Use case: incremental search

Debounce.swift

extension DispatchQueue {
    func debounce(delay: DispatchTimeInterval) -> (_ block: @escaping () -> Void) -> Void {
        var lastFireTime: DispatchTime = .now()
        
        return { [weak self, delay] block in
            let deadline: DispatchTime = .now() + delay
            lastFireTime = .now()
            
            self?.asyncAfter(deadline: deadline) { [delay] in
                let now: DispatchTime = .now()
                let when = lastFireTime + delay
                
                if now < when { return }
                lastFireTime = .now()
                block()
            }
        }
    }
}