如何使用 angularjs $q 依次链接 promise? [英] How do I sequentially chain promises with angularjs $q?

问题描述

在promise库Q中，您可以执行以下操作来顺序链接promise:

In the promise library Q, you can do the following to sequentially chain promises:

var items = ['one', 'two', 'three'];
var chain = Q();
items.forEach(function (el) {
  chain = chain.then(foo(el));
});
return chain;

但是，以下内容不适用于 $q:

however, the following doesn't work with $q:

var items = ['one', 'two', 'three'];
var chain = $q();
items.forEach(function (el) {
  chain = chain.then(foo(el));
});
return chain;

推荐答案

只需使用 $q.when() 函数:

Simply use the $q.when() function:

var items = ['one', 'two', 'three'];
var chain = $q.when();
items.forEach(function (el) {
  chain = chain.then(foo(el));
});
return chain;

注意:foo 必须是工厂，例如

Note: foo must be a factory, e.g.

function setTimeoutPromise(ms) {
  var defer = $q.defer();
  setTimeout(defer.resolve, ms);
  return defer.promise;
}

function foo(item, ms) {
  return function() {
    return setTimeoutPromise(ms).then(function () {
      console.log(item);
    });
  };
}

var items = ['one', 'two', 'three'];
var chain = $q.when();
items.forEach(function (el, i) {
  chain = chain.then(foo(el, (items.length - i)*1000));
});
return chain;

这篇关于如何使用 angularjs $q 依次链接 promise?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！