apparently the following is not available in swift anymore:
[self performSelector:@selector(onFlip) withObject:nil afterDelay:0.3];
why is this the case if the following is still present:
NSObject.cancelPreviousPerformRequestsWithTarget(self, selector: singleTapSelector, object: nil)
doesn't nsobject.cancel work with performSelector? why have the cancel functionality but not the perform functionality?
Use
NSTimer.scheduledTimerWithTimeInterval(delay, target: self, selector: "onFlip", userInfo: nil, repeats: false)
instead. No idea why the other one is not available.
These methods from the perfromSelector family actually exist in Swift but they were artificially hidden (by design, I think) prior Swift 2.0. They can be unveiled using swizzling and some Objective-C runtime hacks right in Swift.
Just add this extension file NSObject+PerformSelector.swift and prefix all calls with symbol.
In your case the code:
[self performSelector:@selector(onFlip) withObject:nil afterDelay:0.3];
can be rewritten in Swift like this:
self.performSelector("onFlip", withObject: nil, afterDelay: 0.3)
With using this magical category (class extension):
NSObject+PerformSelector.swift
import Foundation
private var dispatchOnceToken: dispatch_once_t = 0
private var selectors: [Selector] = [
"performSelector:",
"performSelector:withObject:",
"performSelector:withObject:withObject:",
"performSelector:withObject:afterDelay:inModes:",
"performSelector:withObject:afterDelay:",
]
private func swizzle() {
dispatch_once(&dispatchOnceToken) {
for selector: Selector in selectors {
let selector = Selector("\(selector)")
let method = class_getInstanceMethod(NSObject.self, selector)
class_replaceMethod(
NSObject.self,
selector,
method_getImplementation(method),
method_getTypeEncoding(method)
)
}
}
}
extension NSObject {
func performSelector(selector: Selector) -> AnyObject? {
swizzle()
return self.performSelector(selector)
}
func performSelector(selector: Selector, withObject object: AnyObject?) -> AnyObject? {
swizzle()
return self.performSelector(selector, withObject: object)
}
func performSelector(selector: Selector, withObject object1: AnyObject?, withObject object2: AnyObject?) -> AnyObject? {
swizzle()
return self.performSelector(selector, withObject: object1, withObject: object2)
}
func performSelector(selector: Selector, withObject object: AnyObject?, afterDelay delay: NSTimeInterval, inModes modes: [AnyObject?]?) {
swizzle()
self.performSelector(selector, withObject: object, afterDelay: delay, inModes: modes)
}
func performSelector(selector: Selector, withObject object: AnyObject?, afterDelay delay: NSTimeInterval) {
swizzle()
self.performSelector(selector, withObject: object, afterDelay: delay)
}
}
func performFlipOnDelay() {
let delayInSeconds = 1.0
let delay = dispatch_time(DISPATCH_TIME_NOW, Int64(delayInSeconds * Double(NSEC_PER_SEC)))
dispatch_after(delay, dispatch_get_main_queue()) {
onFlip();
}
}
Another round about answer would be the above using GCD to add a delay time for an action to be performed
Taking the answer from Thomas Kilian a step further, primarily to enhance readability on calling clients, I've defined a swift utility, TimerUtil.swift, defining a facade on NSTimer for this particular usecase:
import Foundation
/**
* Convenience function to make a single timer scheduling more readable.
*/
public func invoke( selector:Selector, on target:AnyObject, afterDelay delay:NSTimeInterval ) {
NSTimer.scheduledTimerWithTimeInterval( delay, target: target, selector: selector, userInfo: nil, repeats: false )
}
Then your code can simply call:
invoke( "onFlip", on:self, afterDelay:0.3 )
which more or less resembles performSelector:withObject:afterDelay
In Swift 4 use This to Handle These Types of Warning!
perform(#selector(yourMethodName), with: nil, afterDelay: 0, inModes: [])
