In OL2 feature id's were generated internally. In OL5 this doesn't seem to be the case since the id's are undefined. Has the internal feature id been removed from OL5? If not what do I need to do to get the id's generated. I am requesting the id via:
feature.getId()
If a geoJson or other source contains feature ids they will be used, otherwise the feature id will be left undefined. You could generate your own ids if you you need them.
If the source contains a mix of features with and without id you will need to ensure your auto generated ids are unique (e.g. use a prefix).
var featureId = 0;
vector.getSource().on('addfeature', function(e){
featureId++;
if (!e.feature.getId()) {
e.feature.setId('auto-gen-'+featureId);
}
});
openlayers 5 doesn't generate the feature ID.
You have to set the feature's ID (if necessary) when creating it. Use the setId method.
Now by calling feature.getId() you will get the feature id.
It must be taken into account that in the same source of the map the id must be unique.
Related
Could I find the way to save url key by combine the sku attribute and name attribute on the time of add product. i don't want to write module or extension just need a clue how its happen on vendor/magento through code sample.
The product URL key is set in \Magento\CatalogUrlRewrite\Observer\ProductUrlKeyAutogeneratorObserver listening the catalog_product_save_before event.
The \Magento\CatalogUrlRewrite\Model\ProductUrlPathGenerator::getUrlKey method is used to generate the key.
I am pretty new to both Swift and Firebase, and I am attempting to make a simple app using Firebase as the backend. As far as I know, there is no memory-efficient way to use the numChildren() function without loading every single child into memory for counting, so I am implementing my own simple counter for the number of "Events" that have been created in my app.
The documentation for Firebase states that the childByAutoID() method should be used for updating lists in multi-user applications. I am assuming it adds a timestamp to the requested update and does them in order.
My question is whether it is necessary to use childByAutoID() when only updating a SINGLE field in a multi-user application. That is, will there be conflicts on my numEvents field if I do:
dbRef = FIRDatabase.database().reference()
dbRef.child("numEvents").setValue(num)
Or must I do:
dbRef = FIRDatabase.database().reference()
dbRef.child("numEvents").childByAutoId().setValue(num)
In order to avoid write conflicts? My only real confusion is that the documentation for childByAutoID stresses that it is useful when the children are a list of items, but mine is only a single item.
If you are only updating a single field you should not be using childByAutoId. To update a child value for an object, you need to obtain a reference to that object somehow, perhaps by a query of some sort (in many cases you will naturally already have a reference to the object if it needs to be changed) and you can change the value like this:
dbRef.child("events").child(objectToUpdateId).child(fieldToUpdateKey).setValue(newValue)
childByAutoId in this context would be used to create a new field like:
dbRef.child("events").childByAutoId().setValue(newObject)
I'm not exactly sure how this applies to your situation, but those are some descriptions of how to update a field, and use childByAutoId.
What childByAutoId does is create a unique key for a node, to avoid using the same key multiple times and then creating data conflicts like inconsistency (not write conflicts) to avoid write conflicts you use the transaction blocks.
The best way to learn is to try it out
If num == 1 , in the first example the result will be
dbRef:{
numEvents:1
}
While the second will be
dbRef:{
numEvents:{
//The auto-generated key
KLBHJBjhbjJBJHB:1
}
}
The childByAutoId would be useful if you want to save in a node multiple children of the same type, that way each children will have its own unique identifier
For example
pet:{
KJHBJJHB:{
name:fluffy,
owner:John Smith,
},
KhBHJBJjJ:{
name:fluffy,
owner:Jane Foster,
}
}
This way you have a unique identifier for cases where there is no clear way with the item data to guarantee it will be unique (in this case the pet's name)
Few things here:
childByAutoId is not a timestamp. But is used to create unique nodes in any given node.
Use case of childByAutoId :
You have messages node which stores messages from multiple user who are involved in a group chat. So each user can add messages in the group chat so you would do something like this each time user sends message:
dbRef = FIRDatabase.database().reference()
dbRef.child("messages").childByAutoId().setValue(messageText)
So this will create a unique message id for each message from different users. This will kind of act like primary key of message in normal databases.
The structure of database will be something like this:
messages: {
"randomIdGenerated-12asd12" : "hello",
"randomIdGenerated-12323D123" : "Hi, HOw are you",
}
So in your case your first approach is good enough! Since you dont need unique node for counting number of events added.
I need numeric IDs for human readability. How do I get it in Firebase?
I want numeric ID for keys, e.g. "000000001", "000000002","00000003","00000004".
The reason I need it is because these IDs will become the permanent object ID both online and offline. I want users to be able to browse that object page by just entering URL "/objects/00000001" without efforts.
