Swift isa 指针重新映射或其他支持的方法调配

Swift isa 指针重新映射或其他支持的方法调配

swift
class Animal {
    func makeSound() {
        print("Animal makes a sound")
    }
}
class Cat: Animal {
    override func makeSound() {
        print("Meow!")
    }
}
class Dog: Animal {
    override func makeSound() {
        print("Woof!")
    }
}
let animal = Animal()
animal.makeSound() // 输出：Animal makes a sound
let cat = Cat()
cat.makeSound() // 输出：Meow!
let dog = Dog()
dog.makeSound() // 输出：Woof!
let animalAsCat = unsafeBitCast(animal, to: Cat.self)
animalAsCat.makeSound() // 输出：Meow!

swift
class Math {
    func add(a: Int, b: Int) -> Int {
        return a + b
    }
    
    func subtract(a: Int, b: Int) -> Int {
        return a - b
    }
}
let math = Math()
let addFunction = unsafeBitCast(math.add, to: (@convention(c) (AnyObject, Selector, Int, Int) -> Int).self)
let subtractFunction = unsafeBitCast(math.subtract, to: (@convention(c) (AnyObject, Selector, Int, Int) -> Int).self)
let result1 = addFunction(math, #selector(Math.add(a:b:)), 3, 2)
print(result1) // 输出：5
let result2 = subtractFunction(math, #selector(Math.subtract(a:b:)), 3, 2)
print(result2) // 输出：1