axiom-swift-modern

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English

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Chinese

Modern Swift Idioms

现代Swift惯用写法

Purpose

用途

Claude frequently generates outdated Swift patterns from its training data. This skill corrects the most common ones — patterns that compile fine but use legacy APIs when modern equivalents are clearer, more efficient, or more correct.

Philosophy: "Don't repeat what LLMs already know — focus on edge cases, surprises, soft deprecations." (Paul Hudson)

Claude的训练数据中经常会生成过时的Swift代码模式。本指南用于修正最常见的这类问题——这些模式虽然可以正常编译，但使用了遗留API，而对应的现代等效写法更清晰、更高效或者更准确。

理念：「不要重复LLM已经知道的内容——聚焦边界场景、意外问题、软废弃特性。」（Paul Hudson）

Modern API Replacements

现代API替换

Old Pattern	Modern Swift	Since	Why
`Date()`	`Date.now`	5.6	Clearer intent
`filter { }.count`	`count(where:)`	5.0	Single pass, no intermediate allocation
`replacingOccurrences(of:with:)`	`replacing(_:with:)`	5.7	Swift native, no Foundation bridge
`CGFloat`	`Double`	5.5	Implicit bridging; exceptions: optionals, inout, ObjC-bridged APIs
`Task.sleep(nanoseconds:)`	`Task.sleep(for: .seconds(1))`	5.7	Type-safe Duration API
`DateFormatter()`	`.formatted()` / `FormatStyle`	5.5	No instance management, localizable by default
`String(format: "%.2f", val)`	`val.formatted(.number.precision(.fractionLength(2)))`	5.5	Type-safe, localized
`localizedCaseInsensitiveContains()`	`localizedStandardContains()`	5.0	Handles diacritics, ligatures, width variants
`"\(firstName) \(lastName)"`	`PersonNameComponents` with `.formatted()`	5.5	Respects locale name ordering
`"yyyy-MM-dd"` with DateFormatter	`try Date(string, strategy: .iso8601)`	5.6	Modern parsing (throws); use "y" not "yyyy" for display
`contains()` on user input	`localizedStandardContains()`	5.0	Required for correct text search/filtering

旧写法	现代Swift写法	起始版本	原因
`Date()`	`Date.now`	5.6	意图更清晰
`filter { }.count`	`count(where:)`	5.0	单次遍历，无中间内存分配
`replacingOccurrences(of:with:)`	`replacing(_:with:)`	5.7	Swift原生实现，无需Foundation桥接
`CGFloat`	`Double`	5.5	隐式桥接；例外情况：可选值、inout参数、ObjC桥接API
`Task.sleep(nanoseconds:)`	`Task.sleep(for: .seconds(1))`	5.7	类型安全的Duration API
`DateFormatter()`	`.formatted()` / `FormatStyle`	5.5	无需实例管理，默认支持本地化
`String(format: "%.2f", val)`	`val.formatted(.number.precision(.fractionLength(2)))`	5.5	类型安全，支持本地化
`localizedCaseInsensitiveContains()`	`localizedStandardContains()`	5.0	支持变音符号、连字、宽度变体处理
`"\(firstName) \(lastName)"`	配合 `.formatted()` 使用 `PersonNameComponents`	5.5	遵循地区姓名排序规则
`"yyyy-MM-dd"` 搭配 DateFormatter	`try Date(string, strategy: .iso8601)`	5.6	现代解析能力（支持抛出异常）；展示场景请使用"y"而非"yyyy"
对用户输入调用 `contains()`	`localizedStandardContains()`	5.0	正确实现文本搜索/过滤的必要写法

Modern Syntax

现代语法

Old Pattern	Modern Swift	Since
`if let value = value {`	`if let value {`	5.7
Explicit `return` in single-expression	Omit `return` ; `if` / `switch` are expressions	5.9
`Circle()` in modifiers	`.circle` (static member lookup)	5.5
`import UIKit` alongside `import SwiftUI`	Often not needed — SwiftUI re-exports most UIKit/AppKit types. Retain for UIKit-only APIs ( `UIApplication` , etc.)	5.5

