clojurescript中core.async的優點是什麼？

Question

大家都在談論core.async的優點，以及它如何改進clojurescript中的事件處理。我一直在關注ClojureScript 101教程，而我從這些代碼示例中看不到任何明顯的優勢。我錯過了什麼？

爲什麼在這裏使用core.async更好？

(defn listen [el type] 
    (let [out (chan)] 
    (events/listen el type 
     (fn [e] (put! out e))) 
    out)) 

(defn dosomethingasync 
    [e] 
    (js/console.log "async: " e)) 

(let [clicks (listen (dom/getElement "search1") "click")] 
    (go (while true (dosomethingasync (<! clicks))))) 

與

(defn dosomethingcallback 
    [e] 
    (js/console.log "callback: " e)) 

(events/listen (dom/getElement "search2") "click" dosomethingcallback) 

Answer 1

大問題！

我想你的第一個步驟，瞭解好處是Timothy Baldridge Video

而且我下面的嘗試：

我認爲差異將清理，如果我們改了一下你的代碼。

首先，刻意突出了一句「總會有一個在所有的好節目的時候，組件或子系統必須停止直接相互通信」從core.async的貼在clojure blog呈現提取。我認爲，我們可以輸入事件通道從設FN分開：

(def clicks (listen (dom/getElement "search1") "click")) 

(go 
    (while true 
    (dosomethingasync (<! clicks)))) 

(put! clicks "this channel can be written from differents parts of your code") 

其次，core.async我們可以寫爲我們寫同步調用（順序代碼）異步調用。這種情況的一個例子需要一個以上的頻道：

(def clicks (listen (dom/getElement "search1") "click")) 

(def keys-pressed (listen (dom/getElement "search1") "keypress")) 

(def to-out (chan)) 

(go 
    (while true 
    (let [click-recieved (<! clicks)] 
     (dosomethingasync click-recieved) 
     (>! to-out "click recieved!") 
     (let [other-input-waited (<! keys-pressed)] 
     (dosomethingwithkey other-input-waited) 
     (>! to-out "keypressed recieved!") 
     ) 
    ) 
    )) 

最後，我認爲你沒有正確使用回調函數的含義。當我們討論一個回調函數時，我認爲我們所指的是一個函數，除了它自己的參數之外，它還會接收一個函數「callback」。在函數執行結束時，我們調用回調函數將執行流程返回到原始點。 改變你的「回調」功能上來如下：

(defn dosomethingcallback 
    [e call-back-fn] 
    (js/console.log "callback: " e) 
    (call-back-fn)) 

如果我們試圖發出類似於前面的代碼core.async例如實現相同的行爲的內容：

(defn do-key 
    [call-back-fn e] 
    (.log js/console "before callback key") 
    (call-back-fn e)) 

(defn do-click 
    [call-back-fn e] 
    (.log js/console "before callback click") 
    (call-back-fn e)) 

(defn key-callback-fn [e] 
    (.log js/console (str "doing some work with this key: " e)) 
) 

(defn click-callback-fn [e] 
    (.log js/console (str "doing some work with this click" e)) 
    (events/listen (dom/getElement "search2") "keypress" (partial do-key key-callback-fn))) 


    (events/listen (dom/getElement "search2") "click" (partial do-click click-callback-fn))