filtersample.swift

import UIKit
import RxSwift
import RxBlocking
import RxCocoa

class ViewController: UIViewController {

    @IBOutlet weak var textField: UITextField!
    @IBOutlet weak var label: UILabel!
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        textField.rx_text.filter { text -> Bool in
            return text.characters.count >= 3
        }.subscribeNext { [unowned self] text in
            self.label.text = text
        }
    }
}