[英]Auto-increment field in Mongoose
我正在嘗試使用 Mongoose 創建一個 API,我有一個模型,我想在其中自動增加 postID 的值。 我有帖子模式
const PostSchema = new Schema({
title: {
type: String,
required: true
},
postID: {
type: Number,
unique: true,
required: true
},
body: {
type: String,
required: true
},
author: {
type: Schema.Types.ObjectId,
ref: 'Author',
required: true
},
dateCreated: {
type: Date,
required: true
},
lastModified: {
type: Date,
required: false
},
modifiedBy: {
type: Schema.Types.ObjectId,
ref: 'Author',
required: false
},
picture: {
type: mongoose.SchemaTypes.Url,
required: false
}
}, {collection: 'Post'});
我創建了一個預先保存的鈎子
export const PostModel = mongoose.model('Post', PostSchema);
PostSchema.pre('save', true, async function (next) {
const post = this;
post._id = new ObjectID();
post.dateCreated = new Date();
try {
const lastPost = await PostModel.find({postID: {$exists: true}}).sort({id: -1}).limit(1);
post.postID = lastPost.postID + 1;
} catch (e){
console.log('could not take the last post')
}
if(post && post.hasOwnProperty('body') && !post.body.isModified){
return next();
}
if(post && post.hasOwnProperty('body') && post.body.isModified){
post.lastModified = new Date();
return next();
}
});
處理添加創建日期,並自動增加 postID。 但是,每當我向 API 發送更改以創建新帖子時,我都會收到一個錯誤: Post validation failed: dateCreated: Path dateCreated is required., id: Path id is required.
這意味着 pre-save hook 中處理的任何工作都沒有完成。 每當我向解析器添加一些隨機值時,突變就會成功完成。 知道為什么預存不起作用嗎?
這是我的解析器
module.exports.addPost = async(_,args, req) => {
const post = new PostModel({
title: args.post.title,
body: args.post.body,
author: new ObjectID(args.post.author),
picture: args.post.picture
});
try {
return await post.save();
} catch (e) {
console.log('Could not save the post');
console.log(e);
}
};
這里的突變
curl 'http://localhost:3001/graphql' -H 'Accept-Encoding: gzip, deflate, br' -H 'Content-Type: application/json' -H 'Accept: application/json' -H 'Connection: keep-alive' -H 'DNT: 1' -H 'Origin: http://localhost:3001' --data-binary '{"query":"mutation($post: PostInput){\n addPost(post: $post){\n title\n body\n author\n }\n}","variables":{"post":{"title":"newTitle","body":"Lorem ipsum","author":"5e07e6c07156cb000092ab45","picture":"http://www.example.com"}}}' --compressed
上面的代碼段將不起作用。 根據 Mongoose 的文檔,在編譯模型后調用 pre 或 post 鈎子不起作用。 所以你應該搬家
export const PostModel = mongoose.model('Post', PostSchema);
低於預鈎。 此外,由於PostModel
尚未定義,並且您想要獲取插入到數據庫中的對象的最后一個 id,您可以將此檢查移至您的解析器。
let lastPost = await PostModel.find({id: {$exists: true}}).sort({id: -1}).limit(1);
// This always returns an array, either empty or with data
if(Array.isArray(lastPost) && lastPost.length > 0){
lastPost = lastPost[0]
}
const post = new PostModel({
...
id: lastPost['id'] + 1
...
});
if(Array.isArray(lastPost) && lastPost.length === 0) {
post.id = 0;
// If this lastPost is an empty array and you try to access the id property
// you will get an error that NaN to Int conversion failed
}
希望這可以幫助
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