Ios 如何在阵列中放置Firebase数据的节点
在我的应用程序的第一页,我正在使用UIViewPicker,它允许用户选择他们想要选择的国家。而不是我通过如下所示的数组将国家名称硬编码到UIPicker中:Ios 如何在阵列中放置Firebase数据的节点,ios,swift,firebase,Ios,Swift,Firebase,在我的应用程序的第一页,我正在使用UIViewPicker,它允许用户选择他们想要选择的国家。而不是我通过如下所示的数组将国家名称硬编码到UIPicker中: var country = ["USA", "CANADA"] 我决定最好是该应用程序能够访问我的firebase数据库,在那里它可以获取所有的国家,并将它们附加到数组中,UIPicker可以从中读取数据 这样,如果我想增加更多的国家,我就不必发布新版本的应用程序。我只需在数据库中添加另一个国家,应用程序就会自动更新它。但我不太清楚如何
var country = ["USA", "CANADA"]
我决定最好是该应用程序能够访问我的firebase数据库,在那里它可以获取所有的国家,并将它们附加到数组中,UIPicker可以从中读取数据
这样,如果我想增加更多的国家,我就不必发布新版本的应用程序。我只需在数据库中添加另一个国家,应用程序就会自动更新它。但我不太清楚如何做到这一点。当我打印数据库的快照时,我得到了整个数据库,但我只想将美国和加拿大放入一个数组中
下面是我的firebase数据库的结构:
countries
Canada
states
Alberta
British Columbia
USA
states
Alabama
Arkansas
这是我目前的代码:
import UIKit
import FirebaseDatabase
class ViewController: UIViewController, UIPickerViewDelegate, UIPickerViewDataSource {
@IBOutlet weak var countryPicker: UIPickerView!
//let country = ["USA", "Canada"] I am no longer using this hardcoded array
var countrySelected = String()
var action = 0
override func viewDidLoad() {
super.viewDidLoad()
//this is where I reach out to the database
let database = Database.database().reference()
database.child("countries").observeSingleEvent(of: .value) { (Snapshot) in
print(Snapshot)
}
//add code here that takes the snapshot and appends the the array below
var country = string()
countrySelected = country[0]
countryPicker.selectRow(action, inComponent: 0, animated: false)
//print(countrySelected)
}
func numberOfComponents(in pickerView: UIPickerView) -> Int {
return 1
}
func pickerView(_ pickerView: UIPickerView, numberOfRowsInComponent component: Int) -> Int {
return country.count
}
func pickerView(_ pickerView: UIPickerView, titleForRow row: Int, forComponent component: Int) -> String? {
return country[row]
}
func pickerView(_ pickerView: UIPickerView, didSelectRow row: Int, inComponent component: Int) {
countrySelected = country[row]
action = country.firstIndex(of: countrySelected)!
//print(countrySelected)
}
}
如果有人能帮忙解释,那就太棒了 为了简化工作,我们可以创建一些结构来表示国家和州
struct Country {
struct State {
let country: String
let name: String
}
let name: String
let states: [State]
static var ref: DatabaseReference {
return Database.database().reference(withPath: "countries")
}
static func from(key: String, value: Any?) -> Country? {
guard
let value = value as? [String:[String]],
let states = value["states"] else { return nil }
return Country(name: key, states: states.map {
State(country: key, name: $0)
})
}
static func countries(from snapshot: DataSnapshot) -> [Country]? {
return snapshot.snapshots.compactMap {
Country.from(key: $0.key, value: $0.value)
}
}
}
以及DataSnapshot的扩展,为快照的子对象提供了方便的访问器
extension DataSnapshot {
var snapshots: [DataSnapshot] {
return children.allObjects as? [DataSnapshot] ?? []
}
}
接下来,我们创建一些属性来处理国家/地区–一个存储它们的数组和一些计算属性以返回所选国家/地区和州
class CountryStatePickerViewController: UIViewController {
// MARK: Outlets
@IBOutlet weak var pickerView: UIPickerView! {
didSet {
loadCountries()
}
}
// MARK: Properties
private var countries = [Country]() {
didSet {
pickerView.reloadAllComponents()
}
}
var selectedCountry: Country? {
return country(at: pickerView.selectedRow(inComponent: 0))
}
var selectedState: Country.State? {
return selectedCountry.flatMap {
state(at: pickerView.selectedRow(inComponent: 1), in: $0)
}
}
}
我们还需要一些方法来安全地访问特定索引中的国家和州,以及首先加载这些国家的方法
extension DataSnapshot {
var snapshots: [DataSnapshot] {
return children.allObjects as? [DataSnapshot] ?? []
}
}
extension CountryStatePickerViewController {
private func loadCountries() {
Country.ref.observeSingleEvent(of: .value, with: { [weak self] in
self?.countries = Country.countries(from: $0) ?? []
})
}
private func country(at index: Int) -> Country? {
return countries.indices.contains(index) ? countries[index] : nil
}
private func state(at index: Int, in country: Country) -> Country.State? {
return country.states.indices.contains(index) ? country.states[index] : nil
}
}
最后,在我们的UIPickerView协议一致性中,countries数组填充数据源。我们可以使用两个组件来表示国家及其对应的状态
extension CountryStatePickerViewController: UIPickerViewDataSource, UIPickerViewDelegate {
func numberOfComponents(in pickerView: UIPickerView) -> Int {
return 2
}
func pickerView(_ pickerView: UIPickerView, numberOfRowsInComponent component: Int) -> Int {
switch component {
case 0:
return countries.count
case 1:
return selectedCountry?.states.count ?? 0
default:
return 0
}
}
func pickerView(_ pickerView: UIPickerView, titleForRow row: Int, forComponent component: Int) -> String? {
switch component {
case 0:
return country(at: row)?.name
case 1:
return selectedCountry.flatMap { state(at: row, in: $0)?.name }
default:
return nil
}
}
func pickerView(_ pickerView: UIPickerView, didSelectRow row: Int, inComponent component: Int) {
if component == 0 { pickerView.reloadComponent(1) }
selectedState.flatMap { print($0.name, $0.country) }
}
}
简单地将数据从firebase实现为数组似乎很复杂。好的,我删除了数据提供程序抽象,我们只使用struct处理数据快照解析并帮助表示picker view数据源。到目前为止,我有:Database.Database.reference.childcountries.observe.childAdded,带有:{printcountry中的快照找到printSnapshot},使用取消:nil抱歉延迟响应,我希望它已被修复。您得到错误,因为我们获得了任何对象的数组,因此需要将其类型转换为字符串,如country[row]as?string
var countries : [Any] = []
override func viewDidLoad() {
super.viewDidLoad()
database.child("countries").observeSingleEvent(of: .value) { (snapshot) in
if snapshot.exists() {
if let dict : [String : AnyObject] = snapshot.value as? [String : AnyObject] {
let array : [Any] = (dict as AnyObject).allValues
self.countries = array
// reload countryPicker data
}
}
else {
// not exist in db
}
}
}