The ERC-721 standard helps make buying and selling unique digital items (NFTs) safe and reliable. It is crucial to secure transactions between two parties. That is where escrow services come in. They act like a safety net, holding an NFT until everyone agrees and all rules have been met. Let's explore how we can develop an escrow using the ERC-721 standard using OpenZeppelin implementation.
Nested mappings in Solidity offer developers powerful tools to efficiently organize and manipulate complex data structures. This blog post explores how to use nested mappings and their practical applications and provides transformative examples in smart contract development.
Developers need to understand the difference between tx.origin and msg.sender in Solidity. These two global variables often need clarification with each other despite their fundamental differences. While they may appear similar at first glance, tx.origin and msg.sender represent distinct addresses in the context of a transaction. In this blog post, we will delve deeper into the meanings of each of these variables.
In Ethereum Improvement Proposal 4337 (ERC-4337), account abstraction simplifies user interaction and the blockchain. It eliminates the need for users to deal with the complexities of wallets, making blockchain applications (dApps) more accessible to users. For instance, users can use social login to interact with dApps, and there is no need for private keys or seed phrases anymore. In this series of posts, I will provide a high-level overview of the topic in this post and dive into the code in the following ones.
The Solidity programming language for Ethereum smart contracts, offers a robust feature known as structs that is indispensable in organizing and structuring information. These user-defined data types allow us to bundle variables under a single name, effectively creating blocks of organized data with set boundaries. Not only do structs enhance code readability and maintainability, but they also offer flexibility in instantiation. There are three ways to instantiate a struct in Solidity, each with advantages and use cases. In this blog post, we'll explore the nitty-gritty of Solidity structs, exploring their significance.
Solidity's custom errors offer significant advantages in blockchain development, enhancing smart contract robustness and clarity. These errors provide detailed and precise error messages, improving the ease of issue diagnosis. Additionally, they strengthen code readability by allowing for clear naming of error conditions and improve gas efficiency by enabling compact encoding of error information. Embracing these custom errors can revolutionize your Solidity development experience. Let's see how we can use custom errors in our Ethereum smart contracts.
A Set structure, as used in many programming languages, is a collection of distinct elements where each item is unique, and no duplicates are allowed. This data structure is especially valuable when you need to efficiently check the existence of an item, maintain an organized collection of items without repetition, or quickly retrieve unique elements. Solidity programming language for Ethereum smart contract development does not natively support the Set data structure. Developers need to create their own structures or utilize external libraries to replicate Set functionalities, such as ensuring the uniqueness of elements within a collection.
With the release of iOS 17, Apple introduces an exciting enhancement to SwiftUI that revolutionizes how we add markers on maps. With the new SwiftUI in iOS 17, you can easily customize markers to match your app's aesthetic and branding, allowing seamless integration with your overall user interface. This article describes how to add and style map markers in iOS 17 with SwiftUI. Keep in mind that this is still in beta and can change.
NFT minting on Ethereum can be expensive due to the high gas fees associated with executing intelligent contract transactions on the blockchain. Previously we learned how to use the ERC-721 standard, but there is an improved standard, ERC-721A, by Azuki. It gives enormous gas savings when minting multiple NFTs in one transaction. Minting five NFTs can save 7.2 times gas compared to the original ERC-721 standard. Let's check it out in this article.
In a previous blog post, we discussed the importance of verifying Solidity smart contracts before deploying them onto the blockchain. However, there is a way to automate that process and make it more efficient. With the help of Hardhat, a popular development environment for Ethereum, developers can now verify their smart contract code programmatically as part of the deployment process. This means the verification process can be integrated into the development pipeline, ensuring the code is verified automatically each time the contract is deployed. This blog post will explore how to use Hardhat to verify smart contract code and streamline the verification process programmatically.
Smart contract verification is crucial for ensuring transparency, trust, and safety for users in the blockchain ecosystem. Smart contracts are immutable. Once deployed on the blockchain, they cannot be modified or deleted, making verification an essential process to ensure their correctness and safety. Verifying smart contracts with Hardhat tooling is a straightforward process that can be done quickly and easily. It provides a simple and effective way to verify smart contracts on the Ethereum network.
