So, how you handle with SearchBar typing too fast?

情境就是 每輸入一個字母，就打一次api，有沒有辦法優化？

If you type too fast in search-bar API call errors out

1. 最直覺就是用UI擋XD
2. 記住搜尋過的結果

_____________________________以下是比較好的解法

3. 用Timer 做

利用 debounce 優化 search 時發送的 request

4. 用線成控制 DispatchWorkItem

什么是防抖和节流?

• debounce 應該是這個情境下比較好的解法 程式碼如下

struct DispatchSemaphoreWrapper {
    private var lock: DispatchSemaphore
    
    init(value: Int) {
        self.lock = DispatchSemaphore(value: value)
    }
    
    func sync(excute: () -> ()) {
        _ = lock.wait(timeout: DispatchTime.distantFuture)
        excute()
        lock.signal()
    }
}

class Debouncer {
    private let label: String
    private let interval: Int
    private let queue: DispatchQueue
    private var workItem: DispatchWorkItem?
    private var lock: DispatchSemaphoreWrapper

    /// interval: 毫秒
    init(label: String = "Debouncer", interval: Int = 500) {
        self.label = label
        self.interval = interval
        self.queue = DispatchQueue(label: label)
        self.lock = DispatchSemaphoreWrapper(value: 1)
    }

    func call(_ callback: @escaping (() -> ())) {
        self.lock.sync {
            self.workItem?.cancel()
            self.workItem = DispatchWorkItem {
                callback()
            }

            if let workItem = self.workItem {
                self.queue.asyncAfter(deadline: .now() + DispatchTimeInterval.milliseconds(interval), execute: workItem)
            }
        }
    }
}

new 一個

let d = Debouncer.init(interval: 2000)

然後call api 放到 callback

d.call {
  //your call
}

Fnish