1

介绍

我有一个问题来自这个：

循环调用异步函数

一旦我得到一个使用类似承诺的模式（使用 SDK 开发的附加组件中的 jsdeferred 库）调用异步函数的循环。

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);

我想将一个新的异步函数链接到这个请求中，例如，打开浏览器的选项卡：我不想在准备好之前继续执行。

问题

所以我明白了：

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);

我得到的结果是，对于循环的每次迭代，它都会再次运行所有先前的请求！所以我在控制台中得到了以下日志：

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

显然我的预期是：

id1
msg1
id2
msg2
id3
msg3

问题

很明显，我不理解承诺模式。我在两个 API 中阅读了很多内容：

第一个是我一直使用到现在的那个。当我尝试要求该库时，第二个给出错误：

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

所以，我的问题是你是否知道任何关于承诺的好教程或一些关于链接多个异步函数的好例子。或者如果你知道怎么做，你会怎么做。

谢谢

编辑：给出行（+）的错误

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'
4

1 回答 1

2

嗯，看起来有点像范围界定问题。在您的最后一个函数中，应该没有resp可用的变量 - 我不确定它真正记录了什么。

是的，因为你asyncFunction最后再次调用，只要响应中有一个 id，你可能会得到一个无限循环。

但是，让我们尝试使用附加 sdk 的承诺（不，我以前从未使用过它们 - 但它说它是基于CommonJS Promises/A 的）：

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);
于 2012-07-12T11:59:35.403 回答