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Questions tagged [oracles]

Oracle is a way of implementing a Smart Contract. Instead of running the contract code directly on the blockchain, the code is executed on some special off-chain entities called oracles which then send the result of the code to the blockchain network with a signature.

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20 views

Parse two API into one JSON for oraclize

I'm working with oraclize and Solidity and I need to get a URL of the API to query, usually "json().XX". The expected format is a JSON object with 2 fields or string like so: { "portfolioValue": 100....
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7 views

ethereum-bridge: always return a callback error

I am using Oraclize for generating random number for my smart contract. I write unit test for testing oraclize things so I use ethereum-bridge written by Oraclize. Here is my problem: First: my smart ...
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1answer
35 views

How to raise version of oraclize-api installed via Truffle

I'm using local instance of Oraclize API, to make truffle compile work. I've installed it by truffle install oraclize-api but for now, I'm getting following error if (oraclize_randomDS_args[...
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2answers
77 views

Chainlink vs Oraclize [closed]

I am trying to choose between Chainlink vs Oraclize. Can anyone advise the difference between both solution? Nathan Aw
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2answers
19 views

Oraclize callback not firing on Ropsten

Testing out oraclize for a smart contract. function __callback(bytes32 _myid, string result) public { if (msg.sender != oraclize_cbAddress()) revert(); // emit LogOraclizeID(bytes32ToString(...
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1answer
12 views

Request and compare API Reponses in Oraclize call

I want to send requests to 3 Weather APIs and compare their results like if the rainfall at a specific day were the same London to avoid the single point of failure. I already learned how I can send ...
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1answer
22 views

How to test time-dependent contracts on the mainnet?

In Ganache, I use evm_mine to simulate the passage of time. Assuming block times are accurate enough, what are the best practices to test some contracts on the mainnet or a testnet which depend on ...
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13 views

How to pass arguments inside Oraclize API URL?

I am trying to call Oraclize API URL. I saw many codes related to the same. One of the example I explained below. function update(){ oraclize_query(60, "URL", "json(http://api.fixer.io/latest?...
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16 views

Can't make more than one call in oraclize (test contract deployed to local Ganache and connected via ethereum-bridge)

I am running a local instance of Ganache and I've connected my Metamask plugin in chrome to connect to the custom RPC at http://localhost:7545. I've deployed my contract onto my local test net via ...
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2answers
27 views

What is the max data and program complexity one smart-contract can support

I want to make a smart-contract for P2P trading. I am wandering if I have to create separate contracts for each bid and agreement between two entities, or I can simply create a single contract that ...
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0answers
24 views

How to handle Oraclize if it's failed?

I'm using the Oraclize to get the random number for bets. When the function bet() is called and if the oraclize is failed it should call the pingOracle() again. Below is example function bet() public ...
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2answers
20 views

Storing private data that will be decrypted by a smart contract

Another private data problem! I would like to store some data in a Smart Contract, encrypted so nobody can see it upon some specific condition (time, or whatever). For instance, after one year, this ...
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1answer
27 views

Is there a more “decentralized” way to verify an Ethereum account owns a particular Twitter handle?

Is this something fulfilled by a project like uPort? Basically, I need a way in my contracts to verify that a particular Ethereum address (0xasdf...) and a particular Twitter handle (@user) are ...
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1answer
38 views

Parsing the WolframAlpha string result from the Oracalize __callback function into a usable format?

I need to generate 10 unique random numbers between 0 to 100 in my smart contract. For this I've decided to utilise Oracalize and one of the datasource called WolframAlpha. This is how I use it: ...
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1answer
37 views

Truffle fails to migrate an Oraclize contract into Ganache

I have a contract that is using Oraclize. When deploying the contract from the Remix IDE into Ganache/Ethereum-bridge via MetaMask, the contract is fully functional. However, when trying to migrate ...
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1answer
26 views

Can i change data in a database using smart contract and oraclize?

i understand that smart contract and oraclize can be use to get data from a database but can i manipulate the data inside the database using smart contract and oraclize? If so how can i do it? Can I ...
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2answers
15 views

