以前はMeteorとgeth, Mochaを利用して、2アカウント間の送金のテスト、コントラクトへの送金のテストを行いました。 今回は実際にMeteorからコントラクトへ送金し、Solidityで記述したスマートコントラクトの関数を動かしてみようと思います。 Meteorの使い方は Meteorのドキュメント に詳しく書かれています。 やりたいこと ボタンのclickイベントを受け取り、コントラクトへ送金する トランザクションをMeteorのCollectionで管理する マイニングが完了したことを検知する スマートコントラクトの状態を確認する 気をつけること: MeteorとEthereumを分離する 実装に入る前に、Dapp using Meteor に書かれていたアドバイスを確認します。 put ethereum related stuff into client/lib/ethereum/somefile.js use myCollection.observe({added: func, changed: func, removed: func}) to communicate to ethereum, keep ethereum logic out of your app as much as possible.

This way you just write and read from your reactive collections and the observe functions will handle the rest (e.g.bitcoin mining saudi arabiasendTransactions) Filters etc will add logs etc to your collections.bitcoin mining saudi arabiaSo you keep all the callback mess out of your app logic.bitcoin telugu videosEthereumに接続する部分を、なるべくMeteorから分離することがポイントのようです。 これを踏まえて、前回のテストコードから改善する方針を立てます。 前回のコードからの改善点 スマートコントラクトの一連の流れを試すために複数のトランザクションを発行するので、それらをCollectionに入れて管理する トランザクション発行後、マイニングが完了したことの検知をsetIntervalではなくeth.filterで行うようにする Collectionの状態監視、マイニング完了の監視をclient/lib/ethereum/observeTransactions.jsとして分離する これらに気をつけながら実装を行っていきます。 トランザクションをMeteorのCollectionで管理する まずは、Blockchainへ発行したトランザクションをMongoDBで管理できるようにします。 = .(,bitcoin ard

{: ボタンのclickイベントを受け取り、コントラクトへ送金する Meteorのtemplateにボタンを設置し、JS側でボタンのclickイベントを受け取ります。 コールバックでトランザクションを発行します。 < =>< =>> > ..: { = {: ,: ,: ..[0]bitcoin dac{ : {: } } contractInstance.PurchaseのコールバックでCollectionを作成します。 Collectionの経過の監視のコードを、マニュアルの通りclient/lib/ethereum/に置きます。 Transaction.observe({added: func, changed: func, removed: func})のように記述することで、レコードが作成・更新・削除されたことを受け取ることができます。 [.] = .: () {.((:bitcoin akcjeマイニングが完了したことを検知する web3.eth.filter("latest").watchを設定すると、新しいブロックが来るごとにコールバックを実行することができます。 このコールバックの中で、該当のトランザクションのマイニングが完了しているかをチェックし、完了していた場合はウォッチを停止します。 = ..(((e,goodbye bitcoin hello bitcoin

(e, ) { (e !() {.} スマートコントラクトの状態を確認する スマートコントラクトを作成する際のコツのひとつに「状態を設定しておく」というのがあります。 (Youtubeにライブコーディングの動画 があるのでぜひ見てみてください) このスマートコントラクトの例では、何度かトランザクションを発行していくことによって、スマートコントラクトの状態が変化していきます。 例えば商品が陳列された状態であれば、次のアクションは購入ができるようにする、というように、状態を検知して、その状態ごとにログをとったり、アプリの次のアクションを変えていきます。 状態検知の方法は2種類あります。 - 状態(State)を取得 - イベントを検知 Solidity側でのイベントおよび状態の記述はこのようになっています。 状態を取得する Stateがpublicになっているので、call()メソッドで取得することができます。 enum型で設定していますが、戻り値はBigNumber型になっているようです。 イベントを検知する スマートコントラクト内で発行したイベントをウォッチし、検知していきます。 イベントのウォッチは、Javascript APIのContract Events を参考に設定しました。 今回はallEventsを使ってすべてのイベントをウォッチしましたが、特定のイベントのみを受けることもできるようです。 = .(bitcoin lottery legal

