Rob Kerr's Blog (Page 2)

Sign in Subscribe

Swift Closures Cheat Sheet

General Notes * Closures are reference types * Global functions are closures that have names and capture no values * Closures are commonly used as callback functions for network API requests * The parameter to the .sorted() and .sort() functions accept closures--which illustrates that closures can also be used in non-asynchronous code. * Closures can

A visual reference to SwiftUI DatePicker styling for iOS and macOS

Each section below provides a snippet of code that configures a particular DatePicker, followed by the UI component created by iOS and macOS output for the specific component configuration. -- Some SwiftUI styles are not available on both iOS and macOS. For example the Wheel style is iOS only; the

Creating an iOS bar chart in code using Swift and UIKit

In this post, I'll build a simple bar chart in code, and add it to a the default UIViewController created by an Xcode template project. The techniques you'll learn in this article are: * Creating a UIView entirely in code * Adding Auto Layout constraints to views in the hierarchy using code

Swift Strings Cheat Sheet

Constructing Strings String from Literal let str = "Hello, dog!" let str2 = "Hello, 🐶!" Including Escaped Characters print("Backslash: \\") print("Tab: \t") print("LF: \nThis is on the next line") print ("CR\r") print("Single Quote: \'") print("Double Quote: \"") print("Unicode Scalar: \u{1F436}") // output: Backslash: \ Tab: LF: This is on

Using automatic API request retries make iOS apps more resilient

This technique is demonstrated within the context of a SwiftUI application, but the real topic of discussion is the NetworkClient singleton used by the SwiftUI app. There's really no difference between how this technique applies for UIKit or AppKit, so it should still be relevant. App Architecture The overall app

Swift Dictionary Cheat Sheet

Dictionary Fundamentals A Dictionary, provided by Foundation, is a type of hash table that stores key/value pairs. * Keys must conform to Hashable * Access to elements is O(1) * Derived from NSDictionary Best used for key/value storage where lookup by key is the primary use case. However, Apple has

Using DispatchGroup in SwiftUI

This post covers how to use the Grand Central Dispatch's DispatchGroup object to coordinate separate web requests so that UI updates can be completed at the same time, even when asynchronous requests aren't guaranteed to return in a predictable order. This post is primarily a tutorial of using GCD's DispatchGroup,

Sorting collections of custom types using higher order functions in Swift

This post is a cheat sheet for sorting sequences of custom objects using Swift's sort operators. While sorting simple types (String, Int) are covered well in Apple's documentation on the subject and in many other places, I've focused below on sorting custom object types, which is more relevant to my

Swift high-order reduce usage with custom types

What is Reduce? Map is a general term that has roots in other technologies (such as Hadoop big data processing, which is where I've used it before 🙂). Reduce means to iterate over a sequence of objects, and perform some operation on each one, returning some summary value computed from the

Swift high-order map usage with custom types

What is Map? Map is a term that has roots in other technologies (such as Hadoop big data processing, which is where I've used it before 🙂). Map means to iterate over a sequence of objects, and perform some operation on each one, returning a new sequence of objects as the

Capture a UIView as image using Swift

This technique demonstrates the simple but useful task of capturing the contents of a UIView as a JPEG image data object. The resulting Data object can be written to a .jpg file, uploaded to a web service, or sent as an e-mail attachment (as is covered in this related post)

Sending Email with Image Attachments in Swift

Sending content from an iOS application to external sources like email is a common requirement. This quick post summarizes the steps to implement this feature. Aa an added twist, the project used for this technique post includes capturing an image from one of the app's UIViews. Demonstration of iOS App

Drawing with Core Graphics using Swift

This technique illustrates a mid-level technique: implementing custom Core Graphics drawing in a UIView. Often a custom effect in a View can be implemented by adding subviews and positioning them with constraints. But other times, you just need to take over and draw what you need. In those cases--CoreGraphics to

iOS Image Caching for UIKit Apps

The most common approach to displaying images in an iOS application is to include images in asset catalogs compiled into and shipped with the app. For images that are provided at design time and never change, this is nearly always the best approach. There are some scenarios where bundling images