ios Objective-c 中 Singleton 类的用途是什么？
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What is the use of Singleton class in objective-c?
提问by liza
I know Singleton class is a class whose only one object can be created at a time.
我知道 Singleton 类是一次只能创建一个对象的类。
My questions are:
我的问题是：
1.What isthe use of Singleton class in objective-c?
1.什么是Objective-C中使用Singleton类的？
2.How tocreate and use the created Singleton class?
2、如何创建和使用创建的Singleton类？
回答by Rui Peres
You normally use a Singleton when you want to expose something to the entire project, or you want a single point of entry to something. Imagine that you have a photos application, and 3 our 4 UIViewControllersneed to access an Array with Photos. It might(most of the time it doesn't) make sense to have a Singleton to have a reference to those photos.
当您想要向整个项目公开某些内容，或者您想要某个内容的单一入口点时，通常会使用 Singleton。想象一下，您有一个照片应用程序，并且 3 我们的 4UIViewControllers需要访问带有照片的数组。让单身人士引用这些照片可能（大多数时候没有）有意义。
A quick implementation can be found here. And would look like this:
可以在此处找到快速实现。看起来像这样：
+ (id)sharedManager
{
static id sharedManager;
static dispatch_once_t once;
dispatch_once(&once, ^{
sharedManager = [[self alloc] init];
});
return sharedManager;
}
You can see other ways of implementing this pattern here.
您可以在此处查看实现此模式的其他方法。
In Swift 2.1 would look like this:
在 Swift 2.1 中看起来像这样：
class Manager {
static let sharedManager = Manager()
private init() { }
}
回答by Vineet Singh
A singleton is a special kind of class where only one instance of the class exists for the current process. In the case of an iPhone app, the one instance is shared across the entire app.
单例是一种特殊的类，其中当前进程只存在该类的一个实例。对于 iPhone 应用程序，一个实例在整个应用程序中共享。
Have a look at these tutorials :
看看这些教程：
http://www.codeproject.com/Tips/232321/Implement-Objective-C-Singleton-Pattern
http://www.codeproject.com/Tips/232321/Implement-Objective-C-Singleton-Pattern
http://xcodenoobies.blogspot.in/2012/08/how-to-pass-data-between.html
http://xcodenoobies.blogspot.in/2012/08/how-to-pass-data-between.html
http://www.johnwordsworth.com/2010/04/iphone-code-snippet-the-singleton-pattern/
http://www.johnwordsworth.com/2010/04/iphone-code-snippet-the-singleton-pattern/
http://www.idev101.com/code/Objective-C/singletons.html
http://www.idev101.com/code/Objective-C/singletons.html
And this video tutorial :
还有这个视频教程：
回答by lakesh
Here is an example and tutorial: http://www.galloway.me.uk/tutorials/singleton-classes/
这是一个示例和教程：http: //www.galloway.me.uk/tutorials/singleton-classes/
Here is another one: How to create singleton class in objective C
这是另一个：如何在目标 C 中创建单例类
Singleton contains global variables and global functions.It's an extremely powerful way to share data between different parts of code without having to pass the data around manually.
Singleton 包含全局变量和全局函数。这是一种在代码的不同部分之间共享数据而无需手动传递数据的极其强大的方式。
