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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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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151 views

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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1answer
28 views

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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437 views

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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78 views

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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2answers
642 views

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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0answers
54 views

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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3answers
116 views

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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1answer
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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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1answer
119 views

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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2answers
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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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55 views

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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40 views

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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1answer
91 views

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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55 views

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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1answer
80 views

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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1answer
42 views

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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1answer
182 views

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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1answer
250 views

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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76 views

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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1answer
359 views

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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1answer
437 views

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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1answer
46 views

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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3answers
163 views

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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1answer
55 views

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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0answers
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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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1answer
51 views

Is there any API in EOS Smart Contract to decrypt message? [duplicate]

I would like to create a smart contract that would be able to decrypt some symmetrically encrypted message. Here is the scenario: Party "A" sends a message encrypted with key "123456" to ...
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1answer
233 views

Broadcast Smart Contract 'Hello World' error

I am going through the eos tutorial but I got stuck at the contract broadcast. When I compile the contract with eosio-cpp -o hello.wasm hello.cpp --abigen the console seems to get stuck and I have ...
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2answers
59 views

Transaction took too long while using std::shuffle

Get the error when I push a action on my contract on the local testnet: But if I remove this code from the action I called, there is no problem: class urng: Does anyone know what caused this?I just ...
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1answer
310 views

What could be the reason for 'Error 3050008: Abort Called'

I'm getting the following error without any further description. What could be the issue for that? I'm performing some binary arithmetics when calling this action, are there any known problems with ...
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2answers
1k views

How to use checksum256 secondary index to get table rows

Does anyone know the correct way to get table rows using checksum256 (fixed_bytes<32>) secondary index through the get_table_rows RPC API? I found a way using key256, but key256 is deprecated ...
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121 views

require_auth() not working as expected

I adapted the hello contract, expanding with require_auth() and added an additional account oliver that should be able to execute the action hashin on behalf of the contract owner doctest1. I adjusted ...
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2answers
998 views

How to get current time in different versions of EOSIO

Depending on which version of EOSIO you use, there are different options available for finding the current time. What are they?
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2answers
522 views

Make a transfer inline

I would like to send SYS token owned by the smart contract account to a third party account when anyone call a specific action. I have tried the following code but I am getting an error: [[eosio::...
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1answer
147 views

How do I set my smart-contract / account to “immutable”?

What's the correct cleos command to yield the active/owner permissions of a deployed contract to "eosio.code", exclusively?
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1answer
70 views

`cleos get table` not returning vector<string>

I declare a vector vector<string> data inside a contract. Contract Code: book.emplace(_self, [&](struct wname &a){ a.name = fa.pubaddress; a.namehash = ...
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1answer
242 views

How to convert a public key string to a eosio::publickey object inside a smart contract?

The smart contract takes a string as an input for the public key. I need to convert it into a public key object within the contract.
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3answers
367 views

Custom dispatcher new CDT

I'm having compilation issues when creating a custom dispatcher. I'm getting issues when calling EOSIO_DISPATCH. Is it related to changes in new CDT? class [[eosio::contract("mycontract")]] ...
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2answers
165 views

Multi_index issues

I'm getting a lot of errors related to multi_index after updating to the newest eosio.cdt. Here is part of my code related to hash. struct st_hash { capi_checksum256 hash; uint64_t expiration; ...
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1answer
67 views

Does EOSIO Have Native Contracts Built-Into Protocol Layer?

On the Bitshares site I read https://bitshares.org/technology/industrial-performance-scalability Based upon the lessons we learn from LMAX, we know that a virtual machine for a blockchain should be ...
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1answer
152 views

Issue while compiling smart contract - eosio.cdt

I have installed eosio.cdt in Ubuntu system by using commands from EOS Developers Portal wget https://github.com/EOSIO/eosio.cdt/releases/download/v1.4.1/eosio.cdt-1.4.1.x86_64.deb sudo apt install ./...
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2answers
104 views

What can prevent one from changing contract code?

I find one major characteristic of EOSIO is that the smart contract code is interchangeable, so that developers can easily fix any bugs or change its logic. But what if someone changes the code to ...
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cannot get latest state of table after modifying table in inline action

As shown with code below, I modify table in an inline action, and then want to get the latest data. But the data I get is not the latest. Why? void mycontract::myfunc() { action ( ...
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1answer
86 views

How to have real-time communication in dapp?

How would a real-time 1v1 game work on the EOS Blockchain? I've noticed that many of the games/gambling dapps on EOS are mostly player vs. blockchain, like EOSBet. Could I have real-time updates to ...
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2answers
149 views

Require authorization with conditions require_auth(name1 OR name2)

Is there any possibility to implement conditional require_auth(<condition>) or what is a good practice to make contract accept invocations from a set of predetermined accounts? Is there any ...
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1answer
53 views

Is there a way to prevent me spending tokens until an action is called?

I am creating a smart contract but came to a halt when writing the code. Is there a way, in a smart contract, to prevent me from spending tokens transferred to me by another user through the smart ...
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2answers
115 views

How to avoid cpu usage limits

Task Compute some fields for all table rows when action called contract::priceupdate(price) Input data: Table with 10000 rows Problem Cpu limit 30ms so i cant update whole table in 1 transaction ...
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1answer
124 views

Passing the action name having return type to EOSIO_DISPATCH in EOSIO smart contract

I have following EOSIO smart contract: #include <eosiolib/eosio.hpp> #include <eosiolib/print.hpp> using namespace eosio; class random : public contract { public: using contract::...

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