The September issue of the Nil Coalescing newsletter is out 📬 It includes an introduction to SwiftFairy, our Mac app that helps coding agents review Swift and SwiftUI code, plus iOSDevUK highlights and this month's articles: nilcoalescing.com/newsletter/2...

Nil Coalescing - Nil Coalescing Newsletter – September 2026

We've released SwiftFairy, our new Mac app that helps coding agents review Swift and SwiftUI code. This month also took us to Wales for iOSDevUK, where Matt presented on interactive Swift Charts and I...

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SwiftFairy 2026.9.2 is out. Large audits now take seconds, not minutes, and use far less of your agent's context. The video shows a pattern I've noticed agents often write: Binding(get:set:) in a view body, and the labeled subscript SwiftFairy steers them to. tools.nilcoalescing.com/swiftfairy

Most heatmaps use rectangular grids, but with Swift Charts we can use PointPlots to arrange cells with alternative shapes. In my new post, we explore hexagonal cells for spatial data. nilcoalescing.com/blog/Visuali... #iOSDev #SwiftUI #SwiftLang

Visualising data with a hexagonal heatmap in Swift Charts

Explore alternatives to rectangular heatmap cells for visualising spatial data along coastlines and irregular boundaries.

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If, like me, you were wondering how to show the slider to control the hinge angle in the iPhone Duo simulator in Xcode 27.1, we need to hold the Option key to reveal it 🙂

SwiftFairy 2026.9.1 is out! 🧚 SDK and project lookups are more reliable, and the complexity limits are much higher, so those huge views we all have get a proper review rather than just "too complex, please break it up". Release notes: tools.nilcoalescing.com/swiftfairy/r... #iOSDev #SwiftUI

Besides reviewing code, I've been using SwiftFairy while building new features. Asking the agent to check SwiftFairy before working on Swift or SwiftUI code allows it to pull in relevant examples for the APIs it's about to use. tools.nilcoalescing.com/swiftfairy/h... #iOSDev #SwiftUI #SwiftLang

SwiftFairy - How to Use

Install SwiftFairy, activate Scroll access, connect a coding agent, and review Swift and Apple API usage.

tools.nilcoalescing.com

We've had many questions about how SwiftFairy, our new code review app for Swift and SwiftUI, compares to skills and fits into an agent workflow. I've written a post explaining how agents work with it and why it's more reliable: nilcoalescing.com/blog/Introdu... #SwiftUI #AICoding #iOSDev

Introducing SwiftFairy: Swift and SwiftUI code reviews for coding agents

SwiftFairy brings our Swift and SwiftUI expertise to your coding agent, running static analysis on your Mac over MCP and returning targeted guidance for each flagged issue.

nilcoalescing.com

Control how SwiftUI presents toolbar items and tabs on iPhone Duo with the new iOS 27.1 APIs, from arranging custom labels to prioritizing actions when space is limited: nilcoalescing.com/blog/Configu... #iOSDev #SwiftUI

Configuring SwiftUI toolbars on iPhone Duo

Control how SwiftUI presents toolbar items and tabs on iPhone Duo with the new iOS 27.1 APIs, from arranging custom labels to prioritizing actions when space is limited.

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Sometimes we want a gradient to span the whole plot rather than restart within each mark. In Swift Charts, alignsMarkStylesWithPlotArea(true) gives marks a shared gradient alignment. Learn more in our book, Swift Charts Beyond the Basics: books.nilcoalescing.com/swift-charts... #iOSDev #SwiftUI

I’ve been trying to turn our articles and books into skills, but agents struggle to navigate them and forget rules they just read. So we ended up building SwiftFairy to detect issues and attach guidance inline, so agents no longer need to recall it all. tools.nilcoalescing.com/swiftfairy/ #iOSDev

SwiftFairy

A macOS app that locally reviews your agent's Swift and SwiftUI code and provides guidance to fix issues.

tools.nilcoalescing.com

We've released a new developer tool! SwiftFairy is a native Mac app that reviews your AI agent's Swift and SwiftUI code locally on device and provides focused guidance and improvement suggestions. Excited for you to try it out! tools.nilcoalescing.com/swiftfairy #iOSDev #SwiftLang #SwiftUI

SwiftFairy

A macOS app that locally reviews your agent's Swift and SwiftUI code and provides guidance to fix issues.