旧写法	现代Swift写法	起始版本
`if let value = value {`	`if let value {`	5.7
单表达式中显式写 `return`	省略 `return` ； `if` / `switch` 属于表达式	5.9
修饰符中写 `Circle()`	`.circle` （静态成员查找）	5.5
同时 `import UIKit` 和 `import SwiftUI`	通常不需要——SwiftUI会重新导出大部分UIKit/AppKit类型。仅在使用UIKit专属API（如 `UIApplication` 等）时保留导入	5.5

Foundation Modernization

Foundation现代化

Old Pattern	Modern Foundation	Since
`FileManager.default.urls(for: .documentDirectory, ...)`	`URL.documentsDirectory`	5.7
`url.appendingPathComponent("file")`	`url.appending(path: "file")`	5.7
`books.sorted { $0.author < $1.author }` (repeated)	Conform to `Comparable` , call `.sorted()`	—
`"yyyy"` in date format for display	`"y"` — correct in all calendar systems	—

旧写法	现代Foundation写法	起始版本
`FileManager.default.urls(for: .documentDirectory, ...)`	`URL.documentsDirectory`	5.7
`url.appendingPathComponent("file")`	`url.appending(path: "file")`	5.7
重复使用 `books.sorted { $0.author < $1.author }`	遵循 `Comparable` 协议，直接调用 `.sorted()`	—
展示用日期格式中写 `"yyyy"`	`"y"` ——在所有日历系统中都正确	—

SwiftUI Convenience APIs Claude Misses

Claude遗漏的SwiftUI便捷API

ContentUnavailableView.search(text: searchText)
(iOS 17+) automatically includes the search term — no need to compose a custom string
LabeledContent
in Forms (iOS 16+) provides consistent label alignment without manual HStack layout
confirmationDialog()
must attach to triggering UI — Liquid Glass morphing animations depend on the source element

ContentUnavailableView.search(text: searchText)
（iOS 17+）自动包含搜索词——无需手动拼接自定义字符串
表单中的
LabeledContent
（iOS 16+）无需手动写HStack布局即可实现一致的标签对齐效果
confirmationDialog()
必须挂载到触发的UI元素上——毛玻璃变形动画依赖源元素定位

Common Claude Hallucinations

Claude常见幻觉

These patterns appear frequently in Claude-generated code:

Creates
DateFormatter
instances inline — Use
```
.formatted()
```
or
```
FormatStyle
```
instead. If a formatter must exist, make it
```
static let
```
.

Uses
DispatchQueue.main.async
— Use

@MainActor

MainActor.run

. Never GCD. (See

axiom-swift-concurrency

for full guidance.)

Uses
CGFloat
for SwiftUI parameters —
```
Double
```
works everywhere since Swift 5.5 implicit bridging.
Generates
guard let x = x else
— Use
```
guard let x else
```
shorthand.
Returns explicitly in single-expression computed properties — Omit
```
return
```
.

这些模式在Claude生成的代码中频繁出现：

内联创建
DateFormatter
实例——请改用
```
.formatted()
```
或
```
FormatStyle
```
。如果必须使用formatter，请声明为
```
static let
```
。
使用
DispatchQueue.main.async
——请使用
```
@MainActor
```
或
```
MainActor.run
```
，永远不要使用GCD。（完整指南请参考
```
axiom-swift-concurrency
```
）
SwiftUI参数使用
CGFloat
——自Swift 5.5隐式桥接支持以来，
```
Double
```
可在所有场景下正常使用。
生成
guard let x = x else
写法——请使用
```
guard let x else
```
简写。
单表达式计算属性中显式写return——省略
```
return
```
即可。

Resources

资源

Skills: axiom-swift-performance, axiom-swift-concurrency, axiom-swiftui-architecture

相关技能：axiom-swift-performance, axiom-swift-concurrency, axiom-swiftui-architecture