I started a macOS project using Default configuration of CoreData. Application was released and some users started to use it. Now, I need some data to be synced with iCloud and some data to be only stored locally. If I understand correctly, the only way I can achieve this is to create two different configurations (in CoreData data model), add the needed entities in each configuration, and configure the NSPersistentContainer accordingly.
However the above method might lead to some data loss since I wont be using the Default configuration anymore.
Is there any way I can "migrate" the data saved under the Default configuration to another configuration?
After some trial and error I found a solution that seems to do the work (however, it seems dirty).
First, when instantiating the container, I make sure I add my 3 storeDescriptors to persistentStoreDescriptions (each representing an scheme)
let defaultDirectoryURL = NSPersistentContainer.defaultDirectoryURL()
var persistentStoreDescriptions: [NSPersistentStoreDescription] = []
let localStoreLocation = defaultDirectoryURL.appendingPathComponent("Local.sqlite")
let localStoreDescription = NSPersistentStoreDescription(url: localStoreLocation)
localStoreDescription.cloudKitContainerOptions = nil
localStoreDescription.configuration = "Local"
persistentStoreDescriptions.append(localStoreDescription)
let cloudStoreLocation = defaultDirectoryURL.appendingPathComponent("Cloud.sqlite")
let cloudStoreDescription = NSPersistentStoreDescription(url: cloudStoreLocation)
cloudStoreDescription.configuration = "iCloud"
cloudStoreDescription.cloudKitContainerOptions = "iCloud.com.xxx.yyy"
persistentStoreDescriptions.append(cloudStoreDescription)
let defaultStoreLocation = defaultDirectoryURL.appendingPathComponent("Default.sqlite")
let defaultStoreDescription = NSPersistentStoreDescription(url: defaultStoreLocation)
defaultStoreDescription.cloudKitContainerOptions = nil
defaultStoreDescription.configuration = "Default"
persistentStoreDescriptions.append(defaultStoreDescription)
container.persistentStoreDescriptions = persistentStoreDescriptions
Note: One important thing is to make sure that NSPersistentStoreDescription with the Default configuration is added last.
Secondly, I am for-eaching thought all data saved in core data checking if managedObject.objectID.persistentStore?.configurationName is "Default" (or any string containing Default. With my empiric implementation I got to the conclusion that configuration name might be different from case to case). If the above condition is true, create a new managedObject, I copy all properties from the old one to new one, delete the old managed object, and save the context.
for oldManagedObject in managedObjectRepository.getAll() {
guard let configurationName = oldManagedObject.objectID.persistentStore?.configurationName else {
continue
}
if (configurationName == "Default") {
let newManagedObject = managedObjectRepository.newManagedObject()
newManagedObject.uuid = oldManagedObject.uuid
newManagedObject.createDate = oldManagedObject.createDate
......
managedObjectRepository.delete(item: oldManagedObject)
managedObjectRepository.saveContext()
}
}
With this implementation, old data that was previously saved in Default.sqlite is now saved in Local.sqlite or 'Cloud.sqlite' (depending on which configuration contains which entity).
I am working on a project and would like to have some initial data loaded to Core Data. There are two attributes in the Core Data. First belongs to body part and second belongs to its property. Such as Eyes to have one of the four colors and so forth. The data will be like following:
Eyes Blue
Eyes Brown
Eyes Green
Eyes Black
Hair Red
Hair Brunette
Hair Blonde
Clothes Dress
Clothes Skirt
Clothes Shoes
Clothes Hat
Clothes Gloves
I have searched some CSV or pList versions and heard some sqLite shipment alternatives but couldn't figure out how to do them effectively.
I appreciate any clear explanation to load small initial data to Core Data and also removing any duplicate value from Core Data, if exists. Thank you in advance.
Here is some very basic code to show one simple way of doing this.
You need to add your own identifier attribute so you can check if an item already exists. Let's say you call that id.
