Ethereum transaction history

In Solidity, events are dispatched signals the smart contracts can fire. Event can also be indexed, so that the event history is searchable later. The most common event on the Ethereum blockchain at the time of writing this article is the Transfer event that is emitted by ERC20 tokens when someone transfer tokens. The event signature are declared inside of the contract code and can be emitted with the emit keyword.

For example the transfer event logs who sent the transfer from , to who to and how much tokens were transferred value. If we get back to our Counter smart contract and decide to log everytime the value is changed. In the case of our counter example it would look like this:. Line 5 : we declare our event and what it contains, the old value and the new value. Line 13 : When we increment our count variable, we emit the event.

Logs are really useful for debugging your smart contracts but they are also important if you build applications used by different people and make it easier to make analytics to track and understand how your smart contract is used. The logs generated by transactions are displayed in popular block explorers and you can also for example use them to create off chain scripts for listening to specific events and taking action when they occurs.

Помогите перевести эту страничку. Anyone can read or create transactions on a public blockchain and validate the transactions being executed. Agreement on transactions and the state of the network is decided by a consensus of peers. Mainnet is the primary public Ethereum production blockchain, where actual-value transactions occur on the distributed ledger. In addition to Mainnet, there are public testnets. These are networks used by protocol developers or smart contract developers to test both protocol upgrades as well as potential smart contracts in a production-like environment before deployment to Mainnet.

Think of this as an analog to production versus staging servers. Most testnets use a proof-of-authority consensus mechanism. This means a small number of nodes are chosen to validate transactions and create new blocks — staking their identity in the process. A proof-of-authority testnet that works across clients.

A proof-of-authority testnet for those running OpenEthereum clients. A proof-of-authority testnet for those running Geth client. A proof-of-work testnet. Most faucets are webapps where you can input an address which you request ETH to be sent to. An Ethereum network is a private network if its nodes are not connected to a public network i.

Mainnet or a testnet. In this context, private only means reserved or isolated, rather than protected or secure. Similar to how you create a local server on your computer for web development, you can create a local blockchain instance to test your dapp. This allows for much faster iteration than a public testnet.

There are projects and tools dedicated to assist with this. Learn more about development networks. The consensus process is controlled by a pre-defined set of nodes that are trusted. For example, a private network of known academic institutions that each govern a single node, and blocks are validated by a threshold of signatories within the network.

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