Chart structure
Help your agent structure charts and surrounding views to avoid updates that do not affect the chart.
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Performant Swift Charts
Improve rendering and interaction performance by structuring charts and surrounding views to limit unnecessary updates and use Swift Charts APIs effectively.
What your agent can improve
Rendering performance
Identify API choices that introduce unnecessary rendering work and give your agent guidance to address them.
Responsive interactions
Find interaction state changes that trigger unnecessary chart updates, helping your agent keep interactions responsive.
Issues Performant Swift Charts flags
Performant Swift Charts flags over 70 issues in your code. Each finding arrives at the line where the issue occurs, with the guidance and code example written for that case.
- Missing measurements replaced with zero
- Lines and areas without series identity or a defined order
- A Chart built inside a larger view body instead of a dedicated view
- Selection state that re-evaluates the whole chart
- Selection resolved by scanning the plotted data
- Value labels that change per observation
- Per-mark work repeated inside chart content
- Bars on a date or number axis without a unit or bins
- @Environment read inside custom ChartContent
- A parent's animation reaching the chart
Token efficiency
Your agent skips millions of tokens of reasoning and reads guidance only for the issues flagged.
Cross-file insight
Follows your view hierarchy across files and presentations, beyond single views and functions.
Deep knowledge
Built on our books and articles, and Natalia's work on Apple's SwiftUI team.
Example findings
These examples show the patterns SwiftFairy flags and the guidance your agent can use to address them. Highlighted lines mark the code to review; each finding indicates whether the guidance is a requirement, recommendation, or consideration.
Consider
Preserve missing-data semantics
When a measurement is missing, substituting zero changes what the chart communicates. The appropriate representation depends on whether the chart draws independent marks or connects neighboring observations.
Pattern flagged for review
BarMark(
x: .value("Date", reading.date),
y: .value(
"Temperature",
reading.temperature ?? 0
)
)
AreaMark(
x: .value("Date", reading.date),
y: .value(
"Temperature",
reading.temperature ?? 0
)
)
A possible improvement
if let temperature = reading.temperature {
BarMark(
x: .value("Date", reading.date),
y: .value(
"Temperature",
temperature
)
)
}
AreaMark(
x: .value("Date", reading.date),
y: .value(
"Temperature",
reading.temperature ?? Double.nan
)
)
For independent bars, omit the mark when its measurement is missing. For an area chart, retain the observation and use Double.nan for the missing value to break the area across the gap. Removing the observation would connect its neighbors.
Consider
Use consistent semantic labels
When observations represent the same variable, their semantic label should remain consistent. Each observation's value belongs in the second argument to .value, rather than being interpolated into its label.
Pattern flagged for review
BarMark(
x: .value("Date", reading.date),
y: .value("Temperature", reading.temperature)
)
.foregroundStyle(by:
.value(
"Status \(reading.status)",
reading.status
)
)
A possible improvement
.foregroundStyle(
by: .value("Status", reading.status)
)
Use a consistent dimension label and pass the observation's status as the value. Whether a dynamic label is appropriate depends on the intended semantics.
…and over 70 other issues.
Put the findings to work
Ask your agent to review a code change or a complete codebase with SwiftFairy. Your agent uses the findings and their accompanying code examples to resolve issues in your code.
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