無法識別的選擇器調用「_setApplicationIsOpaque：」

Question

我想訪問iOS專用功能_setApplicationIsOpaque:（僅供個人使用和測試）。

我已經實現了這個代碼：

@_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) 
    } 
} 

我發現這種方式來訪問私有的iOS API在下面的StackOverflow問題Access Private UIKit Function Without Using Bridging Header 和this file在GitHub上。

的問題是，在運行應用程序，我得到的錯誤

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

我發現的UIApplication in this GitHub repository iOS的私有的API的報頭。

Answer 1

- (void)_setApplicationIsOpaque:(BOOL)arg1; 

是實例方法（的UIApplication），由 初始連字符-所示。實例方法被髮送到類的實例 ，而不是類本身。

Objective-C的方法是C函數與兩個隱藏參數， 「Objective-C運行編程指南」 中比較 Messaging ：

It also passes the procedure two hidden arguments:

• The receiving object
• The selector for the method

對於實例方法， 「接收對象」 是實例到 哪個消息被髮送，在你的情況下是UIApplication實例。 （對於類方法它將是類對象）。

因此雨燕擴展方法setApplicationIsOpaque 必須通過self於封閉，而且必須爲 傳遞的第一個參數的實現方法：即_silgen_name聲明不

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) 
    } 
} 

---

注需要在這裏。

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

結合雨燕功能全局符號「_setApplicationIsOpaque」， 不存在。如果你想添加一個調用該函數

_setApplicationIsOpaque(true) 

然後構建應用程序將失敗，並鏈接錯誤：

 
Undefined symbols for architecture x86_64: "__setApplicationIsOpaque:"