创建一个通用的单例 [英] Creating a generic singleton

问题描述

这是一个头部爆竹（对我来说）。基本上我想要从同一个类继承2个不同的单例。在任何一个我想使用本身派生的某个类。所以我有工具和 AUtil：工具和 BUtil：工具。并且 Singleton 用作 ASingleton 使用 AUtility 胃和 B 分别。我在各个方面都失败了。最后一次尝试是一个工厂模式，它将Swift 1.2简单地转换为Segfault：

$ p $协议可初始化{init（）}
类A：初始化{
var x =A
需要init（）{}
}
class B：可初始化{
var x =B
需要init（）{}
}

class C {
let t：可初始化
init（t：可初始化）{
self。 t = t
println（t）
}
func factory（）{
println（t.dynamicType（））
}
}

正如我所说的，我也尝试了以下模式：

  private let _SingletonSharedInstance = StaticClass（）
 $ b class class StaticClass {$ b $ class var sharedInstance：StaticClass {
 return _SingletonSharedInstance 
 } 
} 
 
 let s = StaticClass.sharedInstance 
  

（这不是你看到的通用，但我所有的尝试都失败了，所以我展示了我的出发点。）

无论如何，我似乎是在厄运和死亡之间迷失了方向。 ？

 协议可初始化：class {init（）} 
 
 private var instances = [String：Initializable ]（）
 
 func singletonInstance< T：Initializable>（_ ty：T.Type = T.self） - > T {
 let name = NSStringFromClass（ty）
 if let o =（instances [name] as？T）{
 return o 
} 
 let o = ty （）
 instances [name] = o 
 return o 
} 
  

<

  class Foo：Initializable {required init（）{}} 
 class Bar：Initializable {required init（）{}} 
 
 let foo1 = singletonInstance（）as Foo // or`singletonInstance（Foo.self）`
 let foo2 = singletonInstance（ ）作为Foo 
 assert（foo1 === foo2）
 
让bar1 = singletonInstance（）作为Bar 
让bar2 = singletonInstance（）作为Bar 
 assert（bar1 === bar2）
  

（我已经测试了上面的代码，并在Swift 1.2中使用它。）

This is a bit of a head banger (for me). Basically I want to have 2 different singletons that inherit from the same class. In either I want to use a certain class which itself is derived. So I have Utility and both AUtil:Utility and BUtil:Utility. And Singleton that is used as ASingleton using AUtility in its stomach and B respectively. I failed on all frontiers. The last attempt was a factory pattern which simply got Swift 1.2 to Segfault:

protocol Initializable { init() }
class A:Initializable {
  var x = "A"
  required init() {}
}
class B:Initializable {
  var x = "B"
  required init() {}
}

class C {
  let t:Initializable
  init(t:Initializable) {
    self.t = t
    println(t)
  }
  func factory() {
    println(t.dynamicType())
  }
}

As said I also tried to make the following pattern generic:

private let _SingletonSharedInstance = StaticClass()

class StaticClass {
  class var sharedInstance : StaticClass {
    return _SingletonSharedInstance
  }
}

let s = StaticClass.sharedInstance

(This one isn't generic as you see. But all my attempts failed and so I show my starting point.)

Anyway I seem to be lost between doom and death.

解决方案

Do you mean something like this?

protocol Initializable: class { init() }

private var instances = [String: Initializable]()

func singletonInstance<T: Initializable>(_ ty: T.Type = T.self) -> T {
    let name = NSStringFromClass(ty)
    if let o = (instances[name] as? T) {
        return o
    }
    let o = ty()
    instances[name] = o
    return o
}

An use-side of it, for instance.

class Foo: Initializable { required init() {} }
class Bar: Initializable { required init() {} }

let foo1 = singletonInstance() as Foo // or `singletonInstance(Foo.self)`
let foo2 = singletonInstance() as Foo
assert(foo1 === foo2)

let bar1 = singletonInstance() as Bar
let bar2 = singletonInstance() as Bar
assert(bar1 === bar2)

(I've tested the code above and got it to work in Swift 1.2.)

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