如何调用UIPickerView inSwift的子类？

Question

我有一个ViewController，UIPickerView作为单个控件myPickerView，它属于类MyPickerView，是作为UIPickerView的子类创建的。我通过myPickerView调用ViewController viewDidLoad中的myPickerView.viewDidLoad。但是，这并不会执行MyPickerView的源函数。

我需要澄清一下我怎样才能做到这一点。我之所以使用MyPickerView，是因为它有很多特殊的代码，我不想把主ViewController弄乱。参见下面的示例代码：

import UIKit

class ViewController: UIViewController {

@IBOutlet weak var myPickerView: MyPickerView!
override func viewDidLoad() {
    super.viewDidLoad()
    myPickerView.viewDidLoad()
}

override func didReceiveMemoryWarning() {
    super.didReceiveMemoryWarning()
    // Dispose of any resources that can be recreated.
}


}


import UIKit
var gSep = ","
class MyPickerView: UIPickerView , UIPickerViewDataSource,     UIPickerViewDelegate {
var pickerData = [[" "],[" "]]
var category = [""]
var subCategory = [""]
var dictMenuList = [String:String]()

//MARK:- category/subcategory picker


func viewDidLoad() {
    println("MyPickerView: viewDidLoad")

    dictMenuList = ["Medical":"Sub-Cat 1.1,Sub-Cat 1.2,Sub-Cat 1.3,Sub-Cat 1.4,Sub-Cat 1.5,Sub-Cat 1.6,Sub-Cat 1.7",
        "Taxes": "Sub-Cat 2.1,Sub-Cat 2.2,Sub-Cat 2.3,Sub-Cat 2.4",
        "Bills": "Sub-Cat 3.1,Sub-Cat 3.2,Sub-Cat 3.3,Sub-Cat 3.4,Sub-Cat 3.5,Sub-Cat 3.6,Sub-Cat 3.7"]

    println("MyPickerView dictMenuList: \(dictMenuList)")



    self.reloadAllComponents()

    let firstKey = self.loadPickerWithCategory(0)
    self.loadPickerWithSubCategory(firstKey)

}


func numberOfComponentsInPickerView(pickerView: UIPickerView) -> Int {
    println("MyPickerView: numberOfComponentsInPickerView \(pickerData.count)")
    return pickerData.count
}

func pickerView(pickerView: UIPickerView, numberOfRowsInComponent component: Int) -> Int {
    return pickerData[component].count
}

func pickerView(pickerView: UIPickerView, didSelectRow row: Int, inComponent component: Int) {
    if component == 0 {
        let selectedKey = category[row]
        loadPickerWithSubCategory(selectedKey)
    }
}

func pickerView(pickerView: UIPickerView, titleForRow row: Int, forComponent component: Int) -> String! {
    return pickerData[component][row]
}

func pickerView(pickerView: UIPickerView, viewForRow row: Int, forComponent component: Int, reusingView view: UIView!) -> UIView
{
    var pickerLabel = UILabel()
    pickerLabel.textColor = UIColor.blackColor()
    pickerLabel.text = pickerData[component][row]
    pickerLabel.font = UIFont(name: pickerLabel.font.fontName, size: 17)
    pickerLabel.textAlignment = NSTextAlignment.Center
    return pickerLabel
}

func loadPickerWithCategory (row: Int) -> String{
    println("loadPickerWithCategory")
    category = [String](dictMenuList.keys)
    println("MyPickerView: category: \(category)")
    if category.isEmpty {
        return ""
    }
    let n1 = dictMenuList.count
    pickerData[0].removeAll(keepCapacity: true)
    for i in 0 ..< n1
    {
        pickerData[0].append(category[i])
    }
    return category[row]
}

func loadPickerWithSubCategory (key: String) {
    println("MyPickerView: loadPickerWithSubCategory")
    let x = dictMenuList[key]
    subCategory = x!.componentsSeparatedByString(gSep)
    let n1 = subCategory.count
    pickerData[1].removeAll(keepCapacity: true)
    if subCategory.isEmpty {
        return
    }
    for i in 0 ..< n1
    {
        pickerData[1].append(subCategory[i])
    }

    self.reloadAllComponents()
}

}

Answer 1

方法viewDidLoad是视图控制器方法，而不是视图方法。UIPickerView是UIView的子类，而不是UIViewController的子类，因此系统不会调用viewDidLoad方法。

您需要覆盖一个或多个init方法。

如果要从Storyboard或XIB加载选择器视图，则可能要重写initWithCoder。

如果要在代码中创建选择器，则可能要重写initWithFrame。

有时，我创建一个方法setup，我从initWithCoder:和initWithFrame:调用该方法。这样，无论如何加载视图对象，我的设置代码都会被调用。

我隐约记得在Swift中有一种更好的方法来处理这个决斗的初始化者问题，但是我不记得它是什么。(我还在学斯威夫特。)

编辑：

我突然意识到，在加载视图并设置了所有的输出后，您可以使用awakeFromNib方法进行安装。这大致相当于viewDidLoad对视图控制器的调用。我应该早点想到的。

(awakeFromNib是NSObject的一种方法，如果您不知道它的存在，就很难找到它。)

Answer 2

首先，viewDidLoad()是UIViewController类的一个方法，在控制器的视图加载到内存后调用。阅读更多的这里。您不能在视图中使用它。

因此，您应该在自定义选择器类中实现一个init方法。我建议重写initWithFrame和initWithCoder，并在那里设置组件。

您将像这样初始化您的自定义选择器：

myPickerView = MyPickerView(frame: yourFrame)