考虑私有C函数_UICreateScreenUIImage,该函数返回UIImage当前设备屏幕的快照:
_UICreateScreenUIImage
UIImage
OBJC_EXTERN UIImage *_UICreateScreenUIImage(void) NS_RETURNS_RETAINED;
我可以将其放在桥接标头中,然后在Swift中访问它,如下所示:
MyApp-Bridging-Header.h
@import UIKit; UIImage *_UICreateScreenUIImage(void) NS_RETURNS_RETAINED;
MyClass.swift
let image = _UICreateScreenUIImage() print(image) // <UIImage: 0x7fc4ba6081c0>, {375, 667}
有没有一种方法可以_UICreateScreenUIImage在不使用桥接头的情况下在纯Swift中访问?
最初的想法是在上创建扩展UIImage,但是该扩展希望我在扩展中声明函数的主体:
extension UIImage { public func _UICreateScreenUIImage(_: Void) -> UIImage // "Expected '{' in body of function declaration" }
无论如何,这种实现都是有缺陷的,因为_UICreateScreenUIImage上没有方法UIImage。
在纯Swift中是否可以公开和访问此方法?
人们似乎将我的问题与“如何拍摄屏幕截图”混淆了。那不是我要的 我在问如何访问UIImage *_UICreateScreenUIImage(void);Swift中的方法。它可以是任何私有方法,例如+(UIImage *)_deviceSpecificImageNamed:(NSString *)name inBundle:(NSBundle *)bundle;或+(UIImage *)_pu_PhotosUIImageNamed:(NSString *)name;。
UIImage *_UICreateScreenUIImage(void);
+(UIImage *)_deviceSpecificImageNamed:(NSString *)name inBundle:(NSBundle *)bundle;
+(UIImage *)_pu_PhotosUIImageNamed:(NSString *)name;
它比您预期的容易得多:
@asmname("_UICreateScreenUIImage") func _UICreateScreenUIImage() -> UIImage // That's it – go ahead and call it: _UICreateScreenUIImage()
碰巧的是,@asmname实际上 只是 在2.3版本中将更改为@_silgen_name,因此准备相应地进行调整:
@asmname
@_silgen_name
@_silgen_name("_UICreateScreenUIImage") func _UICreateScreenUIImage() -> UIImage
据我所知,@_silgen_name没有提供Objective-C方法的解析。为此,有更强大的Objective-C运行时API:
let invokeImageNamed: (String, NSTimeInterval) -> UIImage? = { // The Objective-C selector for the method. let selector: Selector = "animatedImageNamed:duration:" guard case let method = class_getClassMethod(UIImage.self, selector) where method != nil else { fatalError("Failed to look up \(selector)") } // Recreation of the method's implementation function. typealias Prototype = @convention(c) (AnyClass, Selector, NSString, NSTimeInterval) -> UIImage? let opaqueIMP = method_getImplementation(method) let function = unsafeBitCast(opaqueIMP, Prototype.self) // Capture the implemenation data in a closure that can be invoked at any time. return { name, interval in function(UIImage.self, selector, name, interval) } }() extension UIImage { // Convenience method for calling the closure from the class. class func imageNamed(name: String, interval: NSTimeInterval) -> UIImage? { return invokeImageNamed(name, interval) } } UIImage.imageNamed("test", interval: 0)
就处理而言NS_RETURNS_RETAINED,这不会为您生成。相反,您可以使用的返回类型Unmanaged,并将其包装在函数中以方便使用:
NS_RETURNS_RETAINED
Unmanaged
@_silgen_name("_UICreateScreenUIImage") func _UICreateScreenUIImage() -> Unmanaged<UIImage> func UICreateScreenUIImage() -> UIImage { return _UICreateScreenUIImage().takeRetainedValue() }