通过fsharp 使用Enterprise Library Unity

<span style="font-family: Arial, Helvetica, sans-serif; background-color: rgb(255, 255, 255);">使用Ioc概念的Unity库的优点,简单的说就是进一步解耦系统各组件的依赖关系。客户端代码只需依赖需要使用的接口（服务）就可以快速的进行开发。</span>

1.基本流程，定义类-->配置container-->解析类，并使用-->析构（依策略）
2.注册的类型
注册实例，类似单件模式
注册类型，各种扩展
    构造函数类
        1.注册时InjectionConstructor声明类型，之前没有经过注册，无法解析；会在生成对象时产生错误。（可以在解析过程时化解）

let container = new UnityContainer()

type TenantStore() = 
    interface ITenantStore with
        member this.Msg() = printfn "Hello, it's TenantStore"
    interface IDisposable with
        member this.Dispose() = printfn "TenantStore hase been cleaned"

type ManagementController(st:ITenantStore, _name:string) =
    member this.TStore = st
    member val Name = _name with get, set
    interface IDisposable with
        member this.Dispose() = printfn "Control %A hase been cleaned" this.Name

using(new TenantStore())(fun x -> 
    (x:>ITenantStore).Msg())

container.RegisterType<ITenantStore, TenantStore>()
container.RegisterType<ManagementController>(new InjectionConstructor(typeof<ITenantStore>, typeof<string>))

using(container.Resolve<ManagementController>(new ParameterOverride("_name", (box "hello"))))(fun myctrl ->
    printfn "%A" myctrl.TStore)

        2.函数中的参数可以在解析过程中（Resolve的过程中）重载。
        3.泛型类注册，以参数形式表明注册类，可以在注册时忽略泛型类型，在解析时指定
    使用typeof获得类型时会默认用obj替换泛型类，无法产生延时定义的效果。需要改用typedefof来获取带泛型的类型
    [参考]http://stackoverflow.com/questions/6783284/how-to-get-generic-type-definition-for-crtp-type

type IMessage<'a> = 
    abstract member Send : 'a -> unit


type Message<'a>() = 
    interface IMessage<'a> with
        member this.Send(msg:'a) = 
            printfn "Send Message %A" msg

//Not work
//container.RegisterType(typeof<IMessage<_>>, typeof<Message<_>>)
container.RegisterType(typedefof<IMessage<_>>, typedefof<Message<_>>)

//观察注册类
container.Registrations |> Seq.iter (fun i -> printfn "Regist Type:%A" i.RegisteredType)

let y = container.Resolve<IMessage<int>>()                                              
y.Send(413)                                     

let z = container.Resolve<IMessage<bool>>()                                              
z.Send(true)     <span style="font-family: Arial, Helvetica, sans-serif; background-color: rgb(255, 255, 255);">         </span>

4.属性注入
Fsharp的属性无法直接设为Null值，所以在进行属性注入的过程中需要用到一些技巧
如果是轻量级的对象可以默认给个对象实例做填充物，不过这肯定不是个好办法。

type MyClass() as x= 
    let t = new TenantStore() :> ITenantStore
    [<Dependency>]
    member val PProperty: ITenantStore = t with get, set

附加一个null field做填充物。这个实现最接近c#，不过接口多了的话，未整理的零零碎碎的小东西怎么也是桩心事。

type MyClass() as x= 
    [<DefaultValue>]
    val mutable t:ITenantStore
    [<Dependency>]
    member val PProperty: ITenantStore = x.t with get, set

其实null不是个好东西，异常之源！fsharp为了摆脱null给出了option的解决方案，这里能用么？我试了一下

type MyClass() as x= 
    [<Dependency>]
    member val PProperty: ITenantStore option = None with get, set

结果还真行！漂亮多了不是么？而且绝对没有null的参与。我觉得面向对象的哲学里，所有的对象都应该有一个确定的身份。null只是一个系统遗留产物，少用为好。不过这里也有个缺点。获得PProperty时需要获得背后的值，多了一步。

五种声明周期探索
默认为
0.短时生命周期（Transient LifeTime）
生成不一样的对象

container.RegisterType<ITenantStore, TenantStore>()

let a = container.Resolve<ITenantStore>()
let b = container.Resolve<ITenantStore>()
printfn "Is a eqaul to b: %A" (a.Equals(b))

</pre>false1.容器生命周期（Container LifetimeManger）近似于单件模式<pre name="code" class="plain">container.RegisterType<ITenantStore, TenantStore>(new ContainerControlledLifetimeManager())

let a = container.Resolve<ITenantStore>()
let b = container.Resolve<ITenantStore>()
printfn "Is a eqaul to b: %A" (a.Equals(b))

true
2.层次生命周期（Hierarchical Life Time）
脑补一个树形图

container.RegisterType<ITenantStore, TenantStore>(new HierarchicalLifetimeManager())
let childcontainer = container.CreateChildContainer()

let a = container.Resolve<ITenantStore>()
let b = childcontainer.Resolve<ITenantStore>()
printfn "Is a eqaul to b: %A" (a.Equals(b))

false
3单独解生命周期（PreResolve Life Time）
理解为当多个不同类依赖于同一个类时（资源类），获取该对象时并不会重复解析该类。
一定要为三层以上的对象结构，单层产生不了这样的效果

type ITenantStore = 
    abstract member Msg : unit->unit

type TenantStore() as x= 
    do printfn "new TenantStore %A" (x.GetHashCode())
    interface ITenantStore with
        member this.Msg() = printfn "Hello, it's TenantStore"

type ManagementController(st:ITenantStore, _name:string) =
    member this.TStore = st
    member val Name = _name with get, set
    interface IDisposable with
        member this.Dispose() = printfn "Control %A hase been cleaned" this.Name

type ExManagementController(st:ITenantStore, _name:string) =
    member this.TStore = st
    member val Name = _name with get, set
    interface IDisposable with
        member this.Dispose() = printfn "Control %A hase been cleaned" this.Name

type CombineManagement(m1:ManagementController, m2:ExManagementController) = 
    member this.M1 = m1
    member this.M2 = m2

//注册
container.RegisterType<ITenantStore, TenantStore>(new PerResolveLifetimeManager())
container.RegisterType<ManagementController>(new InjectionConstructor(typeof<ITenantStore>, "xx"))
container.RegisterType<ExManagementController>(new InjectionConstructor(typeof<ITenantStore>, "yy"))
container.RegisterType<CombineManagement>()

//获取
let o = container.Resolve<CombineManagement>()
printfn "%d,%d" (o.M1.TStore.GetHashCode()) (o.M2.TStore.GetHashCode())

还有线程相关，网络相关，外部控制的生命周期，暂未深究