Oraclize: Mismatching queryId and myid

I have the following contract that uses Oraclize: contract Test is usingOraclize { bytes32 public query; mapping (bytes32=> address) senderAddress; address public resultAddress; function ...
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1answer
42 views

Using oraclize and solidity-util - having trouble splitting string separated by space

I am learning to use Oraclize to connect it to random.org to generate random numbers. Here's my test contract code: pragma solidity ^0.4.25; import "github.com/oraclize/ethereum-api/oraclizeAPI.sol"...
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1answer
17 views

Changing the contract state while waiting for the Oraclize __callback()

I have a contract that uses Oraclize to query some data. When the query is sent, a global variable address is set to the msg.sender. This is to be able to interact with the query sender in the ...
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1answer
40 views

Retrieve and store data into a local database using smart contract

For my information oraclize can be use to retrieve data from several data source but what if i need to get from a local database such as oracle,sql, etc. Is there any way of doing it? PS: I am ...
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1answer
43 views

Storing Mutliple Oraclize Queries

We have been trying to use a mapping to store multiple Oraclize queries and their results but it does not seem to be working properly. What is the ideal way to store multiple Oraclize queries by their ...
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0answers
36 views

Parsing integers from an Oraclize callback string

I have the following array that is returned by an Oraclize query as a string. [1, [2, 3, 4, 5]] I need to parse the numbers 2, 3, 4, 5 from the internal array as Integers, but having troubles with ...
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27 views

Official OraclizeAddrResolver (OAR) in Ropsten and the Mainnet

Does anyone know the official OAR addresses in Ropsten (if it exist) and in the Mainnet? As example Rinkeby testnet has this address "0x146500cfd35B22E4A392Fe0aDc06De1a1368Ed48" as official OAR.
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2answers
40 views

How to use fiat exchange rate oracle in DAPP?

my team is trying to develop a DAPP about fiat exchange rate. How to get the latest fiat exchange rate (USD/EURO etc.) accurately from external Oracles(Or are there better ways doing this)?
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1answer
63 views

Oraclize handling long response from cryptocompare

I have very custom task and I need to make sure what are limits of each technology. I haven't found nothing similair in this forum yet. I am using Oraclize to get response from this url: https://...
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1answer
55 views

Oraclize callback is not called with more data in it

I have very strange experience with Oracle. When I try to add functionality inside of callback, callback is not called, but when I delete functionality callback works without problem. I tried to ...
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1answer
36 views

Tutorial to understand technical details of Oracles in Ethereum

What is Oracles? Why is it needed? Is there any good technical blog with an example in which Oracles is explained? From whatever I read about Oracles Oracle is a trusted third party API from ...
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1answer
32 views

Updated: How to interact “directly” with smart contract via a micro-controller?

Assume we have a micro-controller and it collects a meta-data (ex. a payload as a string). How this micro-controller can interact "directly" with smart contract to write this data to the blockchain? ...
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0answers
25 views

Tutorial for ZAP inegration with Oracle

Oracle is a trusted third party API from which smart contract will fetch the data. Zap is a way to monetize the data which smart contract is getting using a token called zap token. Is there any ...
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2answers
39 views

How accurate are Etherscan's internal tx's on Rinkeby for Oraclize calls?

I'm trying to optimize my smart contract and am breaking down where the gas is being spent. Each execution for one function costs me about $5 in gas. I looked at Etherscan and in the internal tx's it ...
3
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1answer
213 views

oraclize price for random value too high (rinkeby)?

Currently, when I call oraclize_getPrice("random", 400000); I get back 8000000000000000 on rinkeby. That'd be over 2$ USD if on the mainnet and also looks oddly round. Why is this so high?
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2answers
90 views

Who is Oraclize? Is using their API dangerous?

I looked through the code of the oraclize api, and it seems that oraclize can swap out keyportions of the implementation at will. In particular, it looks like they can adjust the pricing for their API ...
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54 views

“Augur” vs. “Oraclize” : What is the main difference?

Can we say that "Augur" is a decentralized Oracle against "Oraclize" as a centralized model? I mean can we consider Augur as a decentralized Oracle and on the other hand, Oraclize as a centralized ...
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2answers
112 views

What is the Oracle Problem definition exactly and briefly?

