Ios 如何在Swift中的视图控制器和其他对象之间共享数据？

假设我的Swift应用程序中有多个视图控制器，我希望能够在它们之间传递数据。如果我在一个视图控制器堆栈中处于几层以下，如何将数据传递给另一个视图控制器？或者在选项卡栏视图控制器中的选项卡之间

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（注意，这个问题是一个“振铃器”。）它被问得太多了，以至于我决定写一篇关于这个主题的教程。请看下面我的答案。

这个问题一直都会出现

一个建议是创建一个数据容器singleton：一个在应用程序生命周期中只创建一次的对象，并在应用程序生命周期中保持不变

这种方法非常适用于需要在应用程序中的不同类之间提供/修改全局应用程序数据的情况

其他方法（如在视图控制器之间设置单向或双向链接）更适合在视图控制器之间直接传递信息/消息的情况

（其他备选方案见下文nhgrif的答案。）

使用数据容器singleton，可以向类中添加一个属性，该属性存储对singleton的引用，然后在需要访问时随时使用该属性

您可以设置singleton，使其将内容保存到磁盘，以便在两次启动之间保持应用程序状态

我在GitHub上创建了一个演示项目，演示了如何做到这一点。以下是链接：

以下是该项目的自述：

SwiftDataContainerSingleton 演示如何使用数据容器单例保存应用程序状态并在对象之间共享

DataContainerSingleton

类是实际的单例

它使用一个静态常量

sharedDataContainer

保存对singleton的引用

要访问singleton，请使用以下语法

DataContainerSingleton.sharedDataContainer

示例项目在数据容器中定义了3个属性：

  var someString: String?
  var someOtherString: String?
  var someInt: Int?

要从数据容器加载

someInt

属性，可以使用如下代码：

let theInt = DataContainerSingleton.sharedDataContainer.someInt

goToBackgroundObserver = NSNotificationCenter.defaultCenter().addObserverForName(
  UIApplicationDidEnterBackgroundNotification,
  object: nil,
  queue: nil)
  {
    (note: NSNotification!) -> Void in
    let defaults = NSUserDefaults.standardUserDefaults()
    //-----------------------------------------------------------------------------
    //This code saves the singleton's properties to NSUserDefaults.
    //edit this code to save your custom properties
    defaults.setObject( self.someString, forKey: DefaultsKeys.someString)
    defaults.setObject( self.someOtherString, forKey: DefaultsKeys.someOtherString)
    defaults.setObject( self.someInt, forKey: DefaultsKeys.someInt)
    //-----------------------------------------------------------------------------

    //Tell NSUserDefaults to save to disk now.
    defaults.synchronize()
}

let defaults = NSUserDefaults.standardUserDefaults()
//-----------------------------------------------------------------------------
//This code reads the singleton's properties from NSUserDefaults.
//edit this code to load your custom properties
someString = defaults.objectForKey(DefaultsKeys.someString) as! String?
someOtherString = defaults.objectForKey(DefaultsKeys.someOtherString) as! String?
someInt = defaults.objectForKey(DefaultsKeys.someInt) as! Int?
//-----------------------------------------------------------------------------

struct DefaultsKeys
{
  static let someString  = "someString"
  static let someOtherString  = "someOtherString"
  static let someInt  = "someInt"
}

DefaultsKeys.someInt

要将值保存到someInt，请使用以下语法：

DataContainerSingleton.sharedDataContainer.someInt = 3

DataContainerSingleton的

init

方法为

UIApplicationIdentinterBackgroundNotification

添加了一个观察者。该代码如下所示：

let theInt = DataContainerSingleton.sharedDataContainer.someInt

goToBackgroundObserver = NSNotificationCenter.defaultCenter().addObserverForName(
  UIApplicationDidEnterBackgroundNotification,
  object: nil,
  queue: nil)
  {
    (note: NSNotification!) -> Void in
    let defaults = NSUserDefaults.standardUserDefaults()
    //-----------------------------------------------------------------------------
    //This code saves the singleton's properties to NSUserDefaults.
    //edit this code to save your custom properties
    defaults.setObject( self.someString, forKey: DefaultsKeys.someString)
    defaults.setObject( self.someOtherString, forKey: DefaultsKeys.someOtherString)
    defaults.setObject( self.someInt, forKey: DefaultsKeys.someInt)
    //-----------------------------------------------------------------------------

