assign(to:on:)

Assigns each element from a publisher to a property on an object.

Declaration

func assign<Root>(to keyPath: ReferenceWritableKeyPath<Root, Self.Output>, on object: Root) -> AnyCancellable

Parameters

keyPath:
A key path that indicates the property to assign. See TP40014097 CH32 ID563 in The Swift Programming Language to learn how to use key paths to specify a property of an object.
object:
The object that contains the property. The subscriber assigns the object’s property every time it receives a new value.

Mentioned in

Return Value

An AnyCancellable instance. Call cancel() on this instance when you no longer want the publisher to automatically assign the property. Deinitializing this instance will also cancel automatic assignment.

Discussion

Use the assign(to:on:) subscriber when you want to set a given property each time a publisher produces a value.

In this example, the assign(to:on:) sets the value of the anInt property on an instance of MyClass:

class MyClass {
    var anInt: Int = 0 {
        didSet {
            print("anInt was set to: \(anInt)", terminator: "; ")
        }
    }
}

var myObject = MyClass()
let myRange = (0...2)
cancellable = myRange.publisher
    .assign(to: \.anInt, on: myObject)

// Prints: "anInt was set to: 0; anInt was set to: 1; anInt was set to: 2"