Programming language: Swift
License: Apache License 2.0
Tags: Utility    
Latest version: v0.1.0

Lumos alternatives and similar libraries

Based on the "Utility" category.
Alternatively, view Lumos alternatives based on common mentions on social networks and blogs.

Do you think we are missing an alternative of Lumos or a related project?

Add another 'Utility' Library


A light wrapper around Objective-C Runtime.

What exactly is lumos?

lumos as mentioned is a light wrapper around objective-c runtime functions to allow an easier access to the runtime. It makes operations such as swizzling and hooking very simple in Swift.

For example, say you wish to run a block of code whenever a ViewController's viewDidLoad method is called

With lumos, you can do the following:

// In AppDelegate (or any conveinient place)..

let method = Lumos.for(ViewController.self).getInstanceMethod(selector: #selector(ViewController.viewDidLoad))

method?.prepend {
    // This block will be run every time a viewDidLoad is called
    print("View Controller loaded")

Similarily you can append a block to a method which will be called right before the method returns. You can even use replace to replace the method's implementation with the block you pass in as a parameter.

If you wanted more flexibility, you could swizzle the viewDidLoad method using the following lines:

@objc func myMethod() {
    // Do anything here

let myMethod = self.lumos.getInstanceMethod(selector: #selector(myMethod))

method?.swapImplementation(with: myMethod)

Do you feel the superpower yet? Maybe you wish to list all the classes registered at runtime:


Fun Fact: There are almost 12,000 classes registered at runtime Try Lumos.getAllClasses().count

You could get the class hierarchy of any class just with:

myObject.lumos.getClassHierarcy()   // For UIView: [UIView, UIResponder, NSObject]

Fun Fact: Some classes such as URLSessionTask are actually dummy classes which are replaced with underlying classes such as __NSCFLocalSessionTask during runtime.

With lumos, you can iterate through variables, functions, protocols etc and meddle with them at runtime. Have fun exploring!


Just incantate .lumos on any instance of a NSObject subclass or use Lumos.for(object) for where object is of type AnyClass, AnyObject, Protocol, Ivar, objc_property_t or objc_property_attribute_t.

P.s The code itself is the documentation for now. There are many more methods that lumos offers which are not discussed in this document. Cheers :)

Why lumos?

The Objective-C Runtime provides many powerful methods to manipulate objects, classes and methods at runtime. Although disasterous when misused, these methods provide a great way to peek into the runtime and meddle with it.

However, the methods are not exactly easy to use sometimes. For example the following method is used to obtain a list of all classes registered at runtime:

func objc_getClassList(_ buffer: AutoreleasingUnsafeMutablePointer<AnyClass>?, _ bufferCount: Int32) -> Int32

Often, a lot of dirty work needs to be done before one gets the list out. Here is how I would do it:

static func getClassList() -> [AnyClass] {
    let expectedClassCount = objc_getClassList(nil, 0)
    let allClasses = UnsafeMutablePointer<AnyClass?>.allocate(capacity: Int(expectedClassCount))

    let autoreleasingAllClasses = AutoreleasingUnsafeMutablePointer<AnyClass>(allClasses)
    let actualClassCount: Int32 = objc_getClassList(autoreleasingAllClasses, expectedClassCount)

    var classes = [AnyClass]()
    for i in 0 ..< actualClassCount {
        if let currentClass: AnyClass = allClasses[Int(i)] {

    return classes

Now all you would need to do to obtain the list of classes would be to invoke this method. Maybe you wish to get a list of classes that conform to a certain protocol:

static func classesImplementingProtocol(_ requiredProtocol: Protocol) -> [AnyClass] {
    return Lumos.getClassList().filter { class_conformsToProtocol($0, requiredProtocol) }

Perhaps you wish to swizzle method implementations at runtime:

static func swizzle(originalClass: AnyClass, originalSelector: Selector, swizzledClass: AnyClass, swizzledSelector: Selector) {
    guard let originalMethod = class_getInstanceMethod(originalClass, originalSelector),
    let swizzledMethod = class_getInstanceMethod(swizzledClass, swizzledSelector) else {

    let didAddMethod = class_addMethod(originalClass, originalSelector, method_getImplementation(swizzledMethod), method_getTypeEncoding(swizzledMethod))

    if didAddMethod {
        class_replaceMethod(originalClass, swizzledSelector, method_getImplementation(originalMethod), method_getTypeEncoding(originalMethod))
    } else {
        method_exchangeImplementations(originalMethod, swizzledMethod);

You can now use:

Lumos.swizzle(originalClass: URLSessionTask,
              originalSelector: #selector(URLSessionTask.resume),
              swizzledClass: SwizzledSessionTask,
              swizzledSelector: #selector(SwizzledSessionTask.resume))

P.S you might want to use dispatch_once with the method above to above swizzling more than once across multiple threads.



CocoaPods is a dependency manager for Cocoa projects. You can install it with the following command:

$ gem install cocoapods

To integrate lumos into your Xcode project using CocoaPods, specify it in your Podfile:

source 'https://github.com/CocoaPods/Specs.git'
platform :ios, '10.0'

target '<Your Target Name>' do
    pod 'Lumos'

Then, run the following command:

$ pod install


Lumos is released under the Apache-2.0. See LICENSE for details.

*Note that all licence references and agreements mentioned in the Lumos README section above are relevant to that project's source code only.