tools.nilcoalescing.com

Use the AttributedString API to build a reusable Text initializer in SwiftUI that applies a distinct font to the unit component of a formatted measurement: nilcoalescing.com/blog/Styling... #iOSDev #SwiftUI

Styling measurement unit fonts in SwiftUI

Use the AttributedString API to build a reusable Text initializer that applies a distinct font to the unit component of a formatted measurement.

nilcoalescing.com

Sometimes we want a gradient to span the whole plot rather than restart within each mark. In Swift Charts, alignsMarkStylesWithPlotArea(true) gives marks a shared gradient alignment. Learn more in our book, Swift Charts Beyond the Basics: books.nilcoalescing.com/swift-charts... #iOSDev #SwiftUI

Build SwiftUI views that update periodically or continuously, without relying on explicit state changes, to create dynamic interfaces and visual effects: nilcoalescing.com/blog/Timelin... #iOSDev #SwiftUI

Refreshing and animating views using TimelineView in SwiftUI

Build SwiftUI views that update periodically or continuously, without relying on explicit state changes, to create dynamic interfaces and visual effects.

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"The SwiftUI Way" has been updated with expanded guidance on SwiftUI data flow, view updates, and performance, including changes introduced in Xcode 27: nilcoalescing.com/blog/TheSwif... #iOSDev #SwiftUI

"The SwiftUI Way" book update: expanded guidance on data flow and performance

'The SwiftUI Way' has been updated with expanded guidance on SwiftUI data flow, view updates, and performance, including changes introduced in Xcode 27.

nilcoalescing.com

Reorder items within and between custom SwiftUI containers, and build selection-aware multi-item drag and drop interactions with the new APIs in iOS 27: nilcoalescing.com/blog/NewSwif... #iOSDev #SwiftUI

New SwiftUI APIs for reordering and drag and drop on iOS 27

Reorder items within and between custom SwiftUI containers, and build selection-aware multi-item drag and drop interactions with the new APIs in iOS 27.

nilcoalescing.com

I've started looking into the new SwiftUI APIs for iPhone Duo in Xcode 27.1 and wrote a post on configuring toolbars, adapting custom labels, and prioritizing toolbar actions or tabs when space is limited: nilcoalescing.com/blog/Configu... #iOSDev #SwiftUI

Configuring SwiftUI toolbars on iPhone Duo

Control how SwiftUI presents toolbar items and tabs on iPhone Duo with the new iOS 27.1 APIs, from arranging custom labels to prioritizing actions when space is limited.

nilcoalescing.com

Just got back from our trip to Wales for iOSDevUK! It was lovely to catch up with everyone and learn from so many great talks. I also really enjoyed running my SwiftUI workshop and seeing everyone excited to dig deeper into SwiftUI, with lots of thoughtful questions and discussions 👩‍💻

To diagnose performance issues caused by the structure of ForEach content in SwiftUI's List and lazy stacks, we can enable slow-path logging in Xcode. My new post shows how to set it up, interpret the diagnostic messages, and address the reported issues: nilcoalescing.com/blog/Diagnos... #iOSDev

Diagnosing ForEach performance issues in SwiftUI lazy containers

Learn how to enable SwiftUI's ForEach slow-path diagnostic in Xcode, interpret warnings about variable view counts, and address the reported patterns in List and lazy stacks.

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💡 𝐵𝑢𝑖𝑙𝑑𝑖𝑛𝑔 𝑎 𝑠𝑢𝑛𝑏𝑢𝑟𝑠𝑡 𝑑𝑖𝑎𝑔𝑟𝑎𝑚 𝑖𝑛 𝑆𝑤𝑖𝑓𝑡 𝐶ℎ𝑎𝑟𝑡𝑠 by Matthaus Woolard (@hishnash.bsky.social) Swift Charts can build a proper sunburst diagram, but the fun is in the details: 𝑆𝑒𝑐𝑡𝑜𝑟𝑀𝑎𝑟𝑘 rings, radius ratios, angular insets, grouped data layout… #iOSDev nilcoalescing.com/blog/Buildin...

