GCD function event handler for DispatchSource in Swift 3?

Question

In Objective-C, you could specify the event handler for a dispatch source as either a block or a function. From Apple's Concurrency Programming Guide:

Function-based event handlers take a single context pointer, containing the dispatch source object, and return no value. Block-based event handlers take no parameters and have no return value.

In Swift 3, is it still possible to use a function as an event handler? I only see how to use a block. I need access to the source in my handler and I need to define my handler separately from where the source is defined.

Mark Lilback · Accepted Answer · 2016-10-30 02:26:41Z

1

How about this?

class Foo {
    var eventHandler: (DispatchSourceRead) -> Void
    init(handler: @escaping (DispatchSourceRead) -> Void) {
        eventHandler = handler
    }
}

let foo = Foo() { source in
    print("got event from source")
}

let source = DispatchSource.makeReadSource(fileDescriptor: 0)
source.setEventHandler {
    foo.eventHandler(source)
}

answered Oct 30, 2016 at 2:26

Mark Lilback

1,1749 silver badges24 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

sam Over a year ago

You are using the block event handler, but you've written it so as to capture the source? Is that right? Could you have also done something like: let foo: (DispatchSourceRead) -> Void = { source in print("hi \(source)") } and then source.setEventHandler { foo(source) }? In other words, why do you need class Foo?

Mark Lilback Over a year ago

You don't need the class. That was my first thought as to why you needed it defined away from the source. To prevent the capture, you can add a capture list to the event handler that uses a weak reference to source.

Collectives™ on Stack Overflow

GCD function event handler for DispatchSource in Swift 3?

1 Answer 1

2 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

2 Comments

Your Answer

Sign up or log in

Post as a guest

Related