鏈接多個異步功能

Question

介紹

我有一個問題來自這一個來：

Loop calling an asynchronous function

一旦我得到了一個循環調用使用承諾狀圖案異步函數（jsdeferred使用SDK開發的附加組件庫）。

var sess = ...; 
Deferred.define(this);  
function asyncFunction (session) { 
    Deferred.next(function() { 
     var d = new Deferred(); 
     (new Request({ 
       url: form.php, 
       content: "sess=" + session, 
       onComplete: function (response) { 
        d.call(response.json); 
       } 
     })).get(); 
     return d; 
    }).next(function(resp) { 
     if (resp.id) { 
      asyncFunction(session); 
      console.log(resp.msg);    
     }   
    }); 
} 

asyncFunction(sess); 

我想鏈新asynchrnous功能到這個請求，例如，打開瀏覽器的標籤：我不想繼續執行，直到已準備就緒。

問題

所以我得到這樣的：

var sess = ...; 
Deferred.define(this);  
function asyncFunction (session) { 
    Deferred.next(function() { 
     var d = new Deferred(); 
     (new Request({ 
       url: form.php, 
       content: "sess=" + session, 
       onComplete: function (response) { 
        d.call(response.json); 
       } 
     })).get(); 
     return d; 
    }) 
    .next(function(resp) { 
     var d = new Deferred(); 
     // Load tab 
     tabs.activeTab.url = 'http://foo.com'; 
     tabs.activeTab.on('ready', function() { 
      console.log(resp.id); 
      d.call(resp.id); 
     }); 
     return d; 
    }) 
    .next(function(resp) { 
     if (resp.id) { 
      asyncFunction(session); 
      console.log(resp.msg);    
     }   
    }); 
} 

asyncFunction(sess); 

而我得到的是，對於循環的每個迭代，它再次運行所有先前請求的結果！所以，我得到了下面的日誌中我的控制檯：

id1 
msg1 
id1 
msg1 
id2 
msg2 
id1 
msg1 
id2 
msg2 
id3 
msg3 
... 

顯然，我的預期是：

id1 
msg1 
id2 
msg2 
id3 
msg3 

問題

很清澈，我不明白的承諾的模式。我在兩個API讀了很多：

• jsdeferred
• FF add-on sdk

首先是我一直使用到現在爲止的一個。當我嘗試要求庫中的第二個給出了一個錯誤：

const { defer } = require('api-utils/promise'); (+) 

所以，我的問題是，如果你知道承諾的任何好的教程或一些很好的例子約鏈接多個異步函數。或者如果你知道如何去做，你會怎麼做。

謝謝

編輯：給予行（+）

error: An exception occurred. 
Traceback (most recent call last): 
    File "resource://ares-at-iiia-dot-csic/api-utils/lib/promise.js", line 16, in 
    }.call(this, function(require, exports) { 
    File "resource://ares-at-iiia-dot-csic/api-utils/lib/promise.js", line 6, in return  function promised 
    if (typeof(define) === 'function') { // RequireJS 
    File "function promisedConcat(promises, unknown) {return promises.then(function   (values) {return resolve(unknown).then(function (valu 
e) {return values.concat(value);});});", line NaN, in function promisedConcat 
    File "function execute(args) {return call.apply(call, args);", line NaN, in function  execute 
    File "exports.reject = reject;var promised = function() {var call =  Function.call;var concat = Array.prototype.concat", line NaN, in 
exports.reject = reject;var promised = function 
    File "function reject(reason, prototype) {var deferred =   defer(prototype);deferred.reject(reason);return deferred.promise;", line NaN 
, in function reject 
    File "exports.resolve = resolve", line NaN, in exports.resolve = resolve 
    File "function resolve(value, prototype) {var deferred =  defer(prototype);deferred.resolve(value);return deferred.promise;", line NaN 
, in function resolve 
    File "exports.defer = defer", line NaN, in exports.defer = defer 
    File "if (pending) {pending.push([resolved, rejected]);} else {result.then(resolved,  rejected);}return deferred.promise;}}});var defe 
rred = {promise: promise, resolve: function resolve(value) {if (pending) {result =  isPromise(value) ? value : resolution(value);while (
pending.length) {result.then.apply(result, pending.shift());}pending = null;}},  reject", line NaN, in if 
    File "function rejected(reason) {deferred.resolve(reject(reason));", line NaN, in  function rejected 
    File "function resolved(value) {deferred.resolve(resolve(value));", line NaN, in  function resolved 
    File "function defer(prototype) {var pending = [], result;prototype = prototype ||  prototype === null ? prototype : Object.prototype; 
var promise = Object.create(prototype, {then: {value: function then(resolve, reject)  {var deferred = defer(prototype);resolve = resolve 
? attempt(resolve) : resolution;reject = reject ? attempt(reject) ", line NaN, in  function defer 
    File "function isPromise(value) {return value && typeof value.then === "function";",  line NaN, in function isPromise 
    File "function attempt(f) {return function effort(options) {try {return f(options);}  catch (error) {return rejection(error);}};", lin 
e NaN, in function attempt 
    File "function rejection(reason) {return {then", line NaN, in function rejection 
    File "function resolution(value) {return {then", line NaN, in function resolution 
    File "((function (require, exports) {"use strict"", line NaN, in 
    File "resource://ares-at-iiia-dot-csic/api-utils/lib/globals!.js", line 75, in getter 
    value: define.bind(this) 
TypeError: can't redefine non-configurable property 'define' 

Answer 1

嗯，看起來有點像一個範圍問題的錯誤。在你的最後一個函數中，應該沒有可用的變量resp - 我不確定它的真實記錄。

是的，因爲你最後再次調用asyncFunction，只要響應中有一個id，你可能會得到一個無限循環。

但是，讓我們嘗試使用add-on sdk's promises（不，我從來沒有使用過 - 但它說，它是基於CommonJS Promises/A）：

const { defer } = require('api-utils/promise'); 
// or whatever you need in your code to use them - I'm no addOn-developer 

var sess = ...; 
Deferred.define(this);  
function asyncFunction (session) { 
/* returns a promise itself */ 

    var d = defer(); 
    (new Request({ 
     url: form.php, 
     content: "sess=" + session, 
     onComplete: function (response) { 
      d.resolve(response.json); 
     } 
    })).get(); 
    return d.promise.then(function(resp) { 
     var d = defer(); 
     // Load tab 
     tabs.activeTab.url = 'http://foo.com'; 
     tabs.activeTab.on('ready', function() { 
      d.resolve(resp); 
     }); 
     return d.promise; 
    }).then(function(resp) { 
     console.log("request #"+resp.id+"sucessful: "+resp.msg); 
     if (resp.id) { 
      asyncFunction(session); // call recursively 
     }   
    }); 
} 
asyncFunction(sess);