跨选项卡栏应用程序同步plist [英] Synchronizing plist across a Tab Bar Application

问题描述

我有一个包含三个选项卡的应用程序，该应用程序共享一个用于连接信息(客户端ID，服务器地址，端口号)的plist.在每个视图控制器中，都会在viewDidLoad方法中初始化一个NSUserDefaults对象:

I have a three tab application that shares a plist for connection information (Client ID, Server Address, Port Number). In each of the view controllers, an NSUserDefaults object is initialized within the viewDidLoad method:

- (void)viewDidLoad {
    [super viewDidLoad];

    // load default settings into class instance variables
    defaults = [NSUserDefaults standardUserDefaults];
    self.clientID = [defaults objectForKey:@"clientID"];
    self.serverAddress = [defaults objectForKey:@"serverAddress"];
    self.serverPort = [defaults objectForKey:@"serverPort"];
}

我的一个视图代表一个设置"页面，该页面允许用户更改plist.但是，更新plist时，更改不会反映在所有选项卡视图中，因为每个对象都需要同步:

One of my views represents a "Settings" page that allows a user to make changes to the plist. However, when the plist is updated, the changes aren't reflected across all of the tab views because a synchronize is needed for each of the objects:

[defaults synchronize];

我了解到viewDidLoad方法在应用程序的生命周期内仅被调用一次(至少对于Tab Bar应用程序而言)，因此，我无法在此处放置同步调用.然后，我转到AppDelegate类，发现了tabBarController方法.如何使用此方法在所有视图控制器之间同步NSUserDefaults对象，而无需使用同步按钮?这是打开应用程序时共享/调整首选项的正确方法吗?

I've learned that the viewDidLoad method is only called once during the lifetime of an application (at least for a Tab Bar application), so, I can't put the synchronize calls here. I then turned to the AppDelegate class and discovered the tabBarController method. How do I use this method to synchronize the NSUserDefaults objects across all view controllers without the need for a sync button? Is this even the correct way of sharing/adjusting preferences while an application is open?

我现在在这里:

- (void)tabBarController:(UITabBarController *)tabBarController didSelectViewController:(UIViewController *)viewController {

    // I need to synchronize somewhere in here???
    switch (tabBarController.selectedIndex)
    {
    case 0:
        NSLog(@"Tab 0 selected");
        break;
    case 1:
        NSLog(@"Tab 1 selected");
        break;
    case 2:
        NSLog(@"Tab 2 Selected");
        break;
    }
}

提前谢谢.

推荐答案

尝试同步viewWillAppear(而不是viewDidLoad)中的默认值.

Try syncing the defaults in viewWillAppear instead of viewDidLoad.

例如，如果存在内存问题，可能会多次调用viewDidLoad(在这种情况下，将在两次之间调用viewDidUnload).

It may happen that viewDidLoad is called multiple times (in which case, viewDidUnload will have been called between), for example, if there is a memory issue.

通过同步viewWillAppear中的默认值，可以确保相关的UIViewController在成为选定的视图控制器之前得到更新.

By synchronizing the defaults in viewWillAppear, you are ensuring that the relevant UIViewController is updated just before it becomes the selected view controller.

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