Take data from Enum to show on UIPickerView

问题

I am creating a simple View where there is a UIPickerView and I want to display the choices on the PickerView from an enum. I have created an enum of possible drinks

enum drink{
  case coffee
  case tea
  case cola
  case water
}

I was wondering how it would be possible to display the drinks in an UIPickerView? I am using Swift 1.2 and Xcode 6.3.1.. Thanks!! :)

回答1:

As mentioned by ABakerSmith you can use the Printable protocol to display the String in the UIPickerView.

In the end you can have a ViewController looking as the following:

//
//  ViewController.swift
//  Test
//
//  Created by Stefan Veis Pennerup on 04/05/15.
//  Copyright (c) 2015 Kumuluzz. All rights reserved.
//

import UIKit

class ViewController: UIViewController, UIPickerViewDataSource, UIPickerViewDelegate {

@IBOutlet weak var pickerView: UIPickerView!

enum Drink: Int, Printable {
    case Coffee = 0
    case Tea = 1
    case Cola = 2
    case Water = 3
    static var count: Int { return Drink.Water.hashValue + 1 }

    var description: String {
        switch self {
        case .Coffee: return "Coffee"
        case .Tea   : return "Tea"
        case .Cola  : return "Cola"
        case .Water : return "Water"
        default: return ""
        }
    }
}

// MARK: - UIPickerViewDataSource

func numberOfComponentsInPickerView(pickerView: UIPickerView) -> Int {
    return 1
}

func pickerView(pickerView: UIPickerView, numberOfRowsInComponent component: Int) -> Int {
    return Drink.count.hashValue
}

// MARK: - UIPickerViewDelegate

func pickerView(pickerView: UIPickerView, titleForRow row: Int, forComponent component: Int) -> String! {
    return Drink(rawValue: row)?.description;
}

// several optional methods:

// func pickerView(pickerView: UIPickerView!, widthForComponent component: Int) -> CGFloat

// func pickerView(pickerView: UIPickerView!, rowHeightForComponent component: Int) -> CGFloat

// func pickerView(pickerView: UIPickerView!, attributedTitleForRow row: Int, forComponent component: Int) -> NSAttributedString!

// func pickerView(pickerView: UIPickerView!, viewForRow row: Int, forComponent component: Int, reusingView view: UIView!) -> UIView!

// func pickerView(pickerView: UIPickerView!, didSelectRow row: Int, inComponent component: Int)
}

回答2:

Give them a String and call it with rawValue.

enum Drink: String {
    case Coffee = "Coffee"
    case Tea = "Tea"
    case Cola = "Cola"
    case Water = "Water"
}

println(Drink.Coffee.rawValue) // Prints "Coffee"

As ABakerSmith mentioned in his answer, you can use printable as well. In the next example it's a little different compared to the approach of ABakerSmith's.

enum Drink: String, Printable {
    case Coffee = "Coffee"
    case Tea = "Tea"
    case Cola = "Cola"
    case Water = "Water"

    var description: String { return rawValue }
}

println(Drink.Coffee) // Prints "Coffee"

As Leonardo Savio Dabus mentioned, a simplified version.

回答3:

I would make Drink conform to the Printable protocol:

The Printable protocol looks like:

protocol Printable {
    var description: String { get }
}

Therefore, your Drink enum would be:

enum Drink : Printable {
    case Coffee
    case Tea
    case Cola
    case Water

    var description: String {
        switch self {
            case .Coffee: return "Coffee"
            case .Tea   : return "Tea"
            case .Cola  : return "Cola"
            case .Water : return "Water"
        }
    }
}

And here's an example of using a Drink in a String:

let myDrink: Drink = .Tea
println("I'm drinking \(myDrink)") // I'm drinking Tea

回答4:

Apple introduced CaseIterable in Swift 4.2 / Xcode 10+ which makes this cleaner.

The compiler can automatically provide an implementation of the CaseIterable requirements for any enumeration without associated values or @available attributes on its cases. The synthesized allCases collection provides the cases in order of their declaration.

Example:

enum Drink: String, CaseIterable {
    case coffee = "Coffee"
    case tea = "Tea"
    case cola = "Cola"
    case water = "Water"
}

extension ViewController: UIPickerViewDelegate {
    func pickerView(_ pickerView: UIPickerView, titleForRow row: Int, forComponent component: Int) -> String? {
        return Drink.allCases[row].rawValue
    }
}

extension ViewController: UIPickerViewDataSource {
    func numberOfComponents(in pickerView: UIPickerView) -> Int {
        return 1
    }

    func pickerView(_ pickerView: UIPickerView, numberOfRowsInComponent component: Int) -> Int {
        return Drink.allCases.count
    }
}

You can find a full example using a UITextField on Github

回答5:

You can use enum like this way;

enum drink: String{
    case coffee = "coffee"
    case tea = "tea"
    case cola = "cola"
    case water = "water" 
}

You can add uipickerview in this example;

http://makeapppie.com/tag/uipickerview-in-swift/

来源：https://stackoverflow.com/questions/30025481/take-data-from-enum-to-show-on-uipickerview

标签

ios

swift

enums

uipickerview