ios - Xcode 重构 "Convert to Switch"

Question

Xcode Refactor 有一个名为“转换为 Switch”的功能。我正在寻找可以由函数使用并转换为 switch 流语句的代码示例。

Answer 1

更新

正如您所指出的，转换为 Switch != 转换为 Switch 语句。为了理解其中的原因，我们需要了解 Xcode 重构功能在幕后是如何工作的。

我发现了什么:

这是一篇关于该主题的精彩文章: https://levelup.gitconnected.com/uncovering-xcode-indexing-8b3f3ff82551

它向我们指出了一个 swift 开源存储库:https://github.com/apple/swift

Xcode 重构是通过 SourceKit 框架完成的，该框架位于 swift 存储库内。

这是与 Xcode 通信的 SourceKit 协议(protocol):https://github.com/apple/swift/blob/main/tools/SourceKit/docs/Protocol.md

在内部，当我们选择“重构”时，Xcode会以某种方式(通过 XPC)发送某些内容，例如 source.request.workspace.refactoring 消息到 SourceKit。并且某处有一个“索引文件”，因此 SourceKit 可以立即(不是在 5 分钟内:))向您建议对于当前代码片段来说足够/可能的选项。

我已经从 github 加载了 swift 存储库(大约 30MB)，导航到 SourceKit 代码并尝试查找与 source.request.workspace 相关的内容.重构.

代码中的某处引用了 swift/IDE/RefactoringKinds.def。我将复制粘贴此文件的内容:

#ifndef REFACTORING
#define REFACTORING(KIND, NAME, ID)
#endif

#ifndef SEMANTIC_REFACTORING
#define SEMANTIC_REFACTORING(KIND, NAME, ID) REFACTORING(KIND, NAME, ID)
#endif

#ifndef RANGE_REFACTORING
#define RANGE_REFACTORING(KIND, NAME, ID) SEMANTIC_REFACTORING(KIND, NAME, ID)
#endif

#ifndef INTERNAL_RANGE_REFACTORING
#define INTERNAL_RANGE_REFACTORING(KIND, NAME, ID) RANGE_REFACTORING(KIND, NAME, ID)
#endif

#ifndef CURSOR_REFACTORING
#define CURSOR_REFACTORING(KIND, NAME, ID) SEMANTIC_REFACTORING(KIND, NAME, ID)
#endif

/// Rename and categorise the symbol occurrences at provided locations
/// (syntactically).
REFACTORING(GlobalRename, "Global Rename", rename.global)

/// Categorize source ranges for symbol occurrences at provided locations
/// (syntactically).
REFACTORING(FindGlobalRenameRanges, "Find Global Rename Ranges", rename.global.find-ranges)

/// Find and categorize all occurences of the file-local symbol at a given
/// location.
REFACTORING(FindLocalRenameRanges, "Find Local Rename Ranges", rename.local.find-ranges)

/// Find and rename all occurences of the file-local symbol at a given
/// location.
CURSOR_REFACTORING(LocalRename, "Local Rename", rename.local)

CURSOR_REFACTORING(FillProtocolStub, "Add Missing Protocol Requirements", fillstub)

CURSOR_REFACTORING(ExpandDefault, "Expand Default", expand.default)

CURSOR_REFACTORING(ExpandSwitchCases, "Expand Switch Cases", expand.switch.cases)

CURSOR_REFACTORING(LocalizeString, "Localize String", localize.string)

CURSOR_REFACTORING(SimplifyNumberLiteral, "Simplify Long Number Literal", simplify.long.number.literal)

CURSOR_REFACTORING(CollapseNestedIfStmt, "Collapse Nested If Statements", collapse.nested.ifstmt)

CURSOR_REFACTORING(ConvertToDoCatch, "Convert To Do/Catch", convert.do.catch)

CURSOR_REFACTORING(TrailingClosure, "Convert To Trailing Closure", trailingclosure)

CURSOR_REFACTORING(MemberwiseInitLocalRefactoring, "Generate Memberwise Initializer", memberwise.init.local.refactoring)

