UIPickerViewDefaultValue(MultiComponents).swift

//
//  ViewController.swift
//  SwiftPicker
//
//  Created by 默司 on 2016/8/8.
//  Copyright © 2016年 默司. All rights reserved.
//

import UIKit

class ViewController: UIViewController, UIPickerViewDelegate, UIPickerViewDataSource {
    
    @IBOutlet weak var textField: UITextField!
    
    let picker = UIPickerView()
    let options = ["First", "Second", "Third"]
    let optionsChild = [["A", "B", "C", "D"], ["D", "E", "F"], ["X", "Y", "Z", "BlahBlah"]]
    
    var text = ""
    var textChild = ""
    
    override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view, typically from a nib.
        
        textField.inputView = picker
        
        picker.delegate = self
        picker.dataSource = self
        
        picker.selectRow(0, inComponent: 0, animated: false)
        picker.selectRow(0, inComponent: 1, animated: false)
        
        selectAndTrigger(row: 0, component: 0)
        selectAndTrigger(row: 0, component: 1)
    }
    
    func pickerView(pickerView: UIPickerView, numberOfRowsInComponent component: Int) -> Int {
        if component == 0 {
            return options.count
        } else {
            return optionsChild[pickerView.selectedRowInComponent(0)].count
        }
    }
    
    func numberOfComponentsInPickerView(pickerView: UIPickerView) -> Int {
        return 2
    }
    
    func pickerView(pickerView: UIPickerView, titleForRow row: Int, forComponent component: Int) -> String? {
        if component == 0 {
            return options[row]
        } else {
            return optionsChild[pickerView.selectedRowInComponent(0)][row]
        }
        
    }
    
    func pickerView(pickerView: UIPickerView, didSelectRow row: Int, inComponent component: Int) {
        
        if component == 0 {
            text = options[row]
            pickerView.reloadComponent(1)
            pickerView.selectRow(0, inComponent: 1, animated: true)
            self.pickerView(pickerView, didSelectRow: 0, inComponent: 1)
        } else {
            textChild = optionsChild[pickerView.selectedRowInComponent(0)][row]
        }
        
        textField.text = "\(text) - \(textChild)"
    }
    
    func selectAndTrigger(row row: Int, component: Int) {
        pickerView(picker, didSelectRow: row, inComponent: component)
    }
    
    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }
    
    
}