Swift中如何通过#KeyPath获取类/结构体的变量或方法名？

Hey there! Let's sort out how to grab those property or method names that include "Bar" in Swift. You mentioned trying both Swift 3's #keyPath and Swift 4's simplified approach without luck, so I'll break down working examples for both versions below.

Swift 4 made key paths far more flexible, and you can directly convert them to strings using String(describing:). Plus, if you need to find all members (properties/methods) containing "Bar", we can use Mirror to inspect the type's members.

Example Code #

First, let's define a sample struct with "Bar"-related members:

struct Foo {
    var barProperty: String
    var anotherBar: Int
    func barMethod() {}
    func unrelatedMethod() {}
}

Get a Single Member's Name

For a specific property or method, use a key path and convert it to a string:

// Get property name
let barPropertyKey = \Foo.barProperty
let barPropertyName = String(describing: barPropertyKey) 
// Result: "barProperty"

// Get method name
let barMethodKey = \Foo.barMethod
let barMethodName = String(describing: barMethodKey) 
// Result: "barMethod()"

Filter All Members Containing "Bar"

If you need to find every member with "Bar" (case-insensitive check included here), use Mirror to iterate over the type's children:

let fooInstance = Foo(barProperty: "test", anotherBar: 42)
let mirror = Mirror(reflecting: fooInstance)

// Filter for names containing "Bar" (case-insensitive)
let barRelatedNames = mirror.children.compactMap { child -> String? in
    guard let label = child.label else { return nil }
    return label.lowercased().contains("bar") ? label : nil
}

print(barRelatedNames) 
// Output: ["barProperty", "anotherBar"]

In Swift 3, you use the #keyPath directive to get member names as strings. Note that this requires explicitly referencing each member (you can't automatically enumerate them with just #keyPath, so we still use Mirror for bulk filtering).

Example Code #

struct Foo {
    var barProperty: String
    var anotherBar: Int
    func barMethod() {}
}

// Get single property name
let barPropertyName = #keyPath(Foo.barProperty) 
// Result: "barProperty"

// Get single method name
let barMethodName = #keyPath(Foo.barMethod) 
// Result: "barMethod"

// Filter all "Bar"-related members
let fooInstance = Foo(barProperty: "test", anotherBar: 42)
let mirror = Mirror(reflecting: fooInstance)
let barRelatedNames = mirror.children.flatMap { $0.label }.filter { 
    $0.lowercased().contains("bar") 
}

print(barRelatedNames) 
// Output: ["barProperty", "anotherBar"]

Common Pitfalls to Check #

• Case Sensitivity: Swift is case-sensitive! If your members use lowercase bar but you're looking for uppercase Bar, make sure to use a case-insensitive check (like lowercased().contains("bar")).
• Method Key Paths: For methods, ensure you're referencing the method correctly (no parentheses in the key path, e.g., \Foo.barMethod not \Foo.barMethod()).
• Mirror Limitations: Mirror only inspects public members by default. If your members are private, they won't show up in the mirror results.

内容的提问来源于stack exchange，提问作者Steve