Swizzle

Swizzle.md

Swizzle 1 works (somehow)

The login() function is in the extension The fakeLogin() function is in the main class

Swizzle 2 does not work as expected

The login() function is in the main class The fakeLogin() function is in the extension

Swizzle 3 does work as expected

The dynamic login() function is in the main class The fakeLogin() function is in the extension

Swizzle.swift

import Cocoa
import Foundation

// MARK: Swizzle
func swizzle(class kClass: AnyClass, oldSelector: Selector, with newSelector: Selector) {
    guard let oldImplementation = class_getInstanceMethod(kClass, oldSelector) else {
        print("Could not extract original implementation")
        return
    }
    
    guard let newImplementation = class_getInstanceMethod(kClass, newSelector) else {
        print("Could not find new implementation")
        return
    }
    
    method_exchangeImplementations(oldImplementation, newImplementation)
}

// MARK: Test class 1
class testClass1 {
    @objc func fakeLogin() -> Bool {
        return true
    }
}
extension testClass1 {
    @objc func login() -> Bool {
        return false
    }
}

// MARK: Test class 2
class testClass2 {
    @objc func login() -> Bool {
        return false
    }
}
extension testClass2 {
    @objc func fakeLogin() -> Bool {
        return true
    }
}

// MARK: Test class 3
class testClass3 {
    @objc dynamic func login() -> Bool {
        return false
    }
}
extension testClass3 {
    @objc func fakeLogin() -> Bool {
        return true
    }
}

/**
* Test case 1.
* .
* The original login is in a extension.
* .
* Expected behaviour: [1] Welcome
* What happens: [1] Welcome
*/
// MARK: Shizzle 1
swizzle(
    class: testClass1.self,
    oldSelector: #selector(testClass1.login),
    with: #selector(testClass1.fakeLogin)
)

// MARK: Test 1
if (testClass1().login()) {
    print("[1] Welcome")
} else {
    print("[1] Bad login")
}

/**
* Test case 2.
* .
* The fake login is in a extension.
* .
* Expected behaviour: [2] Welcome
* What happens: [2] Bad login
*/
// MARK: Shizzle 2
swizzle(
    class: testClass2.self,
    oldSelector: #selector(testClass2.login),
    with: #selector(testClass2.fakeLogin)
)

// MARK: Test 2
if (testClass2().login()) {
    print("[2] Welcome")
} else {
    print("[2] Bad login")
}

/**
* Test case 3.
* .
* The login is dynamic.
* .
* Expected behaviour: [3] Welcome
* What happens: [3] Welcome
*/
// MARK: Shizzle 3
swizzle(
    class: testClass3.self,
    oldSelector: #selector(testClass3.login),
    with: #selector(testClass3.fakeLogin)
)

// MARK: Test 3
if (testClass3().login()) {
    print("[3] Welcome")
} else {
    print("[3] Bad login")
}