创建一个变量，该变量最终将保存所有方法使用的一段数据 [英] Creating a variable that will eventually hold a piece of data to be used by all methods

问题描述

我是 Objective-c 的新手，我只是想知道我将如何去做?我会创建一个常量并简单地填充它吗?

I am new to objective-c and I was just wondering how would I go about doing this? Would I create a constant and simply fill it?

示例

我有一个 NSString *date.我从互联网上获取了一些数据，现在我在这个变量中得到了我想要的日期.我希望能够随时使用此 NSString，而无需调用在我的程序中的任何范围内返回它的方法.

I have a NSString *date. I fetch some data from the internet and now I have the date I want in this variable. I want to be able to use this NSString at anytime without calling a method that returns it at any scope within my program.

提前致谢！

决定使用基于答案的单例...

Decided to use singletons based on answer...

我应该把代码放在哪里来从互联网上检索变量将保存的日期?会在这里吗?

Where would I put the code to retrieve the date from the internet that the variable will hold? Would it be here?

   static SingletonClass *sharedInstance = nil;

  // Get the shared instance and create it if necessary.
  + (SingletonClass *)sharedInstance {
if (sharedInstance == nil) {
    sharedInstance = [[super allocWithZone:NULL] init];
}

//Put Code here??

 return sharedInstance;
   } 

推荐答案

如果您所做的只是存储单个日期变量，我建议使用 NSUserDefaults.如果您使用单例，则无论如何您都必须在启动之间保留数据.和 NSUserDefaults 是一个单例.如果您创建一个单例，那么您将创建另一个类等等.

if all your doing is storing a single date variable, I would suggest using NSUserDefaults. if you use a singleton then you'll have to persist the data between launches anyways. and NSUserDefaults is a singleton. If you create a singleton then you'll to create another class and so forth.

存储:

NSDate *updateDate = [NSDate date];
[[NSUserDefaults standardUserDefaults] updateDate forKey:@"lastUpdateDate"];
[[NSUserDefaults standardUserDefaults] synchronize];

检索:

NSDate *updateDate = [[NSUserDefaults standardUserDefaults] dateForKey:@"lastUpdateDate"];

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