I am asking here, because I want to know if this can be done without using .priority, sub-properties, etc. I guess set method can do it somehow. If it is not possible, just tell me no, I can accept that answer.
I'd suggest reading through the Firebase documentation. Specifically, see the Saving Data portion of the Firebase JavaScript Web Guide.
From the guide:
Getting the Unique ID Generated by push()
Calling push() will return a reference to the new data path, which you can use to get the value of its ID or set data to it. The following code will result in the same data as the above example, but now we'll have access to the unique push ID that was generated
// Generate a reference to a new location and add some data using push()
var newPostRef = postsRef.push({
author: "gracehop",
title: "Announcing COBOL, a New Programming Language"
});
// Get the unique ID generated by push() by accessing its key
var postID = newPostRef.key;
Source: https://firebase.google.com/docs/database/admin/save-data#section-ways-to-save
A push generates a new data path, with a server timestamp as its key. These keys look like -JiGh_31GA20JabpZBfa, so not numeric.
If you wanted to make a numeric only ID, you would make that a parameter of the object to avoid overwriting the generated key.
The keys (the paths of the new data) are guaranteed to be unique, so there's no point in overwriting them with a numeric key.
You can instead set the numeric ID as a child of the object.
You can then query objects by that ID child using Firebase Queries.
From the guide:
In JavaScript, the pattern of calling push() and then immediately calling set() is so common that we let you combine them by just passing the data to be set directly to push() as follows. Both of the following write operations will result in the same data being saved to Firebase:
// These two methods are equivalent:
postsRef.push().set({
author: "gracehop",
title: "Announcing COBOL, a New Programming Language"
});
postsRef.push({
author: "gracehop",
title: "Announcing COBOL, a New Programming Language"
});
Source: https://firebase.google.com/docs/database/admin/save-data#getting-the-unique-key-generated-by-push
As explained above, you can use the Firebase default push id.
If you want something numeric you can do something based on the timestamp to avoid collisions
f.e. something based on date,hour,second,ms, and some random int at the end
01612061353136799031
Which translates to:
016-12-06 13:53:13:679 9031
It all depends on the precision you need (social security numbers do the same with some random characters at the end of the date). Like how many transactions will be expected during the day, hour or second. You may want to lower precision to favor ease of typing.
You can also do a transaction that increments the number id, and on success you will have a unique consecutive number for that user. These can be done on the client or server side.
(https://firebase.google.com/docs/database/android/read-and-write)
Adding to the #htafoya answer.
The code snippet will be
const getTimeEpoch = () => {
return new Date().getTime().toString();
}
As the docs say, this can be achieved just by using set instead if push.
As the docs say, it is not recommended (due to possible overwrite by other user at the "same" time).
But in some cases it's helpful to have control over the feed's content including keys.
As an example of webapp in js, 193 being your id generated elsewhere, simply:
firebase.initializeApp(firebaseConfig);
var data={
"name":"Prague"
};
firebase.database().ref().child('areas').child("193").set(data);
This will overwrite any area labeled 193 or create one if it's not existing yet.
https://firebase.google.com/docs/firestore/manage-data/transactions
Use transactions and keep a number in the database somewhere that you can increase by one. This way you can get a nice numeric and simple id.
I have two jstree and dnd nodes from one to another using copy_node api. But copied nodes don't have original ids (json data ids). Auto generated ids assign them like 'j2_1'. I have original ids and want to change them with original ids. How can I implement this?
I know, it's been a while since you posted this question. However, I am working right now with jstree and had almost the same "problem".
I used data.original.id to get the original id of my copied item.
And I changed the id using $("#jstree").jstree(true).set_id(data.node,new_id);. In my case, I wanted my new id to involve the original one.
Here is my code block:
// this function is called, if I copy and paste a node
$("#jstree").bind('copy_node.jstree', function (e, data) {
var old_id= data.original.id;
// I just made a new id out of the old one, e.g. appending a number
var new_id = old_id+"1";
$("#jstree").jstree(true).set_id(data.node,new_id);
Is it possible to invalidate memcahced entries based on values.
In my app, I am assigning user in different groups and I store this mapping in memcached.
key = userID
value = groupID
So multiple userIds map to one groupID.
When I delete a particular group then I want to remove all entries in memcache store which have value as the groupID of the deleted group.
So Essentially I want to delete the entries having particular values. How do I do it.
You cannot get key's by value in memcached. What you could do though is have a key called groupID that has a comma separated userID's. If you want to see who is part of a group then you could get the key called groupID and parse out the userID's. Then if you have a key for each userID you could delete them with the parsed userID's. You could use memcached's append function too to just append the userID's to a groupID key when a new user registers for you system.
I wrote a blog post on maintaining a set a while back that may do what you're looking for.
It's essentially what mikewied is suggesting, but with more words and code samples.