Or is it aligned at 64 bits and said record would ...
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3 votes
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Ricardian Contract

Does eosio also sign the transaction with the ricardian contract of user consent and/or how does the application proove that a party agreed on said ricardian contract? I have integrated the ricardian ...
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How do I access a contract class variable from an extern “C” function "void apply()"?

In some scenarios, It's convenient to configure the conditions for monitoring some certain transactions by using this method extern "C" { void apply(uint64_t receiver, uint64_t code, uint64_t ...
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Can I deploy a contract from within a contract? [duplicate]

We can create accounts from contract code: https://github.com/angelol/smart_account_creator and we can query things about accounts: https://github.com/nsjames/Account-Has-Code is there a way to ...
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Is it possible to create new contract from another?

Ethereum has a opportunity to create new contract from another. Does eosio has the same? I found a code with new account creation, but I didn't find nothing about setting code and abi from contract.
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Is it possible to lock publish contract with set permission?

Is it possible to setup a lock (multisig) for the command cleos set contract ? in order to request one or more signatures to deploy a contract ? cleos set action permission eosio eosio set ...
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2 votes
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CPU-Usage Optimization

I'm trying to figure out how to optimize one of my smart contracts for less billed CPU-usage. There are typically different methods to optimize performance of algorithms but I'm not clear about if a ...
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2 votes
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Why does using available_primary_key() as scope for a table result in this behaviour?

Scenario: Two tables, each using uint64_t as a primary key Table A rows need to reference rows in Table B Why? Relational database data duplication reasoning etc etc Both table's primary keys are ...
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1 vote
2 answers
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Why actions can't have return values?

I can't understand why actions can't return values. A simple use case is for adding records in multi_index. I need to return the primary key to link that to my off-chain data.
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on_notify not being fired on local or jungle testnet

I'm using the following contract on both my local and jungle testnets, the on_notify methods are not being fired. Everything appears to be in order, I'm hoping I've missed something obvious. I ...
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Duplicate symbol WASM compilation error when using header/hpp for contract

I'm looking to use a hpp file as an interface for multiple contracts. I've created a test contract and receiving a WASM compilation error. I based the test contract on the format used by eosio.token....
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Is there a library for encryption/decryption in EOS? [duplicate]

I want to perform some encryption on a given message, so I am wondering if there is a library that I can use in EOS? And I have checked the post Cryptographic Operations in Smart Contracts?, but the ...
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Smart contract - find on two columns

I am currently writing a blog PoC on EOS. I would like the ability to delete a post. Now deleting by the ID alone is simple, I have it implemented as follows: whisper::post_index posts(_code, _code....
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Stake EOS and then unstake

Is there any documentation on staking or unstaking EOS using smart contracts? I basically want to provide an escrow service where the seller needs to stake the value of the item and the buyer stakes ...
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No tables in abi file

I am trying to write a smart contract but for some reason my tables aren't being added to the abi file and therefore aren't being added to the blockchain. My code is as follows. Am I possibly ...
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