Building a sunburst diagram in Swift Charts

Swift Charts can build a proper sunburst diagram, but the fun is in the details: `SectorMark` rings, radius ratios, angular insets, grouped data layout, and accessibility labels that don’t get treated as an afterthought. The result is a multi-level donut chart where the outer rings still line up with their parent categories, which sounds simple until you try to fake it by hand. Who doesn’t like a chart that looks custom without becoming a pile of custom drawing code? This is a good reminder that Charts has more range than the usual bar-and-line dashboard screenshots suggest.

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Control which SwiftUI toolbar actions stay visible, move commands into overflow, pin an important item and configure navigation bar minimization with the new iOS 27 APIs: nilcoalescing.com/blog/Adaptiv... #iOSDev #SwiftUI

Adaptive SwiftUI toolbars in iOS 27

Control which SwiftUI toolbar actions stay visible, move commands into overflow, pin an important item and configure navigation bar minimization with the new iOS 27 APIs.

nilcoalescing.com

Learn how alignment guides position views in SwiftUI, how to override a built-in guide, and how to define a custom alignment for views in nested containers: nilcoalescing.com/blog/Alignme... #iOSDev #SwiftUI

Alignment guides in SwiftUI

Learn how alignment guides position views in SwiftUI, how to override a built-in guide, and how to define a custom alignment for views in nested containers.

nilcoalescing.com

Sometimes we want a chart’s domain to include a value beyond our data. Rather than setting an explicit domain, we can append it to the values Swift Charts uses to infer one. Explore more in our new book, Swift Charts Beyond the Basics: books.nilcoalescing.com/swift-charts... #iOSDev #SwiftUI

Present grouped data as a multi-level donut chart in Swift Charts, where each outer ring reveals a more detailed breakdown and each subgroup aligns with its parent category: nilcoalescing.com/blog/Buildin... #iOSDev #macOSDev #SwiftUI

Building a sunburst diagram in Swift Charts

Present grouped data as a multi-level donut chart, where each outer ring reveals a more detailed breakdown and each subgroup aligns with its parent category.

nilcoalescing.com

Build an interactive bar chart in Swift Charts that displays detailed annotations when the user is hovering over bar marks: nilcoalescing.com/blog/ChartAn... #macOSDev #SwiftUI

Show chart annotations on hover in Swift Charts

Build an interactive bar chart in Swift Charts that displays detailed annotations when the user is hovering over bar marks.

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Authors: Max Desiatov, @mecid.bsky.social, @emredeg.bsky.social, Apple Documentation, @hishnash.bsky.social, @natpanferova.bsky.social, @lucas.love, @nobodywhooo.bsky.social. Never miss an issue → subscribe: ios-newsletter.snappmobile.io/subscribe

Another great chart tutorial by @hishnash.bsky.social, this time it's on how to build a sunburst diagram in Swift Charts, with multiple levels of hierarchical data arranged into concentric rings: nilcoalescing.com/blog/Buildin... #iOSDev #macOSDev #SwiftUI

Building a sunburst diagram in Swift Charts

Present grouped data as a multi-level donut chart, where each outer ring reveals a more detailed breakdown and each subgroup aligns with its parent category.

nilcoalescing.com

When a dataset contains many observations, grouping them into broader categories can make patterns easier to see. Learn how to build a sunburst diagram with Swift Charts to show both the groups and the detail within them. nilcoalescing.com/blog/Buildin... #iOSDev #SwiftUI #SwiftLang

Building a sunburst diagram in Swift Charts

Present grouped data as a multi-level donut chart, where each outer ring reveals a more detailed breakdown and each subgroup aligns with its parent category.

nilcoalescing.com

Learn how to use matchedGeometryEffect() in SwiftUI to animate a capsule background that highlights the selected option in a custom segmented control: nilcoalescing.com/blog/CustomS... #iOSDev #macOSDev #SwiftUI

SwiftUI matched geometry effect in a custom segmented control

Learn how to use matchedGeometryEffect() in SwiftUI to animate a capsule background that highlights the selected option in a custom segmented control.

nilcoalescing.com

When a dataset contains many observations, grouping them into broader categories can make patterns easier to see. Learn how to build a sunburst diagram with Swift Charts to show both the groups and the detail within them. nilcoalescing.com/blog/Buildin... #iOSDev #SwiftUI #SwiftLang

Building a sunburst diagram in Swift Charts

Present grouped data as a multi-level donut chart, where each outer ring reveals a more detailed breakdown and each subgroup aligns with its parent category.

nilcoalescing.com