// use closure
let command = ReactiveCommand<InputType, OutputType>(execute: (InputType) -> OutputType, canExecute: Observable<Bool>)

// transform observable
let loadMoreCommand = ReactiveCommand<Int, Post>(execute: postService.load)

// combined command
// The Input Type must be the same.
// OutputType does not matter.
let removeA = ReactiveCommand<Void, Void>(execute...)
let removeB = ReactiveCommand<Void, Void>(execute...)
let removeC = ReactiveCommand<Void, Void>(execute...)
let removeAllCommand = ReactiveCommand.combined(with: removeA.asCommandExecuter(), removeB.asCommandExecuter(), removeC.asCommandExecuter())

let command = ReactiveCommand<Input, Output>.init(...)
command.subscribe(onNext: { Output in
    // something
})

let saveCommand = ReactiveCommand<Void, Output).init(...)
var saveButton: UIButton
saveButton.bind(to: saveCommand.asCommandExecuter()).disposed(by: disposeBag)

// Binding with TextField like passcode
let passCommand = ReactiveCommand<String, Void>(execute: { (code) in
    // code
})
let combinedEexecutor = passCommand.combined(with: textField.rx.text.orEmpty.asObservable())
doneButton.bind(to: combinedEexecutor).disposed(by: disposeBag)