我如何在then语句中返回承诺数组 [英] How can I return an array of promises in a then statement

问题描述

所以在过去的几个小时中，我一直在研究异步内容并使用诺言。我正在使用测试框架量角器，并且遇到了一些异步问题。

So for the past few hours I've been looking into async stuff and using promises. I'm using the testing framework protractor, and theres a few async things I'm having trouble with.

在此保存功能中，我异步调用cm.org1.all（），然后使用来获取响应。我遍历了响应，我需要对响应中的每个元素都调用getNewElement（），其中也有一个异步调用，因此每个元素都返回一个Promise。

In this save function, I call cm.org1.all() asynchronously, and use then to get the response. I loop over the response, and I need call getNewElement() to each element in the response, which also has an async call in it, so each returns a promise.

所以我有这一系列的承诺，但我不知道该如何兑现。 cm.save（）的返回值为[]。我需要将其设置为[‘foo’，foo’，foo’，foo’]

So I have this array of promises, but I don't know how to return it. The return of cm.save() is []. I need it to be ['foo',foo',foo',foo']

下面的代码不起作用，但这是我到目前为止的内容。

This code below doesn't work, but it's what I have so far.

 var cm = companyManagement() {
    //whatever is initialized below is initialized up here

    this.save = function() {
        cm.saveButton.click(); 
        var elements;
        var promises = [];
        var defer = protractor.promise.defer();
        cm.org1.all(by.repeater('brand in vm.brands'))
        .then(function(response) {
            //elements is of length 4
            elements = response;
            for(var i=0; i<elements.length;i++) {
                promises.push(getNewElement(elements, i));
            }
            //defer.fulfill(promises); not correct?
        });
        return protractor.promise.all(promises); //not correct?
    };

    function getNewElement(elements, i) {
         var defer = protractor.promise.defer();
        var alias = elements[i].element(by.binding('brand.alias'));
        alias.getText().then(function(aliasText) {
            defer.fulfill('foo');
        });
        return defer.promise;
    }
}
    cm.save()
    .then(function(response){
       console.log("my new array is",response);
    });

推荐答案

在测试中手动处理量角器承诺通常是问题过于复杂的迹象。 量角器具有涵盖大多数用例的各种抽象和功能编程工具。

Dealing with protractor promises manually in your tests is usually a sign of overcomplicating a problem. Protractor has a variety of abstractions and functional programming tools that cover most of the use cases.

您可以解决它如果您要使用中继器的 .column（） ：

You can solve it in just a single line if you would use repeater's .column():

this.save = function() {
    cm.saveButton.click(); 
    return cm.org1.all(by.repeater('brand in vm.brands').column('brand.alias')).getText();
};

---

---

我会做这样，但是如果列brand.alias与我拥有的某个常数匹配，我最终希望能够获得元素的父元素。如果我只有别名文本，而我无法获得父母的文本，如果我错了，请更正我。

I would do this, but I want to eventually be able to get the element's parent, if the column brand.alias matches with a certain constant I have. if I only have the alias text I couldn't be able to get the parent, correct me if I'm wrong.

< a href = http://angular.github.io/protractor/#/api?view=ElementArrayFinder.prototype.filter rel = nofollow> filter（） 和 map（） 进行救援：

filter() and map() to the rescue:

cm.org1.all(by.repeater('brand in vm.brands').column('brand.alias')).filter(alias) {
    return alias.getText().then(function (aliasText) {
        return aliasText === "foo";
    });
}).map(function (alias) {
    return alias.element(by.xpath("..")).getText();  // getting the parent
});

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