ios - 无法识别的选择器调用 "_setApplicationIsOpaque:"

Question

我正在尝试访问 iOS 私有(private)函数 _setApplicationIsOpaque:(仅供个人使用和测试)。

我已经实现了这段代码:

@_silgen_name("_setApplicationIsOpaque:") func _setApplicationIsOpaque(_ arg1: Bool)

let invokeSetApplicationIsOpaque: (Bool) -> Void = {
    // The Objective-C selector for the method.
    let selector: Selector = Selector(("_setApplicationIsOpaque:"))
    guard case let method = class_getInstanceMethod(UIApplication.self, selector), method != nil else {
        fatalError("Failed to look up \(selector)")
    }

    // Recreation of the method's implementation function.
    typealias Prototype = @convention(c) (AnyClass, Selector, Bool) -> Void
    let opaqueIMP = method_getImplementation(method)
    let function = unsafeBitCast(opaqueIMP, to: Prototype.self)

    // Capture the implemenation data in a closure that can be invoked at any time.
    return{ arg1 in function(UIApplication.self, selector, arg1)}
}()

extension UIApplication {
    func setApplicationIsOpaque(_ isOpaque: Bool) {
        return invokeSetApplicationIsOpaque(isOpaque)
    }
}

我在以下 StackOverflow 问题 Access Private UIKit Function Without Using Bridging Header 中找到了这种访问私有(private) iOS API 的方法在this file在 GitHub 上。

问题是运行应用程序时出现错误

[UIApplication _setBackgroundStyle:]: unrecognized selector sent to class 0x10437f348

我找到了 UIApplication 的 iOS 私有(private) API 的 header in this GitHub repository .

Answer 1

- (void)_setApplicationIsOpaque:(BOOL)arg1;

是实例方法(属于UIApplication)，如初始连字符 -。实例方法被发送到一个实例类，而不是类本身。

Objective-C 方法是带有两个隐藏参数的 C 函数，比较 Messaging在《Objective-C Runtime Programming Guide》中:

It also passes the procedure two hidden arguments:

• The receiving object
• The selector for the method

对于实例方法，“接收对象”是实例发送消息的对象，在您的例子中是 UIApplication 实例。(对于类方法，它将是类对象)。

因此 Swift 扩展方法 setApplicationIsOpaque必须将 self 传递给闭包，并且必须将其传递为实现方法的第一个参数:

let invokeSetApplicationIsOpaque: (UIApplication, Bool) -> Void = {
    // The Objective-C selector for the method.
    let selector = Selector(("_setApplicationIsOpaque:"))
    guard case let method = class_getInstanceMethod(UIApplication.self, selector), method != nil else {
        fatalError("Failed to look up \(selector)")
    }
    
    // Recreation of the method's implementation function.
    typealias Prototype = @convention(c) (UIApplication, Selector, Bool) -> Void
    let opaqueIMP = method_getImplementation(method)
    let function = unsafeBitCast(opaqueIMP, to: Prototype.self)
    
    // Capture the implemenation data in a closure that can be invoked at any time.
    return { (appl, arg1) in function(appl, selector, arg1)}
}()

extension UIApplication {
    func setApplicationIsOpaque(_ isOpaque: Bool) {
        return invokeSetApplicationIsOpaque(self, isOpaque)
    }
}

---

请注意，此处不需要 _silgen_name 声明。

@_silgen_name("_setApplicationIsOpaque:") func _setApplicationIsOpaque(_ arg1: Bool)

将 Swift 函数绑定(bind)到全局符号“_setApplicationIsOpaque”，这是不存在的。如果您要添加对该函数的调用

_setApplicationIsOpaque(true)

然后构建应用程序将失败并出现链接器错误:

Undefined symbols for architecture x86_64:  "__setApplicationIsOpaque:"