Then, when you start your app, you check for each of your default values and if they don't already exist, add them, like this:
// create a fetch request to get all items with id=1
let fr = NSFetchRequest<MyItem>(entityName: MyItem.entity().name!)
fr.predicate = NSPredicate(format: "id == %#", "1")
do {
// if that request returns no results
if (try myManagedObjectContext.fetch(fr).isEmpty == true) {
// create the default item
let item = NSEntityDescription.insertNewObject(forEntityName: MyItem.entity().name!, into: myManagedObjectContext) as! MyItem
// set the id
item.id = "1"
// set other attributes here
}
} catch {
// fetching failed, handle the error
}
After adding the data, you have to save it:
// save the context
do {
try myManagedObjectContext.save()
} catch {
// handle the error
}
You could also use Core Datas Unique Constraints, but I think this solution is much simpler. Hope this helps!
I've read all the documentation I can find and watched all the videos I can find and don't understand how to do this. I have set up an xPages REST Service and it works well. Now I want to place the results of the service into either a combobox or typeahead text field. Ideally I would like to know how to do it for both types of fields.
I have an application which has a view containing a list of countries, another view containing a list of states, and another containing a list of cities. I would like the first field to only display the countries field from the list of data it returns in the XPages REST Service. Then, depending upon which country was selected, I would like the states for that country to be listed in another field for selection, etc.
I can see code for calling the REST Service results from a button, or from a dojo grid, but I cannot find how to call it to populate either of the types of fields identified above.
Where would I call the Service for the field? I had thought it would go in the Data area, but perhaps I've just not found the right syntax to use.
November 6, 2017:
I have been following your suggestion, but am still lost as can be. Here's what I currently have in my code:
x$( "#{id:ApplCountry}" ).select2({
placeholder: "select a country",
minimumInputLength: 2,
allowClear : true,
multiple: false,
ajax: {
dataType: 'text/plain',
url: "./Application.xsp/gridData",
quietMillis: 250,
data: function (params) {
return {
search:'[name=]*'+params.term+'*',
page: params.page
};
},
processResults: function (data, page) {
var data = $.map(data, function (obj) {
obj.id = obj.id || obj["#entityid"];
obj.text = obj.text || obj.name;
return obj;
});
},
return {results: data};
}
}
});
I'm using the dataType of 'text/plain' because that was what I understood I should use when gathering data from a domino application. I have tried changing this to json but it makes no difference.
I'm using processResults because I understand this is what should be used in version 4 of select2.
I don't understand the whole use of the hidden field, so I've stayed away from that.
No matter what I do, although my REST service works if I put it directly in the url, I cannot get any data to display in the field. All I want to display in the field is the country code of the document, which is in the field named "name" (not my choice, it's how it came before I imported the data from MySQL.
I have read documentation and watched videos, but still don't really understand how everything fits together. That was my problem with the REST service. If you use it in Dojo, you just put the name of the service in a field on the Dojo element and it's done, so I don't understand why all the additional coding for another type of domino element. Shouldn't it work the same way?
I should point out that at some points it does display the default message, so it does find the field. Just doesn't display the country selections.
I think the issue may be that you are not returning SelectItems to your select2, and that is what it is expecting. When I do something like you are trying, I actually use a bean to generate the selection choices. You may want to try that or I'm putting in the working part of my bean below.
The Utils.getItemValueAsString is a method I use to return either the string value of a field, or if it is not on the document/empty/null an empty string. I took out an if that doesn't relate to this, so there my be a mismatch, but I hope not.
You might be able to jump directly to populating the arrayList, but as I recall I needed to leverage the LinkedHashMap for something.
You should be able to do the same using SSJS, but since that renders to Java before executing, I find this more efficient.
For label/value pairs:
LinkedHashMap lhmap = new LinkedHashMap();
Document doc = null;
Document tmpDoc = null;
allObjects.addElement(doc);
if (dc.getCount() > 0) {
doc = dc.getFirstDocument();
while (doc != null) {
lhmap.put(Utils.getItemValueAsString(doc, LabelField, true), Utils.getItemValueAsString(doc, ValueField, true));
}
tmpDoc = dc.getNextDocument(doc);
doc.recycle();
doc = tmpDoc;
}
}
List<SelectItem> options = new ArrayList<SelectItem>();
Set set = lhmap.entrySet();
Iterator hsItr = set.iterator();
while (hsItr.hasNext()) {
Map.Entry me = (Map.Entry) hsItr.next();
// System.out.println("after: " + hStr);
SelectItem option = new SelectItem();
option.setLabel(me.getKey() + "");
option.setValue(me.getValue() + "");
options.add(option);
}
System.out.println("About to return from generating");
return options;
}
I ended up using straight up SSJS. Worked like a charm - very simple.