With the rise of NFTs on the Ethereum blockchain, creators can now monetize their digital art, music, videos, and other media in ways previously considered impossible. However, with the ownership and transfer of NFTs comes the question of royalties when creators receive payments for subsequent sales of their work. In this article, we will explore the concept of royalties in NFTs on Ethereum and how they are changing the landscape of digital ownership and creation.
In the previous post, we discussed meta transactions and the EIP-712 standard. This time we will check out how to sign the transaction with Ethers.js library and execute it in a smart contract. That means that the gas fee will be paid by someone else.
Meta transactions in Ethereum blockchain is an approach that removes the complexity for our users to deal with gas fees. The gas fee is a transaction fee paid to validators for proof of stake (POS) or miners for proof of work (POW) blockchains. With this approach, users sign a transaction, which is sent to a smart contract. It keeps all the security aspects upon which the Ethereum blockchain was created. This article will examine the EIP-712 standard and how to sign transactions with Metamask.
The non-fungible tokens, or in short NFTs, have one the most influential roles in the crypto and Web3 scene. These are digital assets that can represent digital art, virtual collectibles, assets in games, and more. Ethereum Foundation introduced the ERC-721 standard in 2017, which helped all the crypto wallets, brokers, and protocols to use this feature in a translatable way between any crypto solution. In this post, we will look more deeply into the ERC-721 standard and explore how it is used in the Solidity programming language for the Ethereum blockchain.
Bytes and Strings have a special place in the Solidity programming language. Both of these types work quite similarly yet differently. Even bytes have two kinds of ways - fixed or dynamic size. Bytes and strings can be converted and vice versa according to our needs to work with them. Let's look more profound in this blog post.
This time let's talk about fungible tokens, one of the main building blocks in DeFi. These tokens can represent coins, gold, grain, and other assets that can be exchanged for them. We will look into one of the first Ethereum Improvement Proposal with number 20. This token standard is widely known as ERC20 and describes an interface for tokens within smart contracts. Functions like token transferring, approving spending, creating, and others are defined by this ERC20 standard.
One of the weirdest Solidity programming language's quirks is the absence of null. Coming from Swift, where nullability is one of the core building blocks, it felt foreign. At first, I didn't understand how to code without such a useful feature. This post elaborates on how to find a way around that in Solidity when building smart contracts.
This time we will talk about the critical lower-level function delegatecall. It is widely used in a proxy pattern, for instance, when using OpenZepplin upgrades pattern. Essentially this function executes code in another contract but uses data from the caller concept. Let's dig deeper and explore more.
This time, we will talk about storage locations in Solidity programming language, specifically about the storage and memory locations. Not knowing what they represent and how they work can cause issues in our smart contracts.
Events in Solidity programming language help inform when something has happened in the smart contract. Parties like a web frontend, data gathering tools, and more can listen to specific events and react accordingly. In this post, we will dig deeper into Events and how to use them when developing smart contracts on Ethereum-like blockchains.
Mappings in Solidity programming language play a significant role. These are hash tables that can have a key and value. When we use them, there are some caveats, especially from other programming languages. Let's explore them in this article.
Arrays in Solidity programming language can hold primitive data types like integers, boolean, and string. An array can be initialized with a fixed or dynamic size. If we compare them to other more advanced programming languages, there are pretty limited functions available to work with arrays. Despite that, we can add, remove, get the size of the array, and more.
Solidity language allows specifying accessibility for contract functions and state variables. That will enable us to set constraints on constructing the smart contract and whether other contracts or addresses can access the data. Contract state variables and functions have a slight difference that we're going to check out. I want to mention that accessibility and visibility are different things in blockchain development context.
Solidity is an object-oriented language to write smart contracts that can be deployed on the blockchain, for instance, Ethereum. The syntax is similar to Javascript, but on the other hand, semantics is closer to C++. We will dig into Solidity language structure and functions from a Swift developer's perspective.
