List all classes that subscribe a protocol

listClasses.swift

// Many thanks to Code Different: http://stackoverflow.com/a/42749141/3440266
import Foundation

struct ClassInfo : CustomStringConvertible, Equatable {
    let classObject: AnyClass
    let classNameFull: String
    let className: String
    
    init?(_ classObject: AnyClass?) {
        guard classObject != nil else { return nil }
        
        self.classObject = classObject!
        
        let cName = class_getName(classObject)!
        self.classNameFull = String(cString: cName)
        self.className = self.classNameFull.components(separatedBy: ".").last!
    }
    
    var superclassInfo: ClassInfo? {
        let superclassObject: AnyClass? = class_getSuperclass(self.classObject)
        return ClassInfo(superclassObject)
    }
    
    var description: String {
        return self.classNameFull
    }
    
    static func ==(lhs: ClassInfo, rhs: ClassInfo) -> Bool {
        return lhs.classNameFull == rhs.classNameFull
    }
}

////
// List classes that are subclasses
func subclasses(of classMother: AnyClass) -> [ClassInfo] {
    let motherClassInfo = ClassInfo(classMother.self)!
    var subclassesList = [ClassInfo]()
    
    var count = UInt32(0)
    let classList = objc_copyClassList(&count)!
    
    for i in 0..<Int(count) {
        if let classInfo = ClassInfo(classList[i]),
            let superclassInfo = classInfo.superclassInfo,
            superclassInfo == motherClassInfo
        {
            subclassesList.append(classInfo)
        }
    }
    
    return subclassesList
}

// Example
class Mother { }
class Brother: Mother { }
class Sister: Mother { }
class Cousin { }

let listSubclasses = subclasses(of: Mother.self)
print(listSubclasses)

////
// List classes that subscribers a protocol
func subscribers<T>(of: T.Type) -> [ClassInfo] {
    var subscribersList = [ClassInfo]()
    
    var count = UInt32(0)
    let classList = objc_copyClassList(&count)!
    
    for i in 0..<Int(count) {
        if let classInfo = ClassInfo(classList[i]) {
            
            // skip native Swift and Foundation classes, to do not crash
            if classInfo.classNameFull.components(separatedBy: ".").count == 1 {
                continue
            }
            
            //
            if classInfo.classObject is T {
                subscribersList.append(classInfo)
            }
        }
    }
    
    return subscribersList
}

// Example
protocol Proto { }
protocol Proto2 { }
class Foo: Proto { }
class Bar: Proto, Proto2 { }
class Baz: Proto2 { }
class Qux { }

let listProto = subscribers(of: Proto.Type.self )
print(listProto)