I'm trying to test out Firebase to allow users to post comments using push. I want to display the data I retrieve with the following;
fbl.child('sell').limit(20).on("value", function(fbdata) {
// handle data display here
}
The problem is the data is returned in order of oldest to newest - I want it in reversed order. Can Firebase do this?
Since this answer was written, Firebase has added a feature that allows ordering by any child or by value. So there are now four ways to order data: by key, by value, by priority, or by the value of any named child. See this blog post that introduces the new ordering capabilities.
The basic approaches remain the same though:
1. Add a child property with the inverted timestamp and then order on that.
2. Read the children in ascending order and then invert them on the client.
Firebase supports retrieving child nodes of a collection in two ways:
by name
by priority
What you're getting now is by name, which happens to be chronological. That's no coincidence btw: when you push an item into a collection, the name is generated to ensure the children are ordered in this way. To quote the Firebase documentation for push:
The unique name generated by push() is prefixed with a client-generated timestamp so that the resulting list will be chronologically-sorted.
The Firebase guide on ordered data has this to say on the topic:
How Data is Ordered
By default, children at a Firebase node are sorted lexicographically by name. Using push() can generate child names that naturally sort chronologically, but many applications require their data to be sorted in other ways. Firebase lets developers specify the ordering of items in a list by specifying a custom priority for each item.
The simplest way to get the behavior you want is to also specify an always-decreasing priority when you add the item:
var ref = new Firebase('https://your.firebaseio.com/sell');
var item = ref.push();
item.setWithPriority(yourObject, 0 - Date.now());
Update
You'll also have to retrieve the children differently:
fbl.child('sell').startAt().limitToLast(20).on('child_added', function(fbdata) {
console.log(fbdata.exportVal());
})
In my test using on('child_added' ensures that the last few children added are returned in reverse chronological order. Using on('value' on the other hand, returns them in the order of their name.
Be sure to read the section "Reading ordered data", which explains the usage of the child_* events to retrieve (ordered) children.
A bin to demonstrate this: http://jsbin.com/nonawe/3/watch?js,console
Since firebase 2.0.x you can use limitLast() to achieve that:
fbl.child('sell').orderByValue().limitLast(20).on("value", function(fbdataSnapshot) {
// fbdataSnapshot is returned in the ascending order
// you will still need to order these 20 items in
// in a descending order
}
Here's a link to the announcement: More querying capabilities in Firebase
To augment Frank's answer, it's also possible to grab the most recent records--even if you haven't bothered to order them using priorities--by simply using endAt().limit(x) like this demo:
var fb = new Firebase(URL);
// listen for all changes and update
fb.endAt().limit(100).on('value', update);
// print the output of our array
function update(snap) {
var list = [];
snap.forEach(function(ss) {
var data = ss.val();
data['.priority'] = ss.getPriority();
data['.name'] = ss.name();
list.unshift(data);
});
// print/process the results...
}
Note that this is quite performant even up to perhaps a thousand records (assuming the payloads are small). For more robust usages, Frank's answer is authoritative and much more scalable.
This brute force can also be optimized to work with bigger data or more records by doing things like monitoring child_added/child_removed/child_moved events in lieu of value, and using a debounce to apply DOM updates in bulk instead of individually.
DOM updates, naturally, are a stinker regardless of the approach, once you get into the hundreds of elements, so the debounce approach (or a React.js solution, which is essentially an uber debounce) is a great tool to have.