We learned how to add a sidebar for an iPad in the previous blog post, but that approach isn't that great for an iPhone. It looks pretty weird, and once we configure a default view, it automatically navigates to it once iPhone app starts. This isn't great on a phone but makes total sense on an iPad. We can improve that by showing a sidebar for an iPad and a TabView on an iPhone.
Starting with iPadOS 14, Apple has redesigned the iPad sidebar by making it easier to navigate within an app. They are explaining that in the Human Interface Guidelines. They are already using that in apps such as Photos, Files, Notes, Calendar, and more. This time let's check out how we can build a sidebar for iPad using SwiftUI. Currently, sidebar element is available only for iPads in landscape mode.
Using mobile apps, we navigate to another view, calculate business expenses, or send a tweet by tapping on a button. SwiftUI makes it a breeze to construct a button. This time we will talk how to do it in three ways using the view modifier approach, building a custom view modifier, and applying the button style.
We explored the Mapview in SwiftUI a while back. This time we will look into creating custom map annotations, the limitations, and how to overcome some of them. Placing annotations on the map, like marking a specific place, is one of the most critical tasks when showing a map in our iOS applications.
Localizing our applications is more critical than we think. We usually stick with English as the primary language. Only 4.9% of the world’s 7.8 billion inhabitants speak English. Most of the people aren’t native English speakers. In the grand scheme of things, only 360 million people speak English as their first language.
Grid layouts enable us to show views in a grid that expands either vertically or horizontally. We've all seen it, for instance, in the iOS Photos application. Those who have worked with UIKit might recognize it as UICollectionView.
Navigating from one view to another, or simply showing a title and buttons, is one of the most crucial building blocks of modern iOS applications. Almost every app has this feature. SwiftUI brings some new approaches for how to show the Navigation Bar, set the title, and add buttons. So let's check it out.
TabBar is a vital component of iOS and has been from iOS 2.0. This element appears at the bottom of the iOS and iPadOS devices and allows our app users to switch between different views or functions quickly. It is a major element of Apple's apps like Music, Podcasts, and App Store.
Showing and hiding some parts of information is a vital feature in mobile apps, especially considering that phone screens are much smaller than those on laptops or desktop computers. Now with the new SwiftUI capabilities, we can collapse content with DisclosureGroup. Let's see how we could use it in various ways.
Alerts are one of the most crucial building blocks of iOS applications. We can use them to inform users about an error if something takes more time, like downloading a file or ensuring that everything is OK. Another use case with alerts is asking confirmation if our app users want to delete something or make a wire transfer.
This time, we will look at several ways to show a text label inside a circle using SwiftUI. We will dig deeper into three different ways using the ZStack view and .background and .overlay modifiers. As a small bonus, we will check out how to present a text label over a circle using the .clipShape modifier.
Selecting images from our iPhone library is needed when changing a profile picture, posting an update, or sharing the photo of your pet. In this post, we are going to look into how to use PHPickerViewController with SwiftUI. Apple announced this view controller at WWDC2020.
Once you create a SwiftUI view, it has the default background color. White for light mode and black for dark mode respectively. But how to change it to something different? Let's look into that today.
When presenting a small piece of extra information on the screen, showing a modal view is essential. With UIKit, we could do this with presentViewController:animated:completion: function. However, using SwiftUI, we need to twist our thinking towards using view or environment state, as the modal view is now called a sheet.
Launch Screen is the first interaction that users see when using our apps. That's why investing time in making our app launch screens feel responsive and visually appealing is important. We are playing with the perceived time and it can be a great first impression.
A while back we looked into dynamic type with the system font. This time we are going to check out how to use the dynamic type with a custom font in our iOS apps. Apple provides great APIs to make our apps accessible even if we're using custom font styles.
Finding places, navigating our way, or simply checking what's around - these are essential things that smartphones can help with. This year Apple added maps functionality to the SwiftUI framework. Let's check out how we can use it and what are the current problems.
