func printIvarsForClass(cls: AnyClass) {
        var ivarCount: UInt32 = 0
        let ivarList = class_copyIvarList(cls, &ivarCount)
        if let ivarList = ivarList, ivarCount > 0 {
            enumerateCArray(array: ivarList, count: ivarCount) { i, v in
                let name = ivar(v: v) ?? "unknown"
                print("#\(i): \(name)")
            }

            free(ivarList)
        }
    }
    func enumerateCArray<T>(array: UnsafePointer<T>, count: UInt32, f: (UInt32, T) -> Void) {
        var ptr = array
        for i in 0..<count {
            f(i, ptr.pointee)
            ptr = ptr.successor()
        }
    }
    func ivar(v: Ivar) -> String? {
        guard let p = ivar_getName(v) else { return nil }
        return String(cString: p)
    }
    func printIvarsForClassNamed(classname: String) {
        // NSClassFromString() is declared to return AnyClass!, but should be AnyClass?
        let maybeClass: AnyClass? = NSClassFromString(classname)
        if let cls: AnyClass = maybeClass {
            printIvarsForClass(cls: cls)
        } else {
            print("\(classname): no such class")
        }
    }

    func printMethodNamesForClass(cls: AnyClass) {
        var methodCount: UInt32 = 0
        let methodList = class_copyMethodList(cls, &methodCount)
        if let methodList = methodList, methodCount > 0 {
            enumerateCArray(array: methodList, count: methodCount) { i, m in
                let name = methodName(m: m) ?? "unknown"
                print("#\(i): \(name)")
            }

            free(methodList)
        }
    }

    func methodName(m: Method) -> String? {
        let sel = method_getName(m)
        let nameCString = sel_getName(sel)
        return String(cString: nameCString)
    }

    func printMethodNamesForClassNamed(classname: String) {
        // NSClassFromString() is declared to return AnyClass!, but should be AnyClass?
        let maybeClass: AnyClass? = NSClassFromString(classname)
        if let cls: AnyClass = maybeClass {
            printMethodNamesForClass(cls: cls)
        } else {
            print("\(classname): no such class")
        }
    }