I have this code in IndexedDB:
var request = objectStore.add({ entryType: entryType, entryDate: t});
Now I want to know the key of this record that was just added in. How do I do that?
I found this article, and this
code:
var data = {"bookName" : "Name", "price" : 100, "rating":"good"};
var request = objectStore.add(data);
request.onsuccess = function(event){
document.write("Saved with id ", event.result)
var key = event.result;
};
This does not work for me - key shows up as undefined. I think I am missing something basic here!
Go through this code
var data = {"bookName" : "Name", "price" : 100, "rating":"good"};
var request = objectStore.add(data);
request.onsuccess = function(event){
document.write("Saved with id ", event.result)
var key = event.target.result;
};
Hope this code will work to retrieve key of last inserted Record
The spec is written for user agent, not for developer. So it is confusing. Key generator is provided by the user agent.
Any event object that is received by onsuccess handler always have event.target.result. It is the key you are looking for. The key is auto generated if you don't provide it, assuming you set autoIncrement to true.
It is documented in Step 8: as follow:
The result of this algorithm is key.
The trick here is knowing how to search using phrases iteratively, until you land on what you need. I've never heard of IndexedDB before, but seem to have found what you want.
I put "IndexedDB" into a search engine and found this. That yielded the phrase "key generator", so I searched for that as well which led me to this and this.
The StackOverflow link discusses using UUIDs, which of course can be generated in JavaScript, and the last link appears to have examples to do what you want out of the box.
If you're using the idb Promise wrapper for IndexedDB then the new key is just the return value from the add() call:
import { openDB } from 'idb';
const db = await openDB(...);
const tx = db.transaction('mystore', 'readwrite');
const newId = await tx.store.add({ hello: 'world' });
await tx.done;
console.log(`Autogenerated unique key for new object is ${newId}`);
Remember of course, this will only work if you include autoIncrement: true in the options passed to createObjectStore().
Related
I'm trying to make a user send their num to another user.
I created a random keycode for every user to send each other a num.
I tried accessing the data by querying them.
const sendNum = async(e) => {
const userCol = collection(db, "users")
e.preventDefault();
const targetQuery = query(userCol, where("keycode", "==", target))
const targetSnapshot = await getDocs(targetQuery)
targetSnapshot.forEach((doc) => {
console.log(doc.data().num);
})
console.log(targetSnapshot);
But it returns an object rather than the another user's num field
Nu {_firestore: xc, _userDataWriter: ah, _snapshot: Oo, metadata: Su, query: Ic}
Here's what the data looks like:
Posting the solution suggested by Doug Stevenson as a Community Wiki for visibility.
From the description it's not possible to tell what value the target holds.
In this case, hard coding the value worked to access the user field.
To summarize, I am working with 2 collections - 'usercollection' and 'groupcollection' and I would like to associate users with groups. I don't want to have 2 copies of all the user documents so I have a unique ID attribute for each user that I want to use to associate specific users with specific groups. This is all running on a localhost webserver so I'm getting the input from an html page with a form in it where you enter 'username' and 'groupname'. I tried using the .distinct() function with query as 'username' and the target field/attribute as 'uid'.
// Set our internal DB variable
var db = req.db;
// Get our form values. These rely on the "name" attributes
var userName = req.body.username;
// Set query and options for searching usercollection
var query = {"username" : userName};
const fieldName = "uid";
// Set our collections
var users = db.get('usercollection');
// Get UID corresponding to username
var uidToAdd = users.distinct(fieldName, query);
This is what I attempted (with some other lines that aren't relevant taken out) but it just returned a null object so I'm at a bit of a loss. Also, I'm still a beginner with nodejs/javascript/mongoDB so the more informative the answer the better! When I do the same code in the mongo shell I can get the actual value of the 'uid' attribute so I really don't know what's going wrong
I am not sure I am following you. But if I understood correctly, if you want to make a relationship between 'usercollection' and 'groupcolletion', you can simply create those 2 collections and each user in 'usercollection' should have a field with 'groupid' as a reference. In this way, you can access 'groupcollection' easily.
Here is an example with using mongoose.
In User model
...
groupId: {
type: mongoose.Schema.Types.ObjectID
ref: "Group"
}
...
Later you can also use 'populate' to fetch 'Group' information.
...
let data = await User.findById(id).populate('groupId');
...
I've got a little app that allows me to upload files, one at a time, to firebase storage. In the process it creates a database reference where it stores the user that uploaded it, the downlodurl etc.
However I have hit an issue as I want to serve back to the user their uploads at random, which is not something easily done by firebase DB at the moment (it would seem - happy to be proven wrong though!!) so I was wondering if it was possible on upload to create a numeric index field that auto increments after every upload?
Would it be as simple as querying the database pulling the max value for the current index and then +1 to it?
Below is the (fairly boilerplate) database referencing bit of the code where I would want to add the index number:
var imagekey = firebase.database().ref('images/').push().key;
var downloadURL = uploadTask.snapshot.downloadURL;
var updates = {};
var postData = {
url: downloadURL,
index:
user: user.uid
};
updates ['/images/'+imagekey] = postData;
firebase.database().ref().update(updates);
});
Ok thanks to the help of Frank below I was able to write the following function to create a data base reference of "index" and increase it by one on every single upload:
var indexRef = firebase.database().ref('index');
indexRef.transaction(function(currentRank) {
return currentRank + 1;
});
However it did have an incredibly odd effect when inserted into my upload function - the upload would continue to work, the file would appear in storage - but only the index database reference would be written, all other information would be lost and I would get an incredibly complex error in the console. Here is the updated code - any ideas as to what I may have done incorrectly?
function complete(){
//write a database reference
var indexRef = firebase.database().ref('index');
indexRef.transaction(function(currentRank) {
return currentRank + 1;
});
var imagekey = firebase.database().ref('images/').push().key;
var downloadURL = uploadTask.snapshot.downloadURL;
var updates = {};
var postData = {
url: downloadURL,
score: 1500,
index: indexRef,
user: user.uid
};
updates ['/images/'+imagekey] = postData;
firebase.database().ref().update(updates);
});
}
If you want to write a value to the database, based on a value that is currently in the database, you'll use transactions.