Every year the third Thursday of May is the Global Accessibility Awareness Day. This time I want to focus on Dynamic Type in our iOS, iPadOS, and macOS projects. By implementing font scaling we can improve lives for loads of people with disabilities and impairments.
Swift on the server lately is getting more traction despite IBM leaving the club. One of the most popular frameworks out there is Vapor. It is built on top of Apple’s SwiftNIO and written fully in Swift programming language. This time we will look into how to work with WebSockets using Vapor framework. We are going to see how to create a client and server using Vapor’s module WebSocketKit and Vapor framework itself.
NSTimer or just Timer in Swift world is a commonly used way to execute something repeatedly with an interval. For instance, a countdown timer is a perfect example. A hidden gem is CADisplayLink - a special flavor of timer that is linked to the device screen refresh rate. Usually, it is 60 frames per second, but in new iPads, it is 120 frames per second.
Opening and keeping a WebSocket connection alive isn't enough when dealing with it. The connection needs to be closed either from user or sever side. That is mentioned in the official WebSocket protocol.
Caching and invalidating cache is one of the hardest things in computer science according to Martin Fowler. Recently I was dealing with cache and invalidating it in three of my applications. I had some serious issues with that and wanted to dig deeper. This time we will discuss URLRequest caching strategies and how to use it in your apps. I will share some of my learnings and problems that I found.
In previous articles, we discussed how to get started with and use subscriptions with GraphQL in iOS (and iPadOS, tvOS, and macOS) using Swift programming language.
GraphQL main functionality is to fetch and update data from the server. In addition to that subscriptions allow us to listen and to send messages from and to server in real-time. It is similar to regular queries, but the answer will be received when an event happens either on the server or on the client. Apollo iOS SDK library supports subscriptions and it is powered by the Swift WebSocket library Starscream behind the scenes to connect to the server. Let's look at how to set it up and start using it.
Apple PassKit framework is responsible for Apple Pay and managing user passes in Wallet app. This time let’s talk about passes, how to create and distribute them. Wallet app allows iOS users to organize boarding passes, tickets or gifts, business and loyalty cards. In short, passes are digital representations of information that usually is printed on paper or used as plastic cards.
I am an Apple fanboy and I admit that. But one of the most frustrating things in being an app developer is dealing with the App Store review and compliance teams. This time I would like to share my experience with these problems.
GraphQL is an alternative to the commonly used REST API approach. When using GraphQL you only get one single endpoint to the server and through that endpoint you need to specify the exact data you need. It was created by Facebook in 2012 and open-sourced in 2015.
Websockets in iOS 13, macOS 10.15, tvOS 13, watchOS 6 and Mac Catalyst have gained first-class citizen status in networking stack. Apple has finally added support in URLSession and for lower level in Network.framework for their platforms. This time we will focus on implementing Websockets using URLSession capabilities.
This year I finally had a chance to attend WWDC (Apple Worldwide Developers Conference). It has always been my dream to go there and see the Keynote, conference and all other events with my own eyes.
Here's something useful to know - UIView’s are backed by CALayer’s. Layers offer a lower-level interface to the visual content. When we need more flexibility or performance, we can go to layer level.
Animation has been an important part of the Mac OS X user interface since the very beginning. You’ve probably seen the Genie effect, which occurs when you minimize an application, so many times that you hardly notice it anymore. Apple integrates animation into its operating systems and applications, and it is becoming so commonplace that users are starting to expect it. Core Animation is a group of features that makes it easy to build animated user interfaces for the Apple ecosystem devices like iPhone, iPad, Apple TV, and Mac.
Animating a UIBezierPath drawing is a pretty trivial task. But how to animate shape morphing, i.e. make one shape change into another? (For instance, morphing a triangle into a square.) To accomplish this, we need to use CAShapeLayer and animate its properties using Core Animation capabilities.
WebSockets allow for extremely fast two-way networking communication, which lets you send and receive updates quicker and more often, not to mention securely. WebSocket is a communication protocol that uses sockets, providing duplex communication over a single TCP connection. It was standardized by the IETF in 2011 and is a different protocol from HTTP.