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DevChain
No gas needed. Accounts are only for identification purposes.
The smart contract is very simple. It provides the text and image url to be voted on, and keeps a record of votes. The
vote() method is called by voters to vote thumb up or down. pragma solidity >= 0.4.0;
contract Vote {
string public greeting;
string public photoUrl;
mapping (address => int) votes;
uint ups;
uint downs;
constructor(string _greeting, string _photoUrl) public {
greeting = _greeting;
photoUrl = _photoUrl;
}
function vote (int _choice) public {
require (votes[msg.sender] == 0);
require (_choice == 1 || _choice == -1);
votes[msg.sender] = _choice;
if (_choice == 1) ups++;
if (_choice == -1) downs++;
}
function getVotes () view public returns (uint, uint) {
return (ups, downs);
}
function getVote (address _addr) view public returns (int) {
return votes[_addr];
}
}
The contract is now deployed on the DevChain, and you can call its functions directly from inside BUIDL.
<div class="container">
<br/>
<div class="jumbotron">
<p class="lead" id="greeting"></p>
<div id="imageDiv" style="display:none">
<img id="image" src="" class="img-fluid img-thumbnail"/>
</div>
<hr/>
<p id="votes" style="display:none">
<span id="ups"></span> voted 👍 |
<span id="downs"></span> voted 👎
</p>
<form id="form" class="form-inline" style="display:none">
<button id="voteUp" type="button" onclick="return vote(1);" class="btn btn-secondary mb-2">👍</button>
<button id="voteDown" type="button" onclick="return vote(-1);" class="btn btn-secondary mb-2">👎</button>
</form>
<div id="formSubmitted" style="display:none">Please wait 2 seconds ...</div>
<div id="myVoteUp" style="display:none">You have already voted 👍</div>
<div id="myVoteDown" style="display:none">You have already voted 👎</div>
</div>
</div>
var instance = null;
window.addEventListener('web3Ready', function() {
var contract = web3.ss.contract(abi);
instance = contract.at(cAddr);
reload();
});
function reload() {
instance.greeting(function (e, r) {
$("#greeting").html(r);
});
instance.photoUrl(function (e, r) {
if (!e && r) {
$("#imageDiv").css("display", "block");
$("#image").attr("src", r);
}
});
instance.getVotes(function (e, r) {
if (!e && (r[0] > 0 || r[1] > 0)) {
$("#votes").css("display", "block");
$("#ups").text(r[0]);
$("#downs").text(r[1]);
}
});
$("#form").css("display", "none");
$("#formSubmitted").css("display", "none");
web3.ss.getAccounts(function (e, address) {
if (!e) {
instance.getVote(address, function (ee, r) {
if (r == 1) {
$("#myVoteUp").css("display", "block");
} else if (r == -1) {
$("#myVoteDown").css("display", "block");
} else {
$("#form").css("display", "block");
}
});
}
});
}
function vote (choice) {
web3.ss.getAccounts(function (e, address) {
if (!e) {
$("#form").css("display", "none");
$("#formSubmitted").css("display", "block");
instance.vote(choice, function (ee, result) {
if (ee) {
window.alert("Failed for " + address);
}
});
setTimeout(function () {
reload ();
}, 2 * 1000);
}
});
return false;
}
Just click on the Publish button and give the dapp a name. Once published, you can share the published URL to the public to vote on your issue! Notice that the DevChain requires no gas to operate. So the user can vote from any of the auto-created or imported DevChain accounts.
Last modified 4yr ago