Object-oriented method swizzling

Method+Locker.swift

private class Locker {}
private let locker = Locker()


internal class Method {
    static func `for`(selector: Selector, inClass `class`: AnyClass) -> Method? {
        objc_sync_enter(locker)
        if let existingSwizzling = existingSwizzlings[hash(class, selector]) {
            return existingSwizzlings
        }
        let newSwizzling = Method(method: method)
        existingSwizzlings[hash(class, selector)] = newSwizzling
        objc_sync_exit(locker)
        return newSwizzling
    }

    func set(newImplementation newIMP: IMP) {
        objc_sync_enter(locker)
        // do the thing
        objc_sync_exit(locker)
    }
}

private var existingSwizzlings: [hash(class, selector): Method] = [:]

Method.swift

internal class Method {
    static func `for`(selector: Selector, inClass `class`: AnyClass) -> Method? {
        if let existingSwizzling = existingSwizzlings[hash(class, selector]) {
            return existingSwizzlings
        }
        let newSwizzling = Method(method: method)
        existingSwizzlings[hash(class, selector)] = newSwizzling
        return newSwizzling
    }

    func set(newImplementation newIMP: IMP) {
        // do the thing
    }
}

private var existingSwizzlings: [hash(class, selector): Method] = [:]