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Questions tagged [solidity]

Solidity is a high-level language whose syntax is similar to that of JavaScript and it is designed to compile to code for the Ethereum Virtual Machine. A contract in the sense of Solidity is a collection of code (its functions) and data (its state) that resides at a specific address on the Ethereum blockchain.

Solidity is a high-level language whose syntax is similar to that of JavaScript and it is designed to compile to code for the Ethereum Virtual Machine.

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What is address(0) in Solidity

Can anyone explain to me what address(0) is in Solidity? I found the following in the docs but it doesn't really make sense to me: If the target account is the zero-account (the account with the address 0), the transaction creates a new contract.…
pizzarob
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Are there null like thing in solidity

struct buyer{ uint amount; Status status; } mapping(address=>buyer) public buyers; mapping(uint=>address) buyerIndex; uint public buyerNum; //Order a product. function(){ uint doubleValue=value*2; …
Hao WU
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How to find out if an Ethereum address is a contract?

An address in Solidity can be an account or a contract (or other things, such as a transaction). When I have a variable x, holding an address, how can I test if it is a contract or not? (Yes, I've read the chapter on types in the doc)
bortzmeyer
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String concatenation in solidity?

how do i concatenate strings in solidity? var str = 'asdf' var b = str + 'sdf' seems not to work.. I looked up the documentation (https://github.com/ethereum/wiki/wiki/Solidity-Tutorial#elementary-types-value-types) and there is not much mentioned…
tObi
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How to return mapping list in Solidity? (Ethereum contract)

I want to make simple smart contract that has a list, can set item, and can get the list. Code in solidity: contract lister { mapping(int => string) list; int id = 0; function getList() returns ( /*HERE*/ ) { return list; …
6londe
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UnhandledPromiseRejectionWarning: Error: The contract code couldn't be stored, please check your gas limit

I am trying to deploy my simple solidity smart contract onto the Rinkeby Network but I keep getting the error: UnhandledPromiseRejectionWarning: Error: The contract code couldn't be stored, please check your gas limit. My solidity code is…
Jason
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npm solc: AssertionError [ERR_ASSERTION]: Invalid callback specified

I am trying to compile solidity smart contract using npm solc. I tried to follow different examples. Link to example: https://medium.com/coinmonks/how-to-compile-a-solidity-smart-contract-using-node-js-51ea7c6bf440 I wrote my code like…
Mouazzam
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Handling user profiles in Ethereum DApps

I'm in the process of creating an Ethereum DApp. The DApp consists of users who have associated data like email, name, and a profile picture. I would like to store the contents of the user within IPFS as a JSON object and reference this on chain…
Dondrey Taylor
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Copying of type struct memory[] memory to storage not yet supported

How do I add a new empty Parent instance to the list of parents in the code sample below? I keep getting UnimplementedFeatureError: Copying of type struct Test.Child memory[] memory to storage not yet supported. Minimal example: contract Test { …
Jonas H.
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String array in solidity

I came across quite a common problem that it seems I can't solve elegantly and efficiently in solidity. I've to pass an arbitrary long array of arbitrary long strings to a solidity contract. In my mind it should be something like function…
Fabio
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Is there a pop functionality for solidity arrays?

I have used solidity to push data into an array. Is there a similar function for pop ? string[] myArray; myArray.push("hello") What is the best solution for this ? How do I delete an element in a dynamic array in solidity ?
Suraj Kohli
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who is the owner of the contracts deployed using truffle?

I am using testrpc and truffle to test my contract. When I type truffle migrate , this will deploy my contract to the testrpc network. My question is , which account (from testrpc accounts) has been used to deploy the contract. In other word, whose…
sheemar
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Converting Object Promise to String in Javascript

I'm working with React, Next.Js, semantic-ui-react and Solidity. It is my goal to print out the users address (from MetaMask) and a ProjectTitle (set by User) as meta infomation for a semantic-ui-react card. To print out the address in the 'header'…
Saensation
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web3 websocket connection prevents node process from exiting

I have a node js process that creates a web3 websocket connection, like so: web3 = new Web3('ws://localhost:7545') When the process completes (I send it a SIGTERM), it does not exit, but rather hangs forever with no console output. I registered a…
Andy Pang
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Module is extraneous npm

I obviously check there is connect-privkey-to-provider module in dependencies. However, it keep saying Module 'connect-privkey-to-provider' is extraneous npm and cannot find module 'connect-privkey-to-provider' What's wrong with my code? PS…
1Sun
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