    //Tell NSUserDefaults to save to disk now.
    defaults.synchronize()
}

let defaults = NSUserDefaults.standardUserDefaults()
//-----------------------------------------------------------------------------
//This code reads the singleton's properties from NSUserDefaults.
//edit this code to load your custom properties
someString = defaults.objectForKey(DefaultsKeys.someString) as! String?
someOtherString = defaults.objectForKey(DefaultsKeys.someOtherString) as! String?
someInt = defaults.objectForKey(DefaultsKeys.someInt) as! Int?
//-----------------------------------------------------------------------------

struct DefaultsKeys
{
  static let someString  = "someString"
  static let someOtherString  = "someOtherString"
  static let someInt  = "someInt"
}

DefaultsKeys.someInt

在观察者代码中，它将数据容器的属性保存到

NSUserDefaults

。您还可以使用

NSCoding

、核心数据或各种其他方法来保存状态数据

DataContainerSingleton的

init

方法还尝试为其属性加载保存的值

init方法的这一部分如下所示：

let theInt = DataContainerSingleton.sharedDataContainer.someInt

goToBackgroundObserver = NSNotificationCenter.defaultCenter().addObserverForName(
  UIApplicationDidEnterBackgroundNotification,
  object: nil,
  queue: nil)
  {
    (note: NSNotification!) -> Void in
    let defaults = NSUserDefaults.standardUserDefaults()
    //-----------------------------------------------------------------------------
    //This code saves the singleton's properties to NSUserDefaults.
    //edit this code to save your custom properties
    defaults.setObject( self.someString, forKey: DefaultsKeys.someString)
    defaults.setObject( self.someOtherString, forKey: DefaultsKeys.someOtherString)
    defaults.setObject( self.someInt, forKey: DefaultsKeys.someInt)
    //-----------------------------------------------------------------------------

    //Tell NSUserDefaults to save to disk now.
    defaults.synchronize()
}

let defaults = NSUserDefaults.standardUserDefaults()
//-----------------------------------------------------------------------------
//This code reads the singleton's properties from NSUserDefaults.
//edit this code to load your custom properties
someString = defaults.objectForKey(DefaultsKeys.someString) as! String?
someOtherString = defaults.objectForKey(DefaultsKeys.someOtherString) as! String?
someInt = defaults.objectForKey(DefaultsKeys.someInt) as! Int?
//-----------------------------------------------------------------------------

struct DefaultsKeys
{
  static let someString  = "someString"
  static let someOtherString  = "someOtherString"
  static let someInt  = "someInt"
}

DefaultsKeys.someInt

用于将值加载和保存到NSUserDefaults中的键存储为字符串常量，这些常量是struct

DefaultsKeys

的一部分，定义如下：

let theInt = DataContainerSingleton.sharedDataContainer.someInt

goToBackgroundObserver = NSNotificationCenter.defaultCenter().addObserverForName(
  UIApplicationDidEnterBackgroundNotification,
  object: nil,
  queue: nil)
  {
    (note: NSNotification!) -> Void in
    let defaults = NSUserDefaults.standardUserDefaults()
    //-----------------------------------------------------------------------------
    //This code saves the singleton's properties to NSUserDefaults.
    //edit this code to save your custom properties
    defaults.setObject( self.someString, forKey: DefaultsKeys.someString)
    defaults.setObject( self.someOtherString, forKey: DefaultsKeys.someOtherString)
    defaults.setObject( self.someInt, forKey: DefaultsKeys.someInt)
    //-----------------------------------------------------------------------------