.} まとめ Meteor、MongoDBとgethを利用して、スマートコントラクトのインスタンス作成、関数の実行、状態の監視を行いました。 今回作成したコードはGitHubにありますので、もしよければご覧ください。 gethとの接続監視など、より高機能なアプリを作りたい方は、Meteor Dapp Wallet が非常に参考なるので、そちらもご覧ください。 azusa-kikuchi 人気の投稿 geth, Meteor上で簡単なアプリ(Dapp)を作成する geth, Meteor上で2アカウント間の送金テストを行う geth, Meteor上でコントラクトへの送金テストを行う Whisperを調べてみた Yours のテストユーザーになった話bitcoin kaufen kontoIt was exactly two weeks ago, when I was with an old friend on the phone and he introduced ethereum to me.The conversation went like this: "Hey, do you have a day or two to hack something fun?"

- "Yeah, why not".Two weeks later, I had finished what he asked me for.I cannot really say here what I was doing, because its confidential, but I can talk about the things I learned along the way and can introduce a few things.Things which are important to newcomers at the DApps-Land.First, I will cover some misconceptions to people who are completely new.Then I will show some basic stuff you can do with Solidity.Then we will deploy a simple contract and try to call a function from an angular app.This should be enough for this tutorial.In the next tutorial we are going to see how events work and how we can call a contract from another contract and send an ether-value (with address.call.value()() - my new favorite).It was very difficult for me to understand (and see the difference between) the terms The two documentations you should at least have open in a tab: Web3 is, as far as I understand, meant as a library of JavaScript functions.It's a library actually.When you use bower for your projects you could do like bower install --save web3 and it would install the web3-js library.

Then you can do things like var web3 = new Web3(); web3.sha3('test123()'); You can also do other things, which I will cover in the next chapter below.The Ethereum Blockchain has to be accessed by clients.And all of those are clients do (more or less) exactly the same.GETH (Go-Ethereum) is written in go and does the same as CPP-Ethereum (written in C++).The only major difference is that with CPP-Ethereum there is AlethZero and Mix included.Which you might need, or not.See here for an overview.I had major troubles getting CPP-Ethereum (and Mix and AlethZero) to run.I was running Windows 10 at that time, so maybe it was the reason.Although I saw the same problems on a Mac.The programs just kept crashing.On the other hand, once AlethZero is running it is an ease to setup a private chain to try around with Contracts.Mix is supposed to be an IDE, but its really in its infanties from my point of view.In order to connect to the blockchain you need to open GETH or CPP-Ethereum, which is  nothing else than a node downloading all blocks.

The blockchain is a state-machine and every time a transaction takes place the state is updated.So, you can always see at which block what transaction took place.Back to the origin.Solidity, Serpent and others are high-level languages you can write DApps in (DApps = Distributed apps).In order to let DApps "run" they are getting compiled into EVM.You don't have to write in Solidity, you can also write it in other languages, but your best choice at the moment is probably Solidity.There are numerous "IDE"s (well, more like editors with a few benefits) you can write your DApps in.If you are used to Visual Studio, IntelliJ or something similar, you probably have to wait a bit.Once the source is compiled it cannot be "de-compiled" into the high-level source code back.What you see is something similar like assembler language - and every instruction costs "gas".Those are releases of the Ethereum Blockchain.The current one is Homestead, the last one Frontier.When you read current documentation, be careful if that was written for Homestead.

Sometimes, or mostly things also work from the documentation written for Frontier, but be careful.In this chapter we cover the following details: You probably have seen the very simple example in the Solidity Documentation.Lets stick with this example a bit.Open up your Browser-Solidity and copy and paste the code in.Here is the code again for reference: lets extend it and add a kill functionality and a constructor.I will not cover here how the things work, please read the Solidity documentation - it is explained there extensively.What I will cover are the missing parts: how to make use of this from a static website hosted on github pages.How can we access this contract now?And how can we deploy it?There are probably several ways to do that.I have tried to test-deploy my contracts with AlethZero in a test-blockchain but I utterly failed - it will just silently make contracts disappear.I have also tried to "simulate" a read/write with the browser-solidity tool.You can actually do that, but at some point it just stopped working - especially for bigger contracts.

