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Created September 7, 2020 14:42
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import Foundation
// MARK: - Protocols
@objc protocol NSMethodSignaturePrivate {
static func signature(objCTypes: UnsafePointer<CChar>) -> NSMethodSignaturePrivate?
var numberOfArguments: Int { get }
@objc(getArgumentTypeAtIndex:) func getArgumentType(at index: Int) -> UnsafePointer<CChar>
var frameLength: Int { get }
var isOneway: ObjCBool { get }
var methodReturnType: UnsafePointer<CChar> { get }
var methodReturnLength: Int { get }
@objc protocol NSInvocationPrivate {
static func invocation(methodSignature: NSMethodSignaturePrivate) -> NSInvocationPrivate
var methodSignature: NSMethodSignaturePrivate { get }
func retainArguments()
var argumentsRetained: ObjCBool { get }
var target: AnyObject { get set }
var selector: Selector { get set }
func getReturnValue(_ location: UnsafeMutableRawPointer)
func setReturnValue(_ location: UnsafeRawPointer)
@objc(getArgument:atIndex:) func getArgument(_ location: UnsafeMutableRawPointer, at index: Int)
@objc(setArgument:atIndex:) func setArgument(_ location: UnsafeRawPointer, at index: Int)
func invoke()
func invoke(target: AnyObject)
@objc protocol NSObjectPrivate {
@objc(methodSignatureForSelector:) func methodSignature(for selector: Selector) -> NSMethodSignaturePrivate?
func forwardInvocation(_ invocation: NSInvocationPrivate)
// MARK: - Import class helper
func importClass<ProtocolType>(_ className: String) -> ProtocolType {
let typeNameSuffix = ".Type"
let protocolTypeName = String(reflecting: ProtocolType.self)
guard protocolTypeName.hasSuffix(typeNameSuffix) else {
preconditionFailure("Type `\(protocolTypeName)` is not a protocol type.")
let protocolName = protocolTypeName.dropLast(typeNameSuffix.count)
guard let `protocol` = protocolName.withCString(objc_getProtocol) else {
preconditionFailure("Type `\(protocolName)` is not an objc protocol.")
guard let `class` = className.withCString(objc_getClass) as? AnyClass else {
preconditionFailure("Class `\(className)` not found.")
if !class_addProtocol(`class`, `protocol`) {
assertionFailure("Failed to attach protocol `\(protocolName)` to class `\(className)`.")
guard let result = `class` as? ProtocolType else {
fatalError("Failed to cast class `\(className)` to protocol `\(protocolName)`.")
return result
// MARK: - Import classes
let NSMethodSignatureClass = importClass("NSMethodSignature") as NSMethodSignaturePrivate.Type
let NSInvocationClass = importClass("NSInvocation") as NSInvocationPrivate.Type
let NSObjectClass = importClass("NSObject") as NSObjectPrivate.Type
// MARK: - Try out the NSInvocation
let object = NSDate()
let objectPrivate = object as! NSObjectPrivate
let selector = Selector("description")
let signature = objectPrivate.methodSignature(for: selector)!
let invocation = NSInvocationClass.invocation(methodSignature: signature)
invocation.selector = selector
invocation.invoke(target: object)
var unmanagedResult: Unmanaged<NSString>? = nil
let result = unmanagedResult?.takeRetainedValue()
print(result ?? "<nil>")
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