What is the Oracle Problem definition exactly and briefly? Does it mean "trusting on a centralized Oracle" ? Or "How to reach a consensus between a group of Oracles" ? Is the matter "centralization" ...
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0answers
24 views

Oraclize random datasource, what is trusted by using it?

I'm currently looking into ways of accessing randomness in a smartcontract. I found oraclize random datasource https://github.com/oraclize/ethereum-examples/tree/master/solidity/random-datasource and ...
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0answers
19 views

How to know the price of the day of ETH in USD by Oracles?

Consider in a contract the payer intends to pay recipient ETH based on USD (ex. the salary is 1 USD but paid by ETH). So, if today contract needs to know equivalent value of 1 ETH in USD exactly at ...
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2answers
56 views

“Augur” : Is it an “Oracle” or “data-source” ? which one?

If we define following three entities (as defined HERE): (1) data-source (2) query (3) the oracle/oracle network Then, as this article says, is "Augur" a data-source ? Or it is an "Oracle" ?
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2answers
265 views

Is it possible to use “Oraclize” on a testnets such as “Ropsten” or “Kovan” or “Rinkeby” or even local blockchain such as “TestRPC”?

Is it possible to use Oraclize on a testnet such as "Ropsten" or "Kovan" or "Rinkeby" or even local blockchain such as "TestRPC" ?
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0answers
40 views

How do we deploy a smart contract with Oraclize to Rinkeby Network?

I have created a smart contract with Oraclize logic which I tested locally using Truffle. Now I want to test it on Rinkeby network along with my front end, what it the process to do so ? How do we ...
2
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1answer
45 views

question about gas limit when using oraclize

I'm using oraclize to fetch some data from the outside world. Oraclize calls the __callback method of my smart contract. For this call oraclize have to pay gas and there is a function to set the gas ...
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2answers
57 views

Detecting oraclize completion for front-end update using Web3.js

I am using oraclize-api to fetch and store twitter posts into a smart contract. Posts are placed into a mapping using the twitter id as the key (i.e. <username>/status/<id>), and the tweet ...
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28 views

Dapp design to handle delay in callback response from Oraclize

In my dapp design I am receiving few user inputs via a form and passing them to a smart contract. Inside the smart contract I am using Oraclize service to timestamp the user inputs. Its a known fact ...
2
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1answer
49 views

How to pass parameters to a function that is invoked from inside of Oraclize Callback function

In the design of my dapp I am using Oraclize to get current time. Now from its __Callback function I want to call another function to which I need to pass other parameters as well along with current ...
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1answer
157 views

How to get oraclize to work?

I tried to run the code in http://dapps.oraclize.it/browser-solidity/#version=soljson-v0.4.24+commit.e67f0147.js but I get the error VM: out of gas when I try to run the updatePrice function. I set ...
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2answers
88 views

Capturing an event fired from a contract that was called from another contract

I'm trying calculate tax on arbitrary items/values. To do this I have a single contract is used as an 'Oracle' to get the tax from an external system. This contract defines functions to be called from ...
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0answers
18 views

How to process a request with oraclize on the server?

First of all, it's the first time I use Oraclize. I have a contract makes a request to a remote server (Python) that I have, my question is, how to process that request? If I understand correctly, the ...
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3answers
75 views

Ways to Decentralize Oraclize

Based on my understanding, Oraclize is a centralized solution. What are some ways to decentralize Oraclize?
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1answer
79 views

Unable to deploy contract that uses Oraclize. Out of gas

I'm trying to deploy a smart contract that uses Oraclize on the Ropsten TestNet using truffle. It seems that deploy the Oraclize api contract (imported by my contract) it's too costly and causes the ...
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1answer
125 views

Quorum Smart Contract Avoid State Changes External Calls (Oraclize) - Deterministic

One of the Solidity best practices relating to external calls is to avoid state changes after an external call. However, does this principle still apply if one is using a private blockchain such as ...
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0answers
17 views

deploying an oracle using web3j

I want to use web3j in order to deploy an oracle (smart contract using OraclizeApi) and I don't know how to do it. normally for a simple smart contract we compile the .sol using solc and then generate ...