node.js - findOne 返回一个空对象
问题描述
我试图通过 查找和删除子文档_id
,但它总是返回 null。
这是我的User
架构:
// Create sub-document schema for items
var itemSchema = new mongoose.Schema ({
type: String,
colour: String,
material: String,
brand: String,
_id: String,
})
// Main user schema (incl. wardrobe)
const userSchema = new mongoose.Schema({
email: { type: String, unique: true },
password: String,
passwordResetToken: String,
passwordResetExpires: Date,
facebook: String,
twitter: String,
google: String,
github: String,
instagram: String,
linkedin: String,
steam: String,
tokens: Array,
profile: {
name: String,
gender: String,
location: String,
website: String,
picture: String
},
wardrobe: {
items: [[itemSchema]]
}
}, { timestamps: true });
这是一个示例对象:
{
"_id": {
"$oid": "5c16d181c15a68c14fe2f2d3"
},
"wardrobe": {
"items": [
[
{
"type": "T-shirt",
"colour": "Black",
"material": "Wool",
"brand": "Adidas",
"_id": "5c1827dcc13025f86gfdf053"
}
],
[
{
"type": "T-shirt",
"colour": "Black",
"material": "Cotton",
"brand": "Puma",
"_id": "5c1827dfc13025f86dfaf075"
}
]
]
},
"tokens": [],
"email": "test@test.com",
"password": "$2a$10$tyCl4frHgAA1m8p6Y6kAkeAbjdYK1SJ5ghnlvWCF/MAb9.hMfR2/a",
"createdAt": {
"$date": "2018-12-16T22:28:17.777Z"
},
"updatedAt": {
"$date": "2018-12-17T23:10:02.301Z"
},
"__v": 16,
"profile": {
"gender": "",
"location": "",
"name": "Test",
"website": ""
}
}
这就是我的使用方式findOne
:
exports.deleteItem = (req, res, next) => {
User.findOne({"wardrobe.items._id": "5c1827dfc13025f86dfaf075"}, (err, item) => {
console.log(item);
if (err) {
return console.log("error: " + err);
}
res.redirect('/wardrobe');
});
};
console.log(item)
始终返回 null,即使 id 字段是现有文档。有任何想法吗?
解决方案
经过多次试验和错误,结果证明$elemMatch
是我需要的。这将返回整个对象:
exports.deleteItem = (req, res, next) => {
User.findOne({ 'wardrobe.items': { $elemMatch: { "_id": "5c1985359db5074cb3da562d",} } }, {wardrobe:1}, (err, item) => {
console.log(item);
if (err) {
return console.log("error: " + err);
}
res.redirect('/wardrobe');
});
};
但是我不想要整个对象,我想要_id
搜索到的特定对象。但这是另一个问题。
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