如何在Swift中使用多个组件更改UIPickerView的文本颜色？

Question

下面的代码将更改所有3个组件的选择器视图的字体颜色。但是，当我尝试旋转车轮时会崩溃。我认为这与didSelectRow函数有关。也许这两个功能必须以某种方式嵌套？任何想法？

    func pickerView(pickerView: UIPickerView, attributedTitleForRow row: Int, forComponent component: Int) -> NSAttributedString? {
    var attributedString: NSAttributedString!
    if component == 0 {
        attributedString = NSAttributedString(string: a.text!, attributes: [NSForegroundColorAttributeName : UIColor.redColor()])
    }
    if component == 1 {
        attributedString = NSAttributedString(string: b.text!, attributes: [NSForegroundColorAttributeName : UIColor.redColor()])
    }
    if component == 2 {
        attributedString = NSAttributedString(string: c.text!, attributes: [NSForegroundColorAttributeName : UIColor.redColor()])
    }
    return attributedString
}


func pickerView(pickerView: UIPickerView, didSelectRow row: Int, inComponent component: Int){

    switch component {
    case 0:
        aOutput.text = a[row]      -->  **Code breaks**
    case 1:
        bOutput.text = b[row]
    case 2:
        cOutput.text = c[row]
    default:
        10
    }

Answer 1

以下pickerView:attributedTitleForRow:forComponent:方法实现应为您提供帮助：

func pickerView(pickerView: UIPickerView, attributedTitleForRow row: Int, forComponent component: Int) -> NSAttributedString? {
    let attributedString = NSAttributedString(string: "some string", attributes: [NSForegroundColorAttributeName : UIColor.redColor()])
    return attributedString
}

更新资料

如果要attributedString在多个if或switch语句中使用，下面的UIViewControllersubClass示例将为您提供帮助：

import UIKit

class ViewController: UIViewController, UIPickerViewDelegate, UIPickerViewDataSource {

    @IBOutlet weak var picker: UIPickerView!

    let arrayOne = ["One", "Two", "Three", "Four", "Five", "Six"]
    let arrayTwo = ["Un", "Deux", "Trois", "Quatre", "Cinq", "Six"]
    let arrayThree = [1, 2, 3, 4, 5, 6]


    override func viewDidLoad() {
        super.viewDidLoad()

        picker.delegate = self
        picker.dataSource = self
    }

    func numberOfComponentsInPickerView(_: UIPickerView) -> Int {
        return 3
    }

    func pickerView(_: UIPickerView, numberOfRowsInComponent component: Int) -> Int {
        switch component {
        case 0:
            return arrayOne.count
        case 1:
            return arrayTwo.count
        case 2:
            return arrayThree.count
        default:
            return NSNotFound
        }
    }

    func pickerView(pickerView: UIPickerView, attributedTitleForRow row: Int, forComponent component: Int) -> NSAttributedString? {
        var attributedString: NSAttributedString!

        switch component {
        case 0:
            attributedString = NSAttributedString(string: arrayOne[row], attributes: [NSForegroundColorAttributeName : UIColor.redColor()])
        case 1:
            attributedString = NSAttributedString(string: arrayTwo[row], attributes: [NSForegroundColorAttributeName : UIColor.redColor()])
        case 2:
            attributedString = NSAttributedString(string: toString(arrayThree[row]), attributes: [NSForegroundColorAttributeName : UIColor.redColor()])
        default:
            attributedString = nil
        }

        return attributedString
    }

    func pickerView(_: UIPickerView, didSelectRow row: Int, inComponent component: Int) {
        switch component {
        case 0:
            println(arrayOne[row])
        case 1:
            println(arrayTwo[row])
        case 2:
            println(arrayThree[row])
        default:
            break
        }
    }

}