CURSOR_REFACTORING(AddEquatableConformance, "Add Equatable Conformance", add.equatable.conformance)

CURSOR_REFACTORING(ConvertCallToAsyncAlternative, "Convert Call to Async Alternative", convert.call-to-async)

CURSOR_REFACTORING(ConvertToAsync, "Convert Function to Async", convert.func-to-async)

CURSOR_REFACTORING(AddAsyncAlternative, "Add Async Alternative", add.async-alternative)

RANGE_REFACTORING(ExtractExpr, "Extract Expression", extract.expr)

RANGE_REFACTORING(ExtractFunction, "Extract Method", extract.function)

RANGE_REFACTORING(ExtractRepeatedExpr, "Extract Repeated Expression", extract.expr.repeated)

RANGE_REFACTORING(MoveMembersToExtension, "Move To Extension", move.members.to.extension)

RANGE_REFACTORING(ConvertStringsConcatenationToInterpolation, "Convert to String Interpolation", convert.string-concatenation.interpolation)

RANGE_REFACTORING(ExpandTernaryExpr, "Expand Ternary Expression", expand.ternary.expr)

RANGE_REFACTORING(ConvertToTernaryExpr, "Convert To Ternary Expression", convert.ternary.expr)

RANGE_REFACTORING(ConvertIfLetExprToGuardExpr, "Convert To Guard Expression", convert.iflet.to.guard.expr)

RANGE_REFACTORING(ConvertGuardExprToIfLetExpr, "Convert To IfLet Expression", convert.to.iflet.expr)

RANGE_REFACTORING(ConvertToComputedProperty, "Convert To Computed Property", convert.to.computed.property)

RANGE_REFACTORING(ConvertToSwitchStmt, "Convert To Switch Statement", convert.switch.stmt)

// These internal refactorings are designed to be helpful for working on
// the compiler/standard library, etc., but are likely to be just confusing and
// noise for general development.

INTERNAL_RANGE_REFACTORING(ReplaceBodiesWithFatalError, "Replace Function Bodies With 'fatalError()'", replace.bodies.with.fatalError)

#undef CURSOR_REFACTORING
#undef INTERNAL_RANGE_REFACTORING
#undef RANGE_REFACTORING
#undef SEMANTIC_REFACTORING
#undef REFACTORING

如您所见，这里有Convert To Switch Statement，以及Expand Switch Cases，但没有Convert To Switch。

所以我的猜测是，Xcode 在 UI 中向我们展示的内容要么是一个错误(他们忘记删除过时的内容)，要么是当前版本的 Swift 存储库中不存在的某些实现的一部分。

无论如何，你可能会挖得更深 - 我只是试图在短时间内调查它。 :)如果你确实需要这样做，那么除了探索 SourceKit 协议(protocol)之外，我想你可以在 Github 上提出一个问题 - 也许那些知道的人会解释真正的原因。

初始答案

让我们考虑这样一个例子:

enum SomeEnum {
    case option1, option2, option3
}

func convertToSwitchExampleFunc(_ option: SomeEnum) {
    if option == .option1 {
        print("1")
    }
    if option == .option2 {
        print("2")
    }
    if option == .option3 {
        print("3")
    }
}

func callingFunc() {
    convertToSwitchExampleFunc(.option2)
}

如果您选择 convertToSwitchExampleFunc 主体内的所有代码，然后选择 Refactor，Xcode 将不会向您显示“Convert to Switch”。

但是，如果您更改代码，使其更类似于丑陋的“switch”实现(if-else-if-else 链):

func convertToSwitchExampleFunc(_ option: SomeEnum) {
    if option == .option1 {
        print("1")
    }
    else if option == .option2 {
        print("2")
    }
    else if option == .option3 {
        print("3")
    }
}

然后 Xcode 将向您显示“转换为 Switch 菜单”，自动重构的代码将如下所示:

func convertToSwitchExampleFunc(_ option: SomeEnum) {
    switch option {
    case .option1:
        print("1")
    case .option2:
        print("2")
    case .option3:
        print("3")
    default:
        break
    }
}

只是为了提供更多背景信息: