I found this in the Mozilla Firefox for iOS repository.
static let WebServerSharedInstance = WebServer()
class var sharedInstance: WebServer {
return WebServerSharedInstance
}
Why would you create a new variable that just returns the same variable when you could do the same in one line like this?
static let sharedInstance = WebServer()
I have looked into the code and I think I have misunderstood the context:
class WebServer {
static let WebServerSharedInstance = WebServer()
class var sharedInstance: WebServer {
return WebServerSharedInstance
}
}
While you can always use WebServer.WebServerSharedInstance to access the singleton, a subclass of WebServer can override sharedInstance.
class MyServer : WebServer {
override class var sharedInstance: MyServer {
return MyServer()
}
}
However, I have found no example in the code doing that so the original answer below is probably correct.
Original answer:
You are right. There is absolutely no reason to do that.
This has been probably translated directly from Objective-C, which uses similar syntax for singletons.
Also, with Swift 1.0 we weren't very sure how to create singletons and whether static let on a class is Thread safe.
I'm not sure the context. But let me explain one of the key differences between
// 1
class var sharedInstance: WebServer {
return WebServerSharedInstance
}
vs
// 2
static let sharedInstance = WebServer()
1 is computed variable which gets evaluated each time you access, while 2 get initialized lazily and evaluated only once.
If later in your code someone reassigns the WebServerSharedInstance
The 1 will return the new value while 2 will keep returning the initial value if it got initialized before.
You can simplify the declaration of a read-only computed property by removing the get keyword and its bracesA suggestion is that WebServerSharedInstance is a global variable declared at the top level of the file which lives as long as the file lives which is as long as the program runs --> You can use that variable in all other files
WebServerSharedInstance a global variable?