高效重构Swift代码，减少冗余

Question

在下面的代码中，A键被重新映射为B键，反之亦然。通过SwiftUI拨动开关激活重新映射。

---

在这里给出的示例中，相同的代码块用于三个不同的函数。

此外，遍历函数调用的循环也在这三个函数中使用。

一天多来，我一直在努力简化这段代码，使其不那么冗余。如有任何帮助，我将不胜感激。

---

let aKey: UInt64 = 0x700000004
let bKey: UInt64 = 0x700000005
func isKeyboardServiceClientForUsagePage(_ serviceClient: IOHIDServiceClient, _ usagePage: UInt32, _ usage: UInt32) -> Bool {
return IOHIDServiceClientConformsTo(serviceClient, usagePage, usage) == 1
}
func updateKeyboardKeyMapping(_ keyMap: [[String: UInt64]]) {
let eventSystemClient = IOHIDEventSystemClientCreateSimpleClient(kCFAllocatorDefault)
guard let serviceClients = IOHIDEventSystemClientCopyServices(eventSystemClient) as? [IOHIDServiceClient] else {
return
}
for serviceClient in serviceClients {
let usagePage = UInt32(kHIDPage_GenericDesktop)
let usage = UInt32(kHIDUsage_GD_Keyboard)
if isKeyboardServiceClientForUsagePage(serviceClient, usagePage, usage) {
IOHIDServiceClientSetProperty(serviceClient, kIOHIDUserKeyUsageMapKey as CFString, keyMap as CFArray)
}
}
}
func areKeysMappedOnAnyServiceClient() -> Bool {
let eventSystemClient = IOHIDEventSystemClientCreateSimpleClient(kCFAllocatorDefault)
guard let serviceClients = IOHIDEventSystemClientCopyServices(eventSystemClient) as? [IOHIDServiceClient] else {
return false
}
for serviceClient in serviceClients {
let usagePage = UInt32(kHIDPage_GenericDesktop)
let usage = UInt32(kHIDUsage_GD_Keyboard)
if isKeyboardServiceClientForUsagePage(serviceClient, usagePage, usage) {
guard let keyMapping = IOHIDServiceClientCopyProperty(serviceClient, kIOHIDUserKeyUsageMapKey as CFString) as? [[String: UInt64]] else {
return false
}
if keyMapping.contains(where: { $0[kIOHIDKeyboardModifierMappingSrcKey] == aKey && $0[kIOHIDKeyboardModifierMappingDstKey] == bKey }) &&
keyMapping.contains(where: { $0[kIOHIDKeyboardModifierMappingSrcKey] == bKey && $0[kIOHIDKeyboardModifierMappingDstKey] == aKey })
{
return true
}
}
}
return false
}
func remapABBA() {
let keyMap: [[String: UInt64]] = [
[
kIOHIDKeyboardModifierMappingSrcKey: aKey,
kIOHIDKeyboardModifierMappingDstKey: bKey,
],
[
kIOHIDKeyboardModifierMappingSrcKey: bKey,
kIOHIDKeyboardModifierMappingDstKey: aKey,
],
]
updateKeyboardKeyMapping(keyMap)
}
func resetKeyMapping() {
updateKeyboardKeyMapping([])
}

---

如果你想尝试这个应用程序，这里是SwiftUI部分:

import SwiftUI
struct ContentView: View {
@State private var remapKeys = areKeysMappedOnAnyServiceClient()
var body: some View {
HStack {
Spacer()
Toggle(isOn: $remapKeys, label: { Text("Remap A → B and B → A.") })
.toggleStyle(SwitchToggleStyle())
.onChange(of: remapKeys, perform: toggleKeyboardRemapping)
Spacer()
}
}
}
private func toggleKeyboardRemapping(_ remapKeys: Bool) {
if remapKeys {
remapABBA()
} else {
resetKeyMapping()
}
}

