Question

我无法使用promises控制我的方法流程：

//FIND CHECKED OUT FILES
getCheckedOutFiles = function () {
    console.log('Get checked out files');
    var d = $q.defer();

    // Store final results and pass to then callback
    var checkedOutFiles = window.x = [];

    // Promise, returns collection with all sites 
    SiteService.getAllSites()
        .then(sites => {
            // For each site get lists then get items matching filter
            sites.forEach(function (site) {
                var web = new $pnp.Web(site.url);

                return web.lists
                    .filter("BaseTemplate eq 101")
                    .get() // Returns promise with all lists matching filter 
                    .then(lists => {
                        // Go through each list and find matching item 
                        lists.forEach(function (list) {
                            web.lists.getByTitle(list.Title).items
                                .filter("CheckoutUser ne null")
                                .expand("File, File/Author, File/ModifiedBy, File/CheckedOutByUser")
                                .get() // Returns promise with all items matching filter 
                                .then(files => {
                                    // Loop through each item, get properties, add to collection 
                                    files.forEach(function (f) {
                                        var fileObject = {
                                            fileName: f.File.Name,
                                            fileUrl: f.File.ServerRelativeUrl,
                                            absoluteUrl: f.File.ServerRelativeUrl,
                                            checkedTo: f.File.CheckedOutByUser.Title,
                                            modified: f.Modified,
                                            modifiedBy: f.File.ModifiedBy.Title,
                                            createdBy: f.File.Author.Title,
                                            created: f.Created,
                                            version: f.File.UIVersionLabel
                                        };
                                        // Add file to collection 
                                        checkedOutFiles.push(fileObject);
                                    }, this);
                                })
                                .catch(e => {
                                    console.log(e);
                                });
                        });
                        // "Ideally" - When all files retrieved return collection of results 
                        d.resolve(checkedOutFiles);
                        return null;
                    })
                    .catch(e => {
                        console.log(e);
                    });
            }, this);
            return null;
        });
    return d.promise;
};

// Returns promise with all checkedout file 
getCheckedOutFiles().then(files => {
    console.log("RESULTS", files);
    d.resolve(files);
});

我注意到console.log("RESULTS", files);会在通话结束前打印出来。完成调用后，window.x将包含预期的数据。

Answer 1

使用Promise.all()等待创建的所有承诺，然后解决父承诺

像这样（未经测试）

//FIND CHECKED OUT FILES
getCheckedOutFiles = function () {
    console.log('Get checked out files');
    var d = $q.defer();

    // Store final results and pass to then callback
    var checkedOutFiles = window.x = [];

    // Promise, returns collection with all sites 
    SiteService.getAllSites()
        .then(sites => {
            // For each site get lists then get items matching filter
            sites.forEach(function (site) {
                var web = new $pnp.Web(site.url);

                return web.lists
                    .filter("BaseTemplate eq 101")
                    .get() // Returns promise with all lists matching filter 
                    .then(lists => {
                        let promises = []
                        // Go through each list and find matching item 
                        lists.forEach(function (list) {

                            let prom = web.lists.getByTitle(list.Title).items
                                .filter("CheckoutUser ne null")
                                .expand("File, File/Author, File/ModifiedBy, File/CheckedOutByUser")
                                .get() // Returns promise with all items matching filter 
                                .then(files => {
                                    // Loop through each item, get properties, add to collection 
                                    files.forEach(function (f) {
                                        var fileObject = {
                                            fileName: f.File.Name,
                                            fileUrl: f.File.ServerRelativeUrl,
                                            absoluteUrl: f.File.ServerRelativeUrl,
                                            checkedTo: f.File.CheckedOutByUser.Title,
                                            modified: f.Modified,
                                            modifiedBy: f.File.ModifiedBy.Title,
                                            createdBy: f.File.Author.Title,
                                            created: f.Created,
                                            version: f.File.UIVersionLabel
                                        };
                                        // Add file to collection 
                                        checkedOutFiles.push(fileObject);
                                    }, this);
                                })
                                .catch(e => {
                                    console.log(e);
                                });
                            promises.push(prom)
                        });
                        // "Ideally" - When all files retrieved return collection of results 
                        Promise.all(promises).then(function(){
                            d.resolve(checkedOutFiles);
                        })
                        return null;
                    })
                    .catch(e => {
                        console.log(e);
                    });
            }, this);
            return null;
        });
    return d.promise;
};

// Returns promise with all checkedout file 
getCheckedOutFiles().then(files => {
    console.log("RESULTS", files);
    d.resolve(files);
});

Answer 2

这些是需要修复的事情：

您有两个单独的循环，您有承诺管理。你需要在数组中收集这些promise，然后在它们上使用Promise.all()来知道循环中的所有promise都已完成。
您通过创建d承诺使用反模式，然后手动解析它。相反，您应该返回SiteService.getAllSites().then()承诺，然后在其中，返回承诺链，以便所有内容都链接（包括正确的错误处理）。
刚刚登录的.catch()处理程序正在“吃”错误。如果您.catch()并且不重新抛出，它会将该承诺变为已解决的承诺，从而“吃掉”错误而不是传播它。

以下是解决这些问题的方法：

//FIND CHECKED OUT FILES
function getCheckedOutFiles() {
    console.log('Get checked out files');

    // Store final results and pass to then callback
    var checkedOutFiles = window.x = [];

    // Promise, returns collection with all sites 
    return SiteService.getAllSites().then(sites => {
            // For each site get lists then get items matching filter
            var promises = [];
            sites.forEach(function (site) {
                var web = new $pnp.Web(site.url);

                promises.push(web.lists
                    .filter("BaseTemplate eq 101")
                    .get() // Returns promise with all lists matching filter 
                    .then(lists => {
                        // Go through each list and find matching item 
                        var promises2 = [];
                        lists.forEach(function (list) {
                            promises2.push(web.lists.getByTitle(list.Title).items
                                .filter("CheckoutUser ne null")
                                .expand("File, File/Author, File/ModifiedBy, File/CheckedOutByUser")
                                .get() // Returns promise with all items matching filter 
                                .then(files => {
                                    // Loop through each item, get properties, add to collection 
                                    files.forEach(function (f) {
                                        var fileObject = {
                                            fileName: f.File.Name,
                                            fileUrl: f.File.ServerRelativeUrl,
                                            absoluteUrl: f.File.ServerRelativeUrl,
                                            checkedTo: f.File.CheckedOutByUser.Title,
                                            modified: f.Modified,
                                            modifiedBy: f.File.ModifiedBy.Title,
                                            createdBy: f.File.Author.Title,
                                            created: f.Created,
                                            version: f.File.UIVersionLabel
                                        };
                                        // Add file to collection 
                                        checkedOutFiles.push(fileObject);
                                    }, this);
                                })
                                .catch(e => {
                                    console.log(e);
                                    // propagate error
                                    throw e;
                                }));
                        });
                        return Promise.all(promises2);
                    }).catch(e => {
                        console.log(e);
                        // propagate error
                        throw e;
                    }));
            }, this);
            return Promise.all(promises).then(() => {
                // make checkedOutFiles by the final resolve value
                return checkedOutFiles;
            });
        });
};

// Returns promise with all checkedout file 
getCheckedOutFiles().then(files => {
    console.log("RESULTS", files);
}).catch(err => {
    // handle error here
});

这可以通过在Bluebird promise库中使用Promise.map()来简化，它会迭代一个数组，调用一个promise产生函数并等待所有的promises完成（.each()和Promise.all()）。

使用循环中的嵌套promise来控制流

2 个答案: