Događaj
Izgradite inteligentne aplikacije
17. mar 23 - 21. mar 23
Pridružite se seriji sastanaka kako biste izgradili skalabilna AI rešenja zasnovana na stvarnim slučajevima korišćenja sa kolegama programerima i stručnjacima.
Registrujte se odmahOvaj pregledač više nije podržan.
Nadogradite na Microsoft Edge biste iskoristili najnovije funkcije, bezbednosne ispravke i tehničku podršku.
An object expression is an expression that creates a new instance of a compiler generated, anonymous object type that is based on an existing base type, interface, or set of interfaces.
// When typename is a class:
{ new typename [type-params]arguments with
member-definitions
[ additional-interface-definitions ]
}
// When typename is not a class:
{ new typename [generic-type-args] with
member-definitions
[ additional-interface-definitions ]
}
In the previous syntax, the typename represents an existing class type or interface type. type-params describes the optional generic type parameters. The arguments are used only for class types, which require constructor parameters. The member-definitions are overrides of base class methods, or implementations of abstract methods from either a base class or an interface.
The following example illustrates several different types of object expressions.
// This object expression specifies a System.Object but overrides the
// ToString method.
let obj1 = { new System.Object() with member x.ToString() = "F#" }
printfn $"{obj1}"
// This object expression implements the IFormattable interface.
let delimiter(delim1: string, delim2: string, value: string) =
{ new System.IFormattable with
member x.ToString(format: string, provider: System.IFormatProvider) =
if format = "D" then
delim1 + value + delim2
else
value }
let obj2 = delimiter("{","}", "Bananas!");
printfn "%A" (System.String.Format("{0:D}", obj2))
// Define two interfaces
type IFirst =
abstract F : unit -> unit
abstract G : unit -> unit
type ISecond =
inherit IFirst
abstract H : unit -> unit
abstract J : unit -> unit
// This object expression implements both interfaces.
let implementer() =
{ new ISecond with
member this.H() = ()
member this.J() = ()
interface IFirst with
member this.F() = ()
member this.G() = () }
You use object expressions when you want to avoid the extra code and overhead that is required to create a new, named type. If you use object expressions to minimize the number of types created in a program, you can reduce the number of lines of code and prevent the unnecessary proliferation of types. Instead of creating many types just to handle specific situations, you can use an object expression that customizes an existing type or provides an appropriate implementation of an interface for the specific case at hand.
Povratne informacije za .NET
.NET je projekat otvorenog koda. Izaberite vezu da biste pružili povratne informacije:
Događaj
Izgradite inteligentne aplikacije
17. mar 23 - 21. mar 23
Pridružite se seriji sastanaka kako biste izgradili skalabilna AI rešenja zasnovana na stvarnim slučajevima korišćenja sa kolegama programerima i stručnjacima.
Registrujte se odmah