How can I debounce a method call?

Question

I\'m trying to use a UISearchView to query google places. In doing so, on text change calls for my UISearchBar, I\'m making a request to google pla

Answer 1

owenoak's solution works for me. I changed it a little bit to fit my project:

I created a swift file Dispatcher.swift:

import Cocoa

// Encapsulate an action so that we can use it with NSTimer.
class Handler {

    let action: ()->()

    init(_ action: ()->()) {
        self.action = action
    }

    @objc func handle() {
        action()
    }

}

// Creates and returns a new debounced version of the passed function 
// which will postpone its execution until after delay seconds have elapsed 
// since the last time it was invoked.
func debounce(delay: NSTimeInterval, action: ()->()) -> ()->() {
    let handler = Handler(action)
    var timer: NSTimer?
    return {
        if let timer = timer {
            timer.invalidate() // if calling again, invalidate the last timer
        }
        timer = NSTimer(timeInterval: delay, target: handler, selector: "handle", userInfo: nil, repeats: false)
        NSRunLoop.currentRunLoop().addTimer(timer!, forMode: NSDefaultRunLoopMode)
        NSRunLoop.currentRunLoop().addTimer(timer!, forMode: NSEventTrackingRunLoopMode)
    }
}

Then I added the following in my UI class:

class func changed() {
        print("changed")
    }
let debouncedChanged = debounce(0.5, action: MainWindowController.changed)

The key difference from owenoak's anwer is this line:

NSRunLoop.currentRunLoop().addTimer(timer!, forMode: NSEventTrackingRunLoopMode)

Without this line, the timer never triggers if the UI loses focus.