Written by Cihat Gündüz

Description: Swift Charts has come full circle: Get ready to bake up pie and donut charts in your app with the latest improvements to the framework. Learn how to make your charts scrollable, explore the chart selection API for revealing additional details in your data, and find out how enabling additional interactivity can make your charts even more delightful.

Pie Charts

• Pie charts do not have axes, they're: casual, intuitive, approachable
• New mark-based composition syntax type Sector
• Sector is a Position in Polar Coordinate System, size proportional to the value
• By increasing the inner radius, pie chart becomes a donut chart
• To migrate from a bar chart to a pie chart, change BarMark to SectorMark, and argument x: to argument angle:
• Use angularInset: param on SectorMark to create space between pie pieces, supports also .cornerRadius
• Set innerRadius: param on SectorMark to a .ratio value to turn into donut chart (e.g. golden ratio 0.618)
• You can put text inside a donut chart by using .chartBackground which uses GeometryReader

Selection

• Use chartXSelection(value: $selectedValue to store selected value to a @Binding var selectedValue: Value?
• Use if let selectedValue { to define a RuleMark when the value is non-nil to show selection in chart
• Use .annotation modifier on the RuleMark to create a popover that shows additional details about the selection
• Use .overflowResolution param of .annotation and set y: .disabled to extend the annotation outside the chart view

• A variant of .chartXSelection with argument range allows to select a range of values (default: two finger tap on iOS, drag on macOS)
• Use .chartGesture to define a custom gesture for value/range selection

Scrolling

• Enable scrolling via .chartScrollableAxes(.horizontal|.vertical)
• Define scrolling range using .chartXVisibleDomain(length:)
• Store current scroll position in Binding using chartScrollPosition(x: $scrollPosition)
• chartScrollTargetBehavior(.valueAligned(matching:majorAlignment:) allows "snapping" to specific values if needed
• More on scrolling in session Beyond Scroll Views