異步 - 類型錯誤：無法讀取屬性未定義

Question

「應用」我有這個簡單的代碼，這似乎與對齊async.waterfall應如何使用，但我有這個類型錯誤mentionned：

var myCallback = function (data){ 
    console.log("task done for " + data); 
} 

var test = function (param,callback) { 
    console.log("in test, doing some work, param is: " + param); 
    callback(param); 
}; 

async.waterfall([ 
    test("call 1",myCallback), 
    test("call 2",myCallback), 
    test("call 3",myCallback) 
], function (err, result) { 
    // result now equals 'done' 
}); 

結果的執行是：

in test, doing some work, param is: call 1 
task done for call 1 
in test, doing some work, param is: call 2 
task done for call 2 
in test, doing some work, param is: call 3 
task done for call 3 
/Users/.../Documents/.../node_modules/async/dist/async.js:5021 
      task.apply(null, args); 
       ^

TypeError: Cannot read property 'apply' of undefined 
    at nextTask (/.../node_modules/async/dist/async.js:5021:17) 
    at Object.waterfall (/.../node_modules/async/dist/async.js:5024:9) 
    at Object.<anonymous> (/.../app.js:77:7) 
    at Module._compile (module.js:409:26) 
    at Object.Module._extensions..js (module.js:416:10) 
    at Module.load (module.js:343:32) 
    at Function.Module._load (module.js:300:12) 
    at Function.Module.runMain (module.js:441:10) 
    at startup (node.js:139:18) 
    at node.js:968:3 

我一直在環顧四周，但找不到問題 - 一些幫助歡迎。非常感謝！ ç

Answer 1

試試下面的代碼：

async.waterfall([ 
    function(callback) { 
     task1().then(function(){ 
      callback(data) 
     }) 
    }, 
    function(data1, callback) { 
     task2().then(function(data2){ 
      callback(data1, data2) 
     }) 
    } 
], function(err, data1, data2) { 
    console.log('data'); 
}); 

您的代碼不工作，因爲它沒有當調用最終回調獲取並試圖調用一個不存在的另一個任務。