Answer 1

OK…回答这个问题需要一些时间。

看来你缺少一个地方来存放东西。这就是为什么你必须一遍又一遍地使用相同的代码块。我们可以用视图模型来解决这个问题…

在这里，我将隐藏视图正在发生的逻辑，只暴露视图需要访问的内容，以便显示自己。

// we make it observable so the view can subscribe to it.
class KeyMappingViewModel: ObservableObject {
private let aKey: UInt64 = 0x700000004
private let bKey: UInt64 = 0x700000005
private let srcKey = kIOHIDKeyboardModifierMappingSrcKey
private let dstKey = kIOHIDKeyboardModifierMappingDstKey
private var keyMap: [[String: UInt64]] {
[
[
srcKey: aKey,
dstKey: bKey,
],
[
srcKey: bKey,
dstKey: aKey,
],
]
}
// A more concise way to get hold of the client ref
private var client: IOHIDEventSystemClientRef {
IOHIDEventSystemClientCreateSimpleClient(kCFAllocatorDefault)
}
// Making this published means the view can use it as state in the Toggle
@Published var toggleState: Bool {
didSet {
if toggleState {
client.updateKeyMapping(keyMap)
} else {
client.updateKeyMapping([])
}
}
}
init() {
// set the initial value by asking the client if it has any keys mapped
toggleState = client.areKeysMappedOnAnyServiceClient(aKey: aKey, bKey: bKey)
}
}

我将扩展IOHIDServiceClient和IOHIDEventSystemClientRef来封装你的逻辑…

extension IOHIDEventSystemClientRef {
private var srcKey: String { kIOHIDKeyboardModifierMappingSrcKey }
private var dstKey: String { kIOHIDKeyboardModifierMappingDstKey }
// Make this an optional var on the client ref itself.
private var serviceClients: [IOHIDServiceClient]? {
IOHIDEventSystemClientCopyServices(self) as? [IOHIDServiceClient]
}
func areKeysMappedOnAnyServiceClient(aKey: UInt64, bKey: UInt64) -> Bool {
// Nice Swift 5.7 syntax with the optional var
guard let serviceClients else {
return false
}
// I made this more concise with a filter and map.
// Also, using the extension we can make use of keyPaths to get the values.
return serviceClients.filter(.isForGDKeyboard)
.compactMap(.keyMapping)
.map { keyMapping in
keyMapping.contains(where: { $0[srcKey] == aKey && $0[dstKey] == bKey }) &&
keyMapping.contains(where: { $0[srcKey] == bKey && $0[dstKey] == aKey })
}
.contains(true)
}
func updateKeyMapping(_ keyMap: [[String: UInt64]]) {
// serviceClients is optional so we can just ? it.
// if it's nil, nothing after the ? happens.
serviceClients?.filter(.isForGDKeyboard)
.forEach {
IOHIDServiceClientSetProperty($0, kIOHIDUserKeyUsageMapKey as CFString, keyMap as CFArray)
}
}
}
extension IOHIDServiceClient {
var isForGDKeyboard: Bool {
let usagePage = UInt32(kHIDPage_GenericDesktop)
let usage = UInt32(kHIDUsage_GD_Keyboard)
return IOHIDServiceClientConformsTo(self, usagePage, usage) == 1
}
var keyMapping: [[String: UInt64]]? {
IOHIDServiceClientCopyProperty(self, kIOHIDUserKeyUsageMapKey as CFString) as? [[String: UInt64]]
}
}

做所有这些意味着你的视图看起来像这样…

import SwiftUI
struct ContentView: View {
@ObservedObject var viewModel: KeyMappingViewModel = .init()
var body: some View {
HStack {
Spacer()
Toggle(isOn: $viewModel.toggleState) {
Text("Remap A → B and B → A.")
}
.toggleStyle(SwitchToggleStyle())
Spacer()
}
}
}

这包含了你所有的逻辑和TBH已经不太糟糕了。

我的主要改动是将自由函数和变量添加到它们各自的类型中。

因此，update和areKeysMapped...函数现在属于IOHIDEventSystemClientRef类型。

isForGDKeyboard和keyMapping变量现在属于IOHIDServiceClient类型。

这样做删除了大量重复的代码，因为您不再需要连续调用自由函数。这也意味着我们解锁了一些非常快速的keyPath用法，这有助于使一些逻辑更简洁。

然后我们创建了一个视图模型。这允许我们将视图的所有移动部分保持在一个地方。它有一个很容易联系到客户的地方。这也意味着我们可以通过将视图模型设为私有来隐藏很多东西。

这意味着视图只能做一件事。这是使用绑定到toggleState。其他一切都是闭门造车。