无法识别的选择器调用“_setApplicationIsOpaque:”

Question

我正在尝试访问 iOS 私有函数 _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 Whosebug 问题中找到了这种访问私有 iOS API 的方式 this file GitHub.

问题是运行我收到错误的应用程序

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

我找到了 UIApplication in this GitHub repository 的 iOS 私有 API 的 header。

Answer 1

- (void)_setApplicationIsOpaque:(BOOL)arg1;

是一个实例方法（属于 UIApplication），如初始连字符 -。实例方法被发送到一个实例 class，而不是 class 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 运行时编程指南”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”是实例消息被发送，在你的例子中是 UIApplication 实例。（对于 class 方法 它将是 class 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)
    }
}

注意这里不需要_silgen_name声明。

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

将Swift函数绑定到全局符号“_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:"

无法识别的选择器调用“_setApplicationIsOpaque:”

Unrecognised selector invoking "_setApplicationIsOpaque:"

objective-c

iphone-privateapi

ios

swift