javascript - promise 在返回前不解决

Question

我很难弄清楚 promise 是如何工作的。我有以下代码，我正在执行遍历数组。

runOpts.automationResults.reduce(function (p, val) {
        return p.then(function () {
              return  pd.run(val);
});
}, Promise.resolve()).then(function (rallyResults) {
     console.log('returned from method');
     console.log('rallyResults ', rallyResults);
}, function (err) {
     console.log('error in reduce', err);
});

它正在调用下面的方法

ProcessDatabase.prototype.run = function (options) {
    return new Promise((resolve, reject) => {
        var dal = new db();
        var resultsArray = {
            results: [],
            options: [],
            testSet: [],
            testIteration: '',
            multipleSets: 0,
            totalCount: 0
        }
        resultsArray.options = options;
        dal.getAutomationResultsByBuild(options.Build).then((results) => {
            resultsArray.results = results;
            resultsArray.totalCount = results.data.length;
            resolve(resultsArray);
        })
    }).then(function (resultsArray) {
        var results = [];
        //console.log('resultsArray', resultsArray);
        //console.log(`Starting Rally publishing for Build '${resultsArray.options.Build}'...`)

        if (resultsArray.options.Executiontype == 'ci') {

            rallyApi.autoDiscoverTestSets().then((sets) => {
                resultsArray.testSet = sets.sets;
                resultsArray.testIteration = sets.iteration;
                resultsArray.multipleSets = sets.sets.length > 1;
                results.push(resultsArray);
                console.log('results', results);
            }, (err) => { reject(err); });
            // totalResults = totalResults + results.data.length;
        } else {
            rallyApi.addTestSet('Automation: ' + resultsArray.options.type + ' - ' + resultsArray.options.build, config.get('rally.projects.testing.ref'), null, resultsArray.options.SessionUser).then((resp) => {
                //console.log(resp);
                console.log('New test set ' + resp.FormattedID + ' created.');
                resultsArray.multipleSets = 0;
                resultsArray.testSet = resp.FormattedID;
                //console.log('resultsArray', resultsArray);
                results.push(resultsArray);
                console.log('results', results);
            }, (err) => {
                console.log(err);
            });
        }

        console.log('results', results);
        return Promise.all(results);

    })
}

我已经尝试了我目前所拥有的几个不同的迭代，它总是在 ProcessDatabase.prototype.run 方法中的结果完成之前返回到调用 .reduce。

我已经输入了控制台日志，这就是我得到的。我可以看到最终结果数组包含我需要的所有信息。我只是无法弄清楚如何将其传递回调用 .reduce。

---These are actually from the .reduce and are written to the log before the results in the method called
returned from method 
rallyResults  [] 

**----These are from the ProcessDatabase.prototype.run method called**
**This is the contents of the "results" set the first iteration through**
-- Found 2 test sets.
results [ { results: { _success: true, _message: '', _data: [Array] },
    options:
     { Executiontype: 'ci',
       Build: 'test_030518_103956',
       Environment: 'dev',
       SessionUser: 'https://rally1.rallydev.com/slm/webservice/v2.0/user/165547093296' },
    testSet: [ [Object], [Object] ],
    testIteration: 'https://rally1.rallydev.com/slm/webservice/v2.0/iteration/184203152680',
    multipleSets: true,
    totalCount: 4 } ]
New test set TS2969 created.

**This is the contents of the "result" set after the second iteration 
through and what I trying to get passed back to the calling .reduce.**

results [ { results: { _success: true, _message: '', _data: [Array] },
    options:
     { Executiontype: 'ci',
       Build: 'test_030518_103956',
       Environment: 'dev',
       SessionUser: 'https://rally1.rallydev.com/slm/webservice/v2.0/user/165547093296' },
    testSet: [ [Object], [Object] ],
    testIteration: 'https://rally1.rallydev.com/slm/webservice/v2.0/iteration/184203152680',
    multipleSets: true,
    totalCount: 4 },
  { results: { _success: true, _message: '', _data: [Array] },
    options:
     { Executiontype: 'regression',
       Build: 'test_030518_110447',
       Environment: 'dev',
       SessionUser: 'https://rally1.rallydev.com/slm/webservice/v2.0/user/165547093296' },
    testSet: 'TS2969',
    testIteration: '',
    multipleSets: 0,
    totalCount: 6 } ]
    

如有任何帮助，我们将不胜感激。谢谢克里斯汀

Answer 1

此代码中存在许多问题，但主要问题是当您在 .then() 处理程序中运行另一个异步操作时，您必须从 返回该 promise >.then() 以将其正确链接到主 promise 链中。如果您不这样做，那么父级 promise 根本不会与该内部 promise 相关联(它成为自己独立的 promise 链，您无法监控它)并且父级 promise 不会等待内部 promise 。

以下是所做的更改:

1. 移除在另一个 promise 中不必要地包装一个 promise 的 promise 反模式(只返回你已经拥有的 promise)
2. 从 .then() 处理程序中返回嵌套的 promise 以适本地链接它们
3. 将错误记录合并到一个地方并重新抛出错误，以便正确返回
4. 删除 Promise.all()。
5. 删除 results.push(resultsArray); 因为这似乎没有任何意义。按照我在下面编写代码的方式，顶级 promise 解析为 resultsArray，因为只有其中一个，所以我认为没有必要将它嵌入另一个数组。

修改后的代码:

ProcessDatabase.prototype.run = function (options) {
    var dal = new db();
    var resultsArray = {
        results: [],
        options: {},
        testSet: [],
        testIteration: '',
        multipleSets: 0,
        totalCount: 0
    }
    resultsArray.options = options;
    return dal.getAutomationResultsByBuild(options.Build).then((results) => {
        resultsArray.results = results;
        resultsArray.totalCount = results.data.length;
        return resultsArray;
    }).then(function (resultsArray) {
        //console.log('resultsArray', resultsArray);
        //console.log(`Starting Rally publishing for Build '${resultsArray.options.Build}'...`)

        if (resultsArray.options.Executiontype == 'ci') {

            return rallyApi.autoDiscoverTestSets().then((sets) => {
                resultsArray.testSet = sets.sets;
                resultsArray.testIteration = sets.iteration;
                resultsArray.multipleSets = sets.sets.length > 1;
                return resultsArray;
            });
        } else {
            return rallyApi.addTestSet('Automation: ' + resultsArray.options.type + ' - ' + resultsArray.options.build, config.get('rally.projects.testing.ref'), null, resultsArray.options.SessionUser).then((resp) => {
                //console.log(resp);
                console.log('New test set ' + resp.FormattedID + ' created.');
                resultsArray.multipleSets = 0;
                resultsArray.testSet = resp.FormattedID;
                return resultsArray;
            });
        }

    }).catch(err => {
        // log error and rethrow
        console.log(err);
        throw err;
    });
}