Ethereum icon helmets
Initially didn't like the design but the designer took feedback and created a great design. What industry do you think your business is most related to? Tell us a bit about who you are and the people you reach Publisher of iOS games. What inspires you and how do you envision the design for your business? Need a new icon for our game we are about to launch. Other notes Our company publishes games a week, so this could lead to a lot more work.
We've found some similar contests you might like. Create a Logo that infuses two major companies: A phone company, like samsung or apple, that creates beautifully designed cell phones, and accessories such as cases, We mainly build facility and construction maint applications. Some web based a Create an icon for new version of our app Emopic.
Video Encoding App for the Mac Store. A Mac app that converts video files. Users of our app will be familiar with Final Cut, and Adobe products Android app icon for a popular musician's tool.
Music Speed Changer is an Android app that slows down the speed of music without changing the pitch, or vice versa. We're an IT management company. Our logo is already designed, and I need custom icons for an application We saved a spot for your icon or button contest. Create a simple, modern iOS icon for a car utility app. We're building Copilot, an app to help teach autonomous cars how to drive by themselves. Save that file, go back to your command line, go back to the "truffle" subdirectory beneath your root "webthereum" directory, and type.
Writing automated tests for your software is always a good idea; but it's a really, really excellently awesome and important idea for Solidity code. If you don't find a bug until the code is on the blockchain, not only have you wasted a ton of time and a slew of money, your diagnosis and debugging options are very, very limited.
Did I mention that they are expensive and time-consuming, too? To its credit, Truffle lets you write test in both Solidity and Javascript.
You could make a good case for writing both kinds of tests so that you test both the VM operations, with the former, and the JS-blockchain interface but in the interests of expediency let's just whip up a Solidity test for MyPrize, called TestMyPrize. You'll notice that we don't test the metadata, and that the "claim" tests are commented out.
This is because we can't actually test either of those things; Truffle's Assert. So the claim call will fail ungracefully if we try, teaching us nothing. I did mention that the whole ecosystem is still somewhere between alpha and beta software, right?
So you wrote well, you copy-and-pasted, but it's a start your first smart contract. You tested your first smart contract. You've got a blockchain address and a private key. Now how do all these ingredients bake together into a delicious cake running in production? Pardon the mixed metaphor; I'm hungry as I type this. You could run an Ethereum client like Geth or Parity or MetaMask on your local machine, point Truffle to it, and simply type "truffle deploy".
But let's go a little more low-level, and at the same time, keep you from having to run your own local node. Infura lets you submit signed Ethereum transactions to the Rinkeby testnet via the Internet, and contract deployment is just another kind of Ethereum transaction. But you don't want to have to deal with a slew of cryptic bash commands either. You can compile and deploy entirely via Javascript, courtesy of the web3 library and the solc compiler. Let's take a look at that in a little more detail:.
First off, create a new "node" subdirectory under your root "webthereum" directory. Then go there, run. You do have NPM installed and running on your system, right?
Next, install a few new NPM packages:. Note that we're using a particular version of web3, as the latest version released two days after this tutorial was published uses different method signatures only temporarily, though, as I understand it, until 1. Once that's done, simply return to your command line and type. If you have followed all the above faithfully, and if the tutorial gods smile upon you, you will see a result like:. You have successfully submitted your smart contract to the Rinkeby blockchain.
And unless there's some unforeseen problem it will soon be mined and deployed. Let's go over what we just did. First we built a web3 Ethereum client as a Javascript object, and pointed it to the Rinkeby testnet blockchain. Then, in deployContract , we connected to that blockchain and asked it how many transactions our address had performed and in passing verified that this connection worked. We subsequently used that number as the "nonce" for our new transaction, which, to vastly oversimplify, ensures that each transaction is unique.
We then used the "solc" library to compile the Solidity code we previously wrote -- yes, that's right, we ran a Solidity compiler inside of Javascript -- and built a dictionary with all the values required for our new Ethereum transaction. This included the address of our Ethereum account, which we previously set as an environment variable, and the compiled bytecode as its payload. We also set the gasLimit and gasPrice to reasonably generous values, to ensure that we could pay for this transaction out of the money in our account, and finally sent the assembled dictionary off to the "sendRaw" method.
You can doublecheck the transaction's status by heading over to the Etherscan service for Rinkeby https: You can also use your Ethereum address to get a list of all transactions you've submitted.
Don't panic if this transaction doesn't show up immediately -- sometime it can take a minute or so. But it shouldn't take longer than that. You can get a wealth of in-depth data about your transactions from Etherscan. I encourage you to go through it in some detail. Much may not make sense at first, but, again, you'll wrap your head around it all eventually.
Now it's time to move from the command line to the browser. It should get the job done though. The principle is simple: In fact we won't even run a node on our server, though you would if you wanted to scale; instead we'll just keep talking to Rinkeby via Infura.
We will, however, also create a very simple HTML page for browser consumption, which for now just lets users check on the state of our ten prizes. This time, however, you cannot run the code out of the box. You have to fill in the "contractAddress" and "abi" values at the top first. The contract address is straightforward enough: Note that it's a string, i. You could also set and use it as an environment variable, as before, but note that the Ethereum contract address is different from your Ethereum account address.
A very very simple HTML form should appear. Hit "submit" and you should get some raw JSON back, such as Not super-interesting, yet -- but what's important is that this is real live data coming from your Solidity smart contract, running on the Rinkeby blockchain, to the browser, via your Node service! Give yourself a pat on the back for making this happen; you've earned it.
In order to call the contract, your Node code needs to know its interface, aka its ABI, which is hardcoded above. In theory, you should be able to recompile your Solidity contract from source and use its.
In practice that seems to not actually work. So, if you change the MyPrize contract, do the following: Uncomment the "showABI " line. Then run "node deploy. The new contract will be deployed, to a new address, and the ABI will be logged to the console. Now, copy-and-paste that ABI back to index1. OK, let's put it all together; let's run a Node web service that you can use to place prizes, to claim prizes, and, what's more, let's add in a Postgres database that you can use to track prize data and transaction information.
Because a blockchain is hugely inefficient with respect to both ease-of-development and performance. One answer which springs to mind: Explaining Postgres is way out of the scope of this tutorial, I'm afraid, so this section assumes a basic degree of comfort with databases in general and Postgres specifically. Once you've done that, here is a new and substantially larger file, index. You can also view the data stored in the local database, and check the details of what the database thinks is the most recent blockchain transaction relating to that prize.
Note however that this is highly asynchronous. When you "place" or "claim" a prize, you're really just submitting a transaction to the blockchain; it takes a minute or so, an eternity in web time, for that transaction to be accepted or rejected. It might be rejected because e. In a real web app this delay must be handled by the server code, and communicated to the user, in an elegant manner.
Otherwise there isn't a lot of conceptually new code here. As with the previous section, you use the Node service as an intermediary between the blockchain and the browser. As with deploying the contract in the first place, to write data to the blockchain you build Ethereum transactions and sign them. The big difference here is that we aren't restricted to a single address stored in an environment variable; we let anyone with a blockchain address and private key perform these transactions. On the one hand this approach arguably combines the decentralized power of blockchain apps with the accessibility and scalability of web applications.
On the other, though Private keys are called that for a reason. Ethereum addresses can hold very, very significant amounts of money, and their private keys should be guarded accordingly. This means that as a general rule you should not ever be pasting them into a browser. You face potential client-side plugin attacks, Man-in-the-Middle attacks, cross-site scripting attacks, server-side hack attacks, etc etc etc.
It's fine for this tutorial which uses fake money, of course.