The only really easy way I found was deploying my contract using MIST in the live-blockchain.After debugging it with MIX or browser-solidity I mostly deployed it directly and saw how it will work.You find all the information you need for accounts and ways to access accounts in the official documentation.It is also mentioned there that MIST is beta-ware.Yes, I can confirm this.But nevertheless, it looks beautiful, mostly works and makes deploying contracts a breeze - on the live blockchain.You can just download the wallet and open it.It will takes ages.It will download the whole blockchain.At the time of writing, on my 100MBit/s connection, it would take probably close to 10h - maybe it has changed already.The only way I found to get around is installing GETH and running it with the following commands: and if you already have downloaded like 10%, just remove the whole db first and then run geth: after that it should download the chain within 1-2h.When you want to publish a contract you can do that by clicking on "Contracts" (on the right - written here "Verträge" - the german version) and then copy&paste the Solidity Sourcecode.

Copy and paste the SimpleStorage Contract (including the kill() function) there and publish it.What you get is an address.The contract is now reachable via an address.Now the normal way to work with web3 seems to be via a local HTTP Provider.You could do something like this: You have probably seen it multiple times.It is a lot of fun to work with Javascript that way.In order to make use of the localhost:8545 I ran into multiple problems.to circumvent that problem you have to start GETH with the correct parameters: The ABI is the Interface.When the contract is deployed the web3 library must know (in advance) what parameters and functions are available - and what is returned.To know that, there is a json-interface that looks like this: and the whole contract could be deployed with a command like this: You cannot really copy and paste it, I abbrevated the "data" field, but you get the idea probably.If the contract is already deployed then you can simple use it in web3.It looks almost the same as the ABI definition itself - mind the difference.

If you have the local GETH RPC running, you can just simply add the existing contract you published in the previous chapter to your Javascript Web3.Use Then you can do things like Super simple :) But here is the caveat: That only works when you have a local (or remote) HttpProvider for web3 - a geth node installed.And to my best knowledge, there is no public HttpProvider.You have to download geth (or cpp-ethereum) and run it yourself.Which is really annoying if you want to deploy to github pages.What comes in handy is the API from Etherscan.The guys from etherscan have built an API around that.But it is a bit tricky to access it - for newcomers.While getting account-balance information is relatively easy, it becomes harder to access functions.Basically you can only access functions that are declared as "constant".Because such functions do not require any gas - they just return a value.Lets say the address from your SimpleStorage contract is 0x111222DEADBEEF then you could query the balance for the account like this: Without any APIKey Etherscan will allow somewhat 5 requests per second.

That is what they write on their website - no idea if that is by IP or address or action.Before we can access functions in Etherscan, we have to know how to call functions in web3 natively.In order to call functions in web3 natively, you have to take the first 4 bytes from the Keccak Hash and hex encode it.Sidenote: The example in the link doesn't work properly, because web3 automatically adds the 0x for hex encoding.Our ABI Interface from our sample contract sais the function "get" takes no inputs but returns one uint256 as output.that means, we can access it (in angular) JS like this: And then we can call the Etherscan API with the $http object in AngularJS easily.What do we see here?we call an etherscan url for an "eth_call" action and call the "get" function from our SampleContract when "self.getAddress()" is returning the correct address.I will expand this sample in the second blog post, but for now it should really help you to get along."get" returns an uint256 and this can be transformed into a normal integer with web3.toDecimal(the_payload) as seen in the sample.

Retrieving values doesn't cost gas or anything, that is why this can be done via the web API without the need to send GAS.We have another function in our SampleContract that is called "set".From the ABI Definition it sais: it sais that it takes one uint256 as input parameter.While the example shown here will not work with the etherscan api, because you would have to add some gas, it shows you something else: How to properly encode the payload data manually.Again from this page we can read, that we have to pad our input parameter with 32 bytes.While my padding version is probably not the nicest one, it will do the job: The whole hex-string has to be padded to reach 32 bytes (64 times "0").web3.toHex(5) delivers 0x5 - we want to part after "0x" - so we take the substring from the second character on, which is "5".and then we put the things together and return the value.Then we need to construct the payload.We still need the function call Keccak Hashed.But this time we need to hash "set(uint256)", because the "set" function takes one uint256.