    //Tell NSUserDefaults to save to disk now.
    defaults.synchronize()
}

let defaults = NSUserDefaults.standardUserDefaults()
//-----------------------------------------------------------------------------
//This code reads the singleton's properties from NSUserDefaults.
//edit this code to load your custom properties
someString = defaults.objectForKey(DefaultsKeys.someString) as! String?
someOtherString = defaults.objectForKey(DefaultsKeys.someOtherString) as! String?
someInt = defaults.objectForKey(DefaultsKeys.someInt) as! Int?
//-----------------------------------------------------------------------------

struct DefaultsKeys
{
  static let someString  = "someString"
  static let someOtherString  = "someOtherString"
  static let someInt  = "someInt"
}

DefaultsKeys.someInt

您可以这样引用其中一个常量：

let theInt = DataContainerSingleton.sharedDataContainer.someInt

goToBackgroundObserver = NSNotificationCenter.defaultCenter().addObserverForName(
  UIApplicationDidEnterBackgroundNotification,
  object: nil,
  queue: nil)
  {
    (note: NSNotification!) -> Void in
    let defaults = NSUserDefaults.standardUserDefaults()
    //-----------------------------------------------------------------------------
    //This code saves the singleton's properties to NSUserDefaults.
    //edit this code to save your custom properties
    defaults.setObject( self.someString, forKey: DefaultsKeys.someString)
    defaults.setObject( self.someOtherString, forKey: DefaultsKeys.someOtherString)
    defaults.setObject( self.someInt, forKey: DefaultsKeys.someInt)
    //-----------------------------------------------------------------------------

    //Tell NSUserDefaults to save to disk now.
    defaults.synchronize()
}

let defaults = NSUserDefaults.standardUserDefaults()
//-----------------------------------------------------------------------------
//This code reads the singleton's properties from NSUserDefaults.
//edit this code to load your custom properties
someString = defaults.objectForKey(DefaultsKeys.someString) as! String?
someOtherString = defaults.objectForKey(DefaultsKeys.someOtherString) as! String?
someInt = defaults.objectForKey(DefaultsKeys.someInt) as! Int?
//-----------------------------------------------------------------------------

struct DefaultsKeys
{
  static let someString  = "someString"
  static let someOtherString  = "someOtherString"
  static let someInt  = "someInt"
}

DefaultsKeys.someInt

使用数据容器单例： 这个示例应用程序简单地使用了数据容器singleton

有两个视图控制器。第一个是UIViewController

ViewController

的自定义子类，第二个是UIViewController

SecondVC

的自定义子类

两个视图控制器上都有一个文本字段，并且都将数据容器singlelton的

someInt

属性中的值加载到其

viewwillbeen

方法中的文本字段中，并且都将文本字段中的当前值保存回数据容器的“someInt”中

将值加载到文本字段中的代码位于

视图中将出现：

方法：

override func viewWillAppear(animated: Bool)
{
  //Load the value "someInt" from our shared ata container singleton
  let value = DataContainerSingleton.sharedDataContainer.someInt ?? 0
  
  //Install the value into the text field.
  textField.text =  "\(value)"
}

将用户编辑的值保存回数据容器的代码位于视图控制器的

文本字段shouldenediting

方法中：

 func textFieldShouldEndEditing(textField: UITextField) -> Bool
 {
   //Save the changed value back to our data container singleton
   DataContainerSingleton.sharedDataContainer.someInt = textField.text!.toInt()
   return true
 }

---

您应该将值加载到用户界面的ViewWillDisplay中，而不是viewDidLoad中，这样每次显示视图控制器时，您的UI都会更新。

这个问题总是会出现

一个建议是创建一个数据容器singleton：一个在应用程序生命周期中只创建一次的对象，并在应用程序生命周期中保持不变

这种方法非常适用于需要在应用程序中的不同类之间提供/修改全局应用程序数据的情况

其他方法（如在视图控制器之间设置单向或双向链接）更适合在视图控制器之间直接传递信息/消息的情况

（其他备选方案见下文nhgrif的答案。）

使用数据容器singleton，可以向类中添加一个属性，该属性存储对singleton的引用，然后在需要访问时随时使用该属性

您可以设置singleton，使其将内容保存到磁盘，以便在两次启动之间保持应用程序状态

我在GitHub上创建了一个演示项目，演示了如何做到这一点。以下是链接：

以下是该项目的自述：

SwiftDataContainerSingleton 演示如何使用数据容器单例保存应用程序状态并在对象之间共享

DataContainerSingleton

类是实际的单例

它使用一个静态常量

sharedDataContainer

保存对singleton的引用

要访问singleton，请使用以下语法

DataContainerSingleton.sharedDataContainer

示例项目在数据容器中定义了3个属性：

  var someString: String?
  var someOtherString: String?
  var someInt: Int?

