在集合中查找嵌套(嵌入)对象 [英] find nested (embedded) object in the collection
问题描述
当我在 StackOverflow 上解决我的问题时，我注意到之前也有人问过同样的问题，但他们都没有得到好的回应或实际的答案.
回到我的问题:我想找到嵌套在模式中的对象.尝试 findMany 提供所有对象，而 findOne 只提供第一个对象，但我想要通过 req.body.checkbox 传递其 ID 的特定对象.我的 JS 代码就像..
app.post("/data", uploads, function (req, res) {User.findById(req.user.id, function (err, foundUser) {如果(错误){控制台日志(错误)；} 别的 {如果(发现用户){var checkBox = req.body.checkbox;console.log(checkedBox);User.findMany({_id:foundUser._id},{comments:{$elemMatch:{_id:checkedBox}}} ,function(err,checkedobj){如果(错误){控制台日志(错误)；}别的{console.log(checkedobj.comments);如果(Array.isArray(checkedobj.comments)){res.render("checkout",{SIMG: checkedobj.comments});} 别的 {res.render("checkout",{SIMG: [checkedobj.comments]});}}})}}});});这是我的架构，供参考
const commentSchema = new mongoose.Schema({评论:字符串，图像名称:字符串，权限:{type:Number,default:0},});const Comment = new mongoose.model("Comment", commentSchema);const userSchema = new mongoose.Schema({名字:字符串，姓氏:字符串，电子邮件:字符串，密码:字符串，评论:[commentSchema]，权限:{type:Number,default:0},});userSchema.plugin(passportLocalMongoose);const User = new mongoose.model("User", userSchema);示例
<代码>{"_id" : ObjectId("5ec3f54adfaa1560c0f97cbf"),名字":q"，"姓氏" : "q","用户名": "q@q.com",盐" : "***"，哈希":***"，"__v" : NumberInt(2),注释" : [{权限":NumberInt(0),"_id" : ObjectId("5ec511e54db483837885793f"),评论":嗨"，"imagename" : "image-1589973477170.PNG"}],权限":NumberInt(1)}<块引用>
此外，当我选中 3 个复选框时，console.log(checkBox) 日志:
<预><代码>['5ec543d351e2db83481e878e','5ec589369d3e9b606446b776'，'5ec6463c4df40f79e8f1783b']
但是 console.log(checkedobj.comments) 只给出了一个对象.
<预><代码>[{权限:0，_id:5ec543d351e2db83481e878e，评论:'q'，图像名称:'图像-1589986259358.jpeg'}]当你想要一个数组中的多个匹配元素时，你应该使用 $filter 聚合运算符
作为预防措施，首先检查 req.body.checkbox 是否为数组并将其转换为 ObjectIds 数组
app.post("/data", uploads, function (req, res) {var ObjectId = mongoose.Types.ObjectId;User.findById(req.user.id, function (err, foundUser) {如果(错误){控制台日志(错误)；} 别的 {如果(发现用户){var checkBox = req.body.checkbox;如果 (!Array.isArray(checkedBox)) {选中框 = [选中框]}console.log(checkedBox);var checkedBoxArray = checkedBox.map(id => ObjectId(id))用户.聚合([{$match: {_id: foundUser._id}},{$项目:{注释: {$过滤器:{输入:$comments"，如:评论"，条件:{$in:[$$comment._id"，checkedBoxArray]}}}}}]，函数(错误，检查对象){如果(错误){控制台日志(错误)；}别的{console.log(checkedobj[0].comments);如果(Array.isArray(checkedobj[0].comments)){res.render("checkout",{SIMG: checkedobj[0].comments});} 别的 {res.render("checkout",{SIMG: [checkedobj[0].comments]});}}})}}});});工作示例 - https://mongoplayground.net/p/HnfrB6e4E3C
上面的例子将只返回 2 条与 id 匹配的评论
while i was going through my problem on StackOverflow,i noticed same question was asked before aswell,but none of them had got a good response,or an actual answer.
Mongoose Find One on Nested Object
How can I find nested objects in a document?
well back to my question: i wanted to find the object that is nested in the schema. trying findMany gives all the objects,and findOne give just the first one,but i want particular objects whose id i pass through req.body.checkbox. my JS code goes like..
app.post("/data", uploads, function (req, res) {
User.findById(req.user.id, function (err, foundUser) {
if (err) {
console.log(err);
} else {
if (foundUser) {
var checkedBox = req.body.checkbox;
console.log(checkedBox);
User.findMany({_id:foundUser._id},{comments:{$elemMatch:{_id:checkedBox}}} ,function(err,checkedobj){
if(err){
console.log(err);
}
else{
console.log(checkedobj.comments);
if (Array.isArray(checkedobj.comments)) {
res.render("checkout",{SIMG: checkedobj.comments});
} else {
res.render("checkout",{SIMG: [checkedobj.comments]});
}
}
})
}
}
});
});
here is my schema,for reference
const commentSchema = new mongoose.Schema({
comment: String,
imagename: String,
permission:{type:Number,default:0},
});
const Comment = new mongoose.model("Comment", commentSchema);
const userSchema = new mongoose.Schema({
firstname: String,
lastname: String,
email: String,
password: String,
comments: [commentSchema],
permission:{type:Number,default:0},
});
userSchema.plugin(passportLocalMongoose);
const User = new mongoose.model("User", userSchema);
example
{
"_id" : ObjectId("5ec3f54adfaa1560c0f97cbf"),
"firstname" : "q",
"lastname" : "q",
"username" : "q@q.com",
"salt" : "***",
"hash" : "***",
"__v" : NumberInt(2),
"comments" : [
{
"permission" : NumberInt(0),
"_id" : ObjectId("5ec511e54db483837885793f"),
"comment" : "hi",
"imagename" : "image-1589973477170.PNG"
}
],
"permission" : NumberInt(1)
}
also when i check 3 checkboxes, console.log(checkBox) logs:
[
'5ec543d351e2db83481e878e',
'5ec589369d3e9b606446b776',
'5ec6463c4df40f79e8f1783b'
]
but console.log(checkedobj.comments) gives only one object.
[
{
permission: 0,
_id: 5ec543d351e2db83481e878e,
comment: 'q',
imagename: 'image-1589986259358.jpeg'
}
]
When you want multiple matching elements from an array you should use $filter aggregation operator
And as a precaution, first check req.body.checkbox is an array or not and convert it into an array of ObjectIds
app.post("/data", uploads, function (req, res) {
var ObjectId = mongoose.Types.ObjectId;
User.findById(req.user.id, function (err, foundUser) {
if (err) {
console.log(err);
} else {
if (foundUser) {
var checkedBox = req.body.checkbox;
if (!Array.isArray(checkedBox)) {
checkedBox = [checkedBox]
}
console.log(checkedBox);
var checkedBoxArray = checkedBox.map(id => ObjectId(id))
User.aggregate([
{$match: {_id: foundUser._id}},
{
$project: {
comments: {
$filter: {
input: "$comments",
as: "comment",
cond: { $in: [ "$$comment._id", checkedBoxArray ] }
}
}
}
}
],function(err,checkedobj){
if(err){
console.log(err);
}
else{
console.log(checkedobj[0].comments);
if (Array.isArray(checkedobj[0].comments)) {
res.render("checkout",{SIMG: checkedobj[0].comments});
} else {
res.render("checkout",{SIMG: [checkedobj[0].comments]});
}
}
})
}
}
});
});
Working example - https://mongoplayground.net/p/HnfrB6e4E3C
Above example will return only 2 comments matching the ids
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