回调地狱，末日金字塔，node.js

Question

我是节点的新手，在我完成API后，我意识到所有的API都是一团糟，都是回调地狱，这迫使我学习promise，现在一切都很好，直到我面对一个API，它有多个可能的函数，我的问题是如何做嵌套的promise，我的代码是关于一个有用户附加到它的父对象，当调用删除路由时，有许多条件：

1. 如果此父级有附属的子级，则不应将其删除

2. 无子

   a。该父对象在多个学校中，school_id从父对象的学校id和附加到它的用户对象中删除

   b。如果该家长没有孩子，并且只在school_id上，则应该删除该家长，并且还应该删除附加的用户

代码看起来像这样，它是100%功能

router.post('/delete',Validation, function (req, res) {
var school_id = req.body.schoolId;
var parent_id = req.body.selected[0];
/
Student.findOne({parent_ids:parent_id},function(err,parentF){
if(err){
console.log(err);
res.json({status:"error",message:"an error occurred"});
return
}else if(parentF){
res.json({status:"error", message:"you can not delete a parent who has students associated with it"});
return;
}else{
Parent.findOne({_id:parent_id},function(err,parent){
if(err){
console.log(err);
res.json({status:"error",message:"an error occurred"});
return;
}else{
if(parent.school_id.length>1){
var a = parent.school_id.indexOf(school_id);
parent.school_id.pop(a);
parent.save(function(err,parent){
if(err){
console.log(err);
res.json({status:"error",message:"an error occurred"});
return;
}else{
User.findOne({refid:parent_id},function(err,user){
if(err){
console.log(err);
res.json({status:"error",message:"an error occurred"});
return;
}else {
user.school_id.pop(a);
user.save(function(err) {
if(err){
console.log(err);
res.json({status:"error",message:"an error occurred"});
return;
}else{
res.json({status: "success", message: "parent removed"});
return;
}
});
}
});
}
});
}else{
Parent.remove({_id: parent_id}, function (err) {
if (err) {
res.json({status: "error", message: err.message});
} else {
User.remove({refid:parent_id},function(err){
if (err) {
res.json({status: "error", message: "parent user wasn't deleted"});
return;
}else{
res.json({status: "success", message: "parent data successfully deleted"});
return;
}
});
}
});
}
}
});
}
});
});

我正在尝试应用promise并使我的代码变得更好。

很抱歉问了这么长的问题，但我遇到了麻烦，任何建议都很感激

Answer 1

为findOne创建一些"promise"风格的函数，删除并保存

let findOneP = (object, params) => new Promise((resolve, reject) => {
object.findOne(params, (err, data) => {
if (err) {
return reject(err);
}
resolve(data);
});
});
let removeP = (object, params) => new Promise((resolve, reject) => {
object.remove(params, (err, data) => {
if (err) {
return reject(err);
}
resolve(data);
});
});
let saveP = (object) => new Promise((resolve, reject) => {
object.save((err, data) => {
if (err) {
return reject(err);
}
resolve(data);
});
});

使用Bluebird Promisify可以更容易地完成上述操作，但由于您尚未指定Bluebird，因此我只使用了一个快速而肮脏的promise包装

然后使用承诺链让生活变得轻松

router.post('/delete',Validation, function (req, res) {
var school_id = req.body.schoolId;
var parent_id = req.body.selected[0];
findOneP(Student, {parent_ids: parent_id})
.then(parentF => {
if (parentF) {
throw "you can not delete a parent who has students associated with it";
}
})
.then(() => findOneP(Parent, {_id: parent_id}))
.then(parent => {
if (parent.school_id.length > 1) {
var a = parent.school_id.indexOf(school_id);
parent.school_id.pop(a);
return saveP(parent)
.then(parent => findOneP(User, {refid: parent_id}))
.then(user => saveP(user))
.then(() => "parent removed");
}
return removeP(Parent,{_id: parent_id})
.then(() => removeP(User, {refid: parent_id}))
.then(() => "parent data successfully deleted");
})
.then(message => res.json({status: "success",message}))
.catch(message => res.json({status: "error",message}));
});

我刚刚读到你使用节点4.2-你可能需要

1. 通过像babel这样的运输车运行
2. 加载Promise库，如bluebird

如果使用bluebird，请使用它的promisify函数，而不是"手动"promising