如何确保Dojo 1.10中两个Deferred的then回调均执行完成？

Hey there! Since you're using Dojo 1.10 with its built-in Deferred/Promise API, the perfect tool for this job is dojo/promise/all—it’s designed specifically to wait for multiple promises to finish before running a callback. Here's how to make it work for your scenario:

Key Background #

Every then() call on a Deferred returns a new Promise that resolves only when the then callback finishes executing (whether it returns a direct value or another promise). We need to wait for both of these derived promises to resolve before triggering completeFunc.

Step-by-Step Implementation #

First, import the dojo/promise/all module (it’s part of Dojo’s core promise utilities). Then wrap your two derived promises with all(), which creates a new promise that resolves only after both input promises are done.

Here’s your updated code:

// Import required Dojo modules
require(["dojo/promise/all", "dojo/Deferred"], function(all, Deferred) {
    var deferred_1 = new Deferred();
    // Capture the promise returned by deferred_1.then()
    var promise1 = deferred_1.then(function(value){
        // Your existing logic here
        return something;
    });

    var deferred_2 = new Deferred();
    // Capture the promise returned by deferred_2.then()
    var promise2 = deferred_2.then(function(value){
        // Your existing logic here
        return something;
    });

    var completeFunc = function(values){
        console.log("done");
        // Optional: Access results from each then callback
        // values[0] = return value from promise1, values[1] = return value from promise2
    };

    // Wait for both promises to resolve, then run completeFunc
    all([promise1, promise2]).then(completeFunc);

    // Don't forget to resolve your Deferreds somewhere in your code!
    // deferred_1.resolve(someTriggerValue);
    // deferred_2.resolve(anotherTriggerValue);
});

How It Works #

• dojo/promise/all takes an array of promises and returns a new aggregated promise.
• This aggregated promise only resolves after every promise in the input array has successfully resolved.
• When it resolves, it passes an array of results to completeFunc—the first element is the return value from promise1, the second from promise2.

Optional: Error Handling #

If either then callback or original Deferred might reject, add an error handler to catch failures:

all([promise1, promise2])
    .then(completeFunc)
    .catch(function(error) {
        console.error("One of the promises failed:", error);
    });

内容的提问来源于stack exchange，提问作者Joe