Block-Based Selectors in Swift

BlockBasedSelector.h

//
//  BlockBasedSelector.h
//
//  Created by Charlton Provatas on 11/2/17.
//  Copyright © 2017 CharltonProvatas. All rights reserved.
//

#import <Foundation/Foundation.h>

@interface BlockBasedSelector : NSObject

@end

typedef void (^OBJCBlock)(id _Selector);
typedef void (^OBJCBlockWithSender)(id _Selector, id sender);

void class_addMethodWithBlock(Class class, SEL newSelector, OBJCBlock block);
void class_addMethodWithBlockAndSender(Class class, SEL newSelector, OBJCBlockWithSender block);

BlockBasedSelector.m

//
//  BlockBasedSelector.m
//
//  Created by Charlton Provatas on 11/2/17.
//  Copyright © 2017 CharltonProvatas. All rights reserved.
//

#import "BlockBasedSelector.h"
#import <objc/runtime.h>

@implementation BlockBasedSelector
@end

void class_addMethodWithBlock(Class class, SEL newSelector, OBJCBlock block)
{
    IMP newImplementation = imp_implementationWithBlock(block);
    Method method = class_getInstanceMethod(class, newSelector);
    class_addMethod(class, newSelector, newImplementation,  method_getTypeEncoding(method));
}

void class_addMethodWithBlockAndSender(Class class, SEL newSelector, OBJCBlockWithSender block)
{
    IMP newImplementation = imp_implementationWithBlock(block);
    Method method = class_getInstanceMethod(class, newSelector);
    class_addMethod(class, newSelector, newImplementation,  method_getTypeEncoding(method));
}

BlockBasedSelector.swift

//
//  BlockBasedSelector.swift
//  Parking
//
//  Created by Charlton Provatas on 11/9/17.
//  Copyright © 2017 Charlton Provatas. All rights reserved.
//

import Foundation
// swiftlint:disable identifier_name
func Selector(_ block: @escaping () -> Void) -> Selector {
    let selector = NSSelectorFromString("\(CFAbsoluteTimeGetCurrent())")
    class_addMethodWithBlock(_Selector.self, selector) { _ in block() }
    return selector
}

/// used w/ callback if you need to get sender argument
func Selector(_ block: @escaping (Any?) -> Void) -> Selector {
    let selector = NSSelectorFromString("\(CFAbsoluteTimeGetCurrent())")
    class_addMethodWithBlockAndSender(_Selector.self, selector) { (_, sender) in block(sender) }
    return selector
}

// swiftlint:disable identifier_name
let Selector = _Selector.shared
@objc class _Selector: NSObject {
    static let shared = _Selector()
}

@cprovatas I converted your obj-c code into swift, but sadly I am getting nil from class_getInstanceMethod

func class_addMethodWithBlock(class c: AnyClass, newSelector: Selector, block: @escaping @convention(block) () -> Void) {

    let imp = imp_implementationWithBlock(block)
    guard let method = class_getInstanceMethod(c, newSelector) else {
        fatalError("class_getInstanceMethod")
    }
    class_addMethod(c, newSelector, imp, method_getTypeEncoding(method))
}

func class_addMethodWithBlockAndSender(class c: AnyClass, newSelector: Selector, block: @escaping @convention(block) (Any?) -> Void) {
    let imp = imp_implementationWithBlock(block)
    guard let method = class_getInstanceMethod(c, newSelector) else {
        fatalError("class_getInstanceMethod")
    }
    class_addMethod(c, newSelector, imp, method_getTypeEncoding(method))
}

It leaks memory in swift 5, can you please help me

@cprovatas I converted your obj-c code into swift, but sadly I am getting nil from class_getInstanceMethod

func class_addMethodWithBlock(class c: AnyClass, newSelector: Selector, block: @escaping @convention(block) () -> Void) {

    let imp = imp_implementationWithBlock(block)
    guard let method = class_getInstanceMethod(c, newSelector) else {
        fatalError("class_getInstanceMethod")
    }
    class_addMethod(c, newSelector, imp, method_getTypeEncoding(method))
}

func class_addMethodWithBlockAndSender(class c: AnyClass, newSelector: Selector, block: @escaping @convention(block) (Any?) -> Void) {
    let imp = imp_implementationWithBlock(block)
    guard let method = class_getInstanceMethod(c, newSelector) else {
        fatalError("class_getInstanceMethod")
    }
    class_addMethod(c, newSelector, imp, method_getTypeEncoding(method))
}

Me too return me nil, There is an updated version of the code in swift?

You have to import that class as an objective-c class as there are some issues with how the blocks are bridged into Swift. Just import 'BlockBasedSelector.h' into your bridging header file and everything should work as expected.

There is no license information. Can this be made available for consumption in a commercial application with a good open license? Or is ther any other way to license this for such use?

@lukya yes feel free to use it. this snippet was written independently by myself and isn't the IP of any other entity

Hi maybe you can help me. I take an error when I run method Selector : unrecognized selector sent to instance 0x10dd44ce0'