要从数据容器加载

someInt

属性，可以使用如下代码：

let theInt = DataContainerSingleton.sharedDataContainer.someInt

goToBackgroundObserver = NSNotificationCenter.defaultCenter().addObserverForName(
  UIApplicationDidEnterBackgroundNotification,
  object: nil,
  queue: nil)
  {
    (note: NSNotification!) -> Void in
    let defaults = NSUserDefaults.standardUserDefaults()
    //-----------------------------------------------------------------------------
    //This code saves the singleton's properties to NSUserDefaults.
    //edit this code to save your custom properties
    defaults.setObject( self.someString, forKey: DefaultsKeys.someString)
    defaults.setObject( self.someOtherString, forKey: DefaultsKeys.someOtherString)
    defaults.setObject( self.someInt, forKey: DefaultsKeys.someInt)
    //-----------------------------------------------------------------------------

    //Tell NSUserDefaults to save to disk now.
    defaults.synchronize()
}

let defaults = NSUserDefaults.standardUserDefaults()
//-----------------------------------------------------------------------------
//This code reads the singleton's properties from NSUserDefaults.
//edit this code to load your custom properties
someString = defaults.objectForKey(DefaultsKeys.someString) as! String?
someOtherString = defaults.objectForKey(DefaultsKeys.someOtherString) as! String?
someInt = defaults.objectForKey(DefaultsKeys.someInt) as! Int?
//-----------------------------------------------------------------------------

struct DefaultsKeys
{
  static let someString  = "someString"
  static let someOtherString  = "someOtherString"
  static let someInt  = "someInt"
}

DefaultsKeys.someInt

要将值保存到someInt，请使用以下语法：

DataContainerSingleton.sharedDataContainer.someInt = 3

DataContainerSingleton的

init

方法为

UIApplicationIdentinterBackgroundNotification

添加了一个观察者。该代码如下所示：

let theInt = DataContainerSingleton.sharedDataContainer.someInt

goToBackgroundObserver = NSNotificationCenter.defaultCenter().addObserverForName(
  UIApplicationDidEnterBackgroundNotification,
  object: nil,
  queue: nil)
  {
    (note: NSNotification!) -> Void in
    let defaults = NSUserDefaults.standardUserDefaults()
    //-----------------------------------------------------------------------------
    //This code saves the singleton's properties to NSUserDefaults.
    //edit this code to save your custom properties
    defaults.setObject( self.someString, forKey: DefaultsKeys.someString)
    defaults.setObject( self.someOtherString, forKey: DefaultsKeys.someOtherString)
    defaults.setObject( self.someInt, forKey: DefaultsKeys.someInt)
    //-----------------------------------------------------------------------------

    //Tell NSUserDefaults to save to disk now.
    defaults.synchronize()
}

let defaults = NSUserDefaults.standardUserDefaults()
//-----------------------------------------------------------------------------
//This code reads the singleton's properties from NSUserDefaults.
//edit this code to load your custom properties
someString = defaults.objectForKey(DefaultsKeys.someString) as! String?
someOtherString = defaults.objectForKey(DefaultsKeys.someOtherString) as! String?
someInt = defaults.objectForKey(DefaultsKeys.someInt) as! Int?
//-----------------------------------------------------------------------------

struct DefaultsKeys
{
  static let someString  = "someString"
  static let someOtherString  = "someOtherString"
  static let someInt  = "someInt"
}

DefaultsKeys.someInt

在观察者代码中，它将数据容器的属性保存到

NSUserDefaults

。您还可以使用

NSCoding

、核心数据或各种其他方法来保存状态数据。