The trickiest bit with transactions is that they work on a single location in the database. With the data model you propose, you'd be reading from one post (highest index so far) to then write to another one. That would mean that you need a transaction on the entire images node, which is a huge problem for scalability.
What you'll likely want to do is keep a "highest used counter value" somewhere in a single spot and then "claim next value and write updated value" on that in a transaction. That means read-and-update the counter in a transaction, and then write the image with the index you just claimed.
Thanks for looking at my question. It should be easy for anyone who has used Meteor in production, I am still at the learning stage.
So my meteor setup is I have a bunch of documents with ownedBy _id's reflecting which user owns each document (https://github.com/rgstephens/base/tree/extendDoc is the full github, note that it is the extendDoc branch and not the master branch).
I now want to modify my API such that I can display the real name of each owner of the document. On the server side I can access this with Meteor.users.findOne({ownedBy}) but on the client side I have discovered that I cannot do this due to Meteor security protocols (a user doesnt have access to another user's data).
So I have two options:
somehow modify the result of what I am publishing to include the user's real name on the server side
somehow push the full user data to the clientside and do the mapping of the _id to the real names on the clientside
what is the best practice here? I have tried both and here are my results so far:
I have failed here. This is very 'Node' thinking I know. I can access user data on clientside but Meteor insists that my publications must return cursors and not JSON objects. How do I transform JSON objects into cursors or otherwise circumvent this publish restriction? Google is strangely silent on this topic.
Meteor.publish('documents.listAll', function docPub() {
let documents = Documents.find({}).fetch();
documents = documents.map((x) => {
const userobject = Meteor.users.findOne({ _id: x.ownedBy });
const x2 = x;
if (userobject) {
x2.userobject = userobject.profile;
}
return x2;
});
return documents; //this causes error due to not being a cursor
}
I have succeeded here but I suspect at the cost of a massive security hole. I simply modified my publish to be an array of cursors, as below:
Meteor.publish('documents.listAll', function docPub() {
return [Documents.find({}),
Meteor.users.find({}),
];
});
I would really like to do 1 because I sense there is a big security hole in 2, but please advise on how I should do it? thanks very much.
yes, you are right to not want to publish full user objects to the client. but you can certainly publish a subset of the full user object, using the "fields" on the options, which is the 2nd argument of find(). on my project, i created a "public profile" area on each user; that makes it easy to know what things about a user we can publish to other users.
there are several ways to approach getting this data to the client. you've already found one: returning multiple cursors from a publish.
in the example below, i'm returning all the documents, and a subset of all the user object who own those documents. this example assumes that the user's name, and whatever other info you decide is "public," is in a field called publicInfo that's part of the Meteor.user object:
Meteor.publish('documents.listAll', function() {
let documentCursor = Documents.find({});
let ownerIds = documentCursor.map(function(d) {
return d.ownedBy;
});
let uniqueOwnerIds = _.uniq(ownerIds);
let profileCursor = Meteor.users.find(
{
_id: {$in: uniqueOwnerIds}
},
{
fields: {publicInfo: 1}
});
return [documentCursor, profileCursor];
});
In the MeteorChef slack channel, #distalx responded thusly:
Hi, you are using fetch and fetch return all matching documents as an Array.
I think if you just use find - w/o fetch it will do it.
Meteor.publish('documents.listAll', function docPub() {
let cursor = Documents.find({});
let DocsWithUserObject = cursor.filter((doc) => {
const userobject = Meteor.users.findOne({ _id: doc.ownedBy });
if (userobject) {
doc.userobject = userobject.profile;
return doc
}
});
return DocsWithUserObject;
}
I am going to try this.
I have code that, when a user is logged in, selects recipes that apply to him based on the ingredients (items) he has previously identified identified as possessions.
This code gets the id's of the items the user already has:
if request.user.is_authenticated():
user_items = [possession.item for possession in request.user.possession_set.all()]
user_items_ids = [item.id for item in user_items]
uids = set(user_items_ids)
The following code, which already existed, is where I run into problems...
recipes = [(recipe, len(set([item.id for item in recipe.items.all()]) & uids), recipe.votes) for recipe in recipes]
I created another part of the site that allows people who have not yet signed up to just pick a few ingredients. I do this with some jQuery on the front end, then send the results to the backend:
var ingredient_set = [];
$('.temp_ingredient').each(function(index){
ingredient_set[index] = $(this).attr('id').substr(4);
});
$.get('/recipes/discover', { 'ingredients': ingredient_set },
function(){
alert("Success");
});
The problem is when I receive them on the Django side, with this code:
uids = request.GET['ingredients']
I get the following error:
unsupported operand type(s) for &: 'set' and 'unicode'
Basically, I know they aren't in the same format, but I don't know how to get them to be compatible.
You are sending a JavaScript array in the query string of your GET request. Therefore you should use request.GET.getlist. Just using request.GET[key] gives you the last value for that key.
>> request.GET['foo[]']
u'5'
>> request.GET.getlist('foo[]')
[u'1', u'2', u'4', u'5']
Note that the values are unicode, but you probably need them as integers, so be sure to convert them.
uids = request.GET.getlist('foo[]')
uids = set([int(x) for x in uids])
I'm not sure why my key is actually foo[] and not just foo, but as you get no KeyError, request.GET.getlist('ingredients') should work.