How to Fetch Data From the Ethereum Blockchain Using Swift | by Lee Kah Seng

How one can use web3.swift in iOS

How to Fetch Data From the Ethereum Blockchain Using Swift

Ever for the reason that introduction of the Ethereum blockchain within the yr 2015, it has revolutionized the whole software program growth trade. It’s the first blockchain that has good contract functionality, permitting builders to create and deploy decentralized functions (dApps) that work together with the Ethereum blockchain.

These days most dApps are web-based functions. Nevertheless, I do imagine that cellular native dApps will develop into increasingly fashionable when blockchain know-how will get higher adoption over time.

On this article, I’ll present you how one can create a easy dApp that fetches the most recent fuel value from the Ethereum Mainnet. All through the method, you’ll learn to achieve entry to a public node, what library it’s best to use in your Xcode venture, and how one can join & fetch knowledge from the Mainnet.

With out additional ado, let’s leap proper in!

In case you are studying this text, I assume you have already got some fundamental concept of what a blockchain is. In case you don’t, you possibly can consider it as a huge server consisting of 1000’s of nodes hosted all all over the world.

Professional tip:

Take a look at this web page for all of the Ethereum nodes presently accessible across the globe.

The best way to fetch knowledge from the Ethereum blockchain is similar to the way you fetch knowledge from a centralized server. As an alternative of connecting to a centralized server, we’ll hook up with an Ethereum node that exposes a list of JSON-RPC methods (API endpoints). By utilizing the offered API endpoints, we are able to then carry out actions akin to getting the present fuel value or getting the stability of an handle.

Does this imply that we have to arrange our personal Ethereum node with a purpose to get began? Properly, not essential.

There are third-party providers on the market akin to Infura and Alchemy that present APIs to a public node. All we have to do is subscribe to their free tier service, then we’re good to go. For this text, Infura can be our foremost focus, however you possibly can undoubtedly use Alchemy if that’s your most popular selection.

As soon as we’ve the node in place, fetching knowledge from the Ethereum blockchain is only a matter of calling the API endpoints. For our pattern app, we can be utilizing a web3.swift library developed by Argent Labs to ease us in interacting with the Ethereum blockchain.

With the essential idea out of the way in which, let’s head over to Infura and get issues began.

As you might need guessed, the very first thing it is advisable do is to create an Infura account. You are able to do it here.

When you will get your account up and operating, head over to the dashboard and create a brand new venture:

Using Infura for iOS dApp development
Infura dashboard

Within the new venture dialog, select “Ethereum” as product and fill within the venture identify you want:

Create a new project in Infura for iOS dApp development
Create new venture in Infura

As soon as the venture is created, you’ll be redirected to the venture settings web page. That is the place you will get the JSON-RPC endpoint of your venture:

Obtaining JSON-RPC endpoint in Infura for iOS dApp development
Getting venture endpoint in Infura

If you do not need to check your dApp on the Ethereum Mainnet, you need to use the dropdown menu to change to testnets akin to Ropsten and Rinkeby to get their respective endpoints.

Switching endpoint in Infura
Switching endpoint in Infura

With that, we’ve efficiently arrange Infura and might now begin utilizing the given endpoint to work together with the Ethereum blockchain.

The JSON-RPC methodology that we are able to use to get the present Ethereum fuel value is eth_gasPrice. In case you check out the API specification of the tactic, you’ll discover that the response physique is as observe:


"jsonrpc": "2.0",
"id": 1,
"end result": "0x12a05f200"

the place the fuel value (end result) is represented by a hex code of an integer.

You may undoubtedly carry out a submit request to the eth_gasPrice methodology and manually parse the given hex code again to an integer, however that’s method too troublesome! Let me introduce you to a significantly better solution to cope with such a scenario — by utilizing the web3.swift library.

The web3.swift Library

As talked about earlier, the web3.swift library is developed by Argent Lab, the crew behind the well-known cellular DeFi pockets “Argent”. Their major purpose of open-sourcing the library is to facilitate easy accessibility to the Ethereum blockchain through a Swift native library, primarily for the creation of decentralized iOS apps. Due to this fact, in the event you just like the library and want to assist what the crew is doing, be at liberty to offer them your suggestions and contribute to the library.

Now again to the library itself, it’s mainly a wrapper class for a few of the mostly used strategies of the Ethereum blockchain. It takes care of all these heavy lifting duties akin to API calling and JSON parsing for us. The very best half is that it even helps the brand new Swift Concurrency (async/await) syntax.

Professional Tip:

After you put in the library, try EthereumClientProtocol outlined in EthereumClient.swift to see all of the JSON-RPC strategies supported by the library.

To get the fuel value from the Ethereum blockchain, all we have to do is to create an occasion of the EthereumClient utilizing the endpoint we obtained from Infura, and name the respective shopper methodology accordingly.

One factor to pay attention to is that the eth_gasPrice() methodology returning kind is BigUint, which is an integer kind that’s wider than UIntMax. Due to this fact, we are able to use the quotientAndRemainder(dividingBy:) operate offered by BigUint to transform the given fuel value from wei to Gwei.

With that, you might have efficiently created your first decentralized iOS app that runs on the Ethereum blockchain. Technique to go!

On this article, I solely cowl the naked minimal of what it is advisable know so as so that you can get began with dApp growth utilizing Swift. There are nonetheless a number of matters surrounding cellular dApp growth akin to connecting to a pockets, dealing with transactions, and many others. that I’ve but to cowl.

At this second, I’m nonetheless on the stage of exploring and studying. I’ll proceed to share what I’ve discovered right here on Medium, so please keep tuned for extra articles like this within the close to future.

Thanks for studying.

Wish to Join?Within the meantime, you possibly can observe me on Twitter and take a look at my web site for articles associated to Swift and iOS development.

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