Extracting members of a collection that match some filtering predicate is a common pattern in programming. Traditionally we would iterate over all members (e.g. with a for or foreach loop), and save each member matching some condition. Most programming languages now provide some single step filter function to eliminate …

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It's helpful to experiment with language syntax in a REPL tool before pasting code into your editor. REPL is an acryonym for Read, Evaluate, Print, Loop. REPL tools are simple interactive programming environments primarily used to validate syntax and algorithms. Swift The main Swift REPL tool is the Playground feature …

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Firebase Authentication supports built-in and custom user claims that allow us to conditionally expose functionality to users based on authorization groups. This post demonstrates the syntax to add custom claims in a Firebase backend, and read claims from mobile apps. What are Claims? In identity systems, a …

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A core feature of all programming languages is the trusty for loop. For loops execute a statement a predefined number of times with some way to exit the loop early. Swift Swift uses range operators to construct simple for loops. 1let start = 0 2let end = 10 3 4for i in start ... end { 5 print(i) // prints 0 through 10 …

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When creating a GET URLRequest in Swift, it's often necessary to URL encode GET string parameters. Many languages include String functions to emit url encoded versions of Strings, but as of this writing Swift does not fully address this problem in the Foundation String class. However, Swift Foundation actually does …

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Most modern languages support the ability for asynchronous function calls to be called from synchronous code blocks. This language feature is usually called async/await. This post is a brief syntax scratchpad comparing async/await in different languages. Swift In Swift, an await-able async function is created by adding …

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Swift Playgrounds in Xcode are super useful for trying out Swift syntax either for learning, or for refining code before incorporating it into a real project. By default async functions can't be executed in a playground, but it is possible. Here's an example: 1import Foundation 2import _Concurrency 3import …

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ForEach is a common pattern in programming modern programming languages. Prior to ForEach, the standard approach to iterating over an array of objects was to use a for loop stepping from the first index to the last. ForEach syntax has extra utility in languages that support many types of collections: a list iterated …

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Beginning in iOS 15 and macOS 13, Swift developers can begin using the Swift async/await syntax to to suspend and resume processing while waiting for long-running work to complete. This post walks through the process to upgrade a set of nested API calls from the familiar closure syntax to the new and improved Swift …

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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 …

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