javascript - 具有 promise 的 Ecmascript 6 递归函数

Question

我正在尝试为 sequelize.js 编写一个基类。此类将关联所有相关表。 includeFk 函数实现这个任务。但它有一个 promise ，应该是递归的。类:

class base {
    constructor(table, depth) {
        this._table = table;
        this._depth = depth;

    }

    includeFK(table, depth, includes) {
        return new Promise((resolve, reject) => {
                if (depth <= this._depth) {
                    for (var att in table.tableAttributes) {

                        table.belongsTo(m, {
                            as: m.name,
                            foreignKey: att
                        })
                        includes.push({
                            model: m
                        });

                    }
                }

                Promise.all(

                    Object.keys(table.associations).forEach(tbl => {
                            this.includeFK(table.associations[tbl].target, depth + 1, includes);
                        }

                    )).then(results => {
                    resolve(true)
                });
            } else {
                resolve(true);
            }
        });



    all(query) {
        return new Promise((resolve, reject) => {
            var tmp = this;
            var includes = [];

            Promise.all([
                this.includeFK(tmp._table, 1, includes),
                this.includeLang()
            ]).then(function() {

                tmp._table.findAll({
                    include: includes
                }).then(function(dbStatus) {
                    resolve(dbStatus);
                });
            });
        });
    }
}

错误:

(node:25079) UnhandledPromiseRejectionWarning: Unhandled promise rejection (rejection id: 3): TypeError: Cannot read property 'Symbol(Symbol.iterator)' of undefined (node:25079) DeprecationWarning: Unhandled promise rejections are deprecated. In the future, promise rejections that are not handled will terminate the Node.js process with a non-zero exit code. (node:25079) UnhandledPromiseRejectionWarning: Unhandled promise rejection (rejection id: 4): TypeError: Cannot read property 'Symbol(Symbol.iterator)' of undefined

Answer 1

您可以处理来自 Promise.all 的错误，因为它也返回一个 promise ，您需要处理它，除非您将其训练为返回的 promise 。

Promise.all([...])
    .then(...)
    .catch(function(err) {
        console.error(err);
        reject(err);
    });

编辑:

var promiseArr = [];

Object.keys(table.associations).forEach(tbl => {
  promiseArr.push(
    self.includeFK(table.associations[tbl].target, depth + 1, includes)
  );
});

Promise.all(promiseArr)
  .then(results => {
    resolve(true)
  });

我还认为您的 this 绑定(bind)不在正确的范围内。如果您遇到未定义函数的错误，请在调用类函数之前尝试使用变量引用 this。

例子:

includeFK(table, depth, includes) {
    var self = this; //ref this and use it later
  ...
      ...
           self.includeFK();