There is really no way but seems we have the recyclerview we can have this
query=mCommentsReference.orderByChild("date_added");
query.keepSynced(true);
// Initialize Views
mRecyclerView = (RecyclerView) view.findViewById(R.id.recyclerView);
mManager = new LinearLayoutManager(getContext());
// mManager.setReverseLayout(false);
mManager.setReverseLayout(true);
mManager.setStackFromEnd(true);
mRecyclerView.setHasFixedSize(true);
mRecyclerView.setLayoutManager(mManager);
I have a date variable (long) and wanted to keep the newest items on top of the list. So what I did was:
Add a new long field 'dateInverse'
Add a new method called 'getDateInverse', which just returns: Long.MAX_VALUE - date;
Create my query with: .orderByChild("dateInverse")
Presto! :p
You are searching limitTolast(Int x) .This will give you the last "x" higher elements of your database (they are in ascending order) but they are the "x" higher elements
if you got in your database {10,300,150,240,2,24,220}
this method:
myFirebaseRef.orderByChild("highScore").limitToLast(4)
will retrive you : {150,220,240,300}
In Android there is a way to actually reverse the data in an Arraylist of objects through the Adapter. In my case I could not use the LayoutManager to reverse the results in descending order since I was using a horizontal Recyclerview to display the data. Setting the following parameters to the recyclerview messed up my UI experience:
llManager.setReverseLayout(true);
llManager.setStackFromEnd(true);
The only working way I found around this was through the BindViewHolder method of the RecyclerView adapter:
#Override
public void onBindViewHolder(final RecyclerView.ViewHolder holder, int position) {
final SuperPost superPost = superList.get(getItemCount() - position - 1);
}
Hope this answer will help all the devs out there who are struggling with this issue in Firebase.
Firebase: How to display a thread of items in reverse order with a limit for each request and an indicator for a "load more" button.
This will get the last 10 items of the list
FBRef.child("childName")
.limitToLast(loadMoreLimit) // loadMoreLimit = 10 for example
This will get the last 10 items. Grab the id of the last record in the list and save for the load more functionality. Next, convert the collection of objects into and an array and do a list.reverse().
LOAD MORE Functionality: The next call will do two things, it will get the next sequence of list items based on the reference id from the first request and give you an indicator if you need to display the "load more" button.
this.FBRef
.child("childName")
.endAt(null, lastThreadId) // Get this from the previous step
.limitToLast(loadMoreLimit+2)
You will need to strip the first and last item of this object collection. The first item is the reference to get this list. The last item is an indicator for the show more button.
I have a bunch of other logic that will keep everything clean. You will need to add this code only for the load more functionality.
list = snapObjectAsArray; // The list is an array from snapObject
lastItemId = key; // get the first key of the list
if (list.length < loadMoreLimit+1) {
lastItemId = false;
}
if (list.length > loadMoreLimit+1) {
list.pop();
}
if (list.length > loadMoreLimit) {
list.shift();
}
// Return the list.reverse() and lastItemId
// If lastItemId is an ID, it will be used for the next reference and a flag to show the "load more" button.
}
I'm using ReactFire for easy Firebase integration.
Basically, it helps me storing the datas into the component state, as an array. Then, all I have to use is the reverse() function (read more)
Here is how I achieve this :
import React, { Component, PropTypes } from 'react';
import ReactMixin from 'react-mixin';
import ReactFireMixin from 'reactfire';
import Firebase from '../../../utils/firebaseUtils'; // Firebase.initializeApp(config);
#ReactMixin.decorate(ReactFireMixin)
export default class Add extends Component {
constructor(args) {
super(args);
this.state = {
articles: []
};
}
componentWillMount() {
let ref = Firebase.database().ref('articles').orderByChild('insertDate').limitToLast(10);
this.bindAsArray(ref, 'articles'); // bind retrieved data to this.state.articles
}
render() {
return (
<div>
{
this.state.articles.reverse().map(function(article) {
return <div>{article.title}</div>
})
}
</div>
);
}
}
There is a better way. You should order by negative server timestamp. How to get negative server timestamp even offline? There is an hidden field which helps. Related snippet from documentation:
var offsetRef = new Firebase("https://<YOUR-FIREBASE-APP>.firebaseio.com/.info/serverTimeOffset");
offsetRef.on("value", function(snap) {
var offset = snap.val();
var estimatedServerTimeMs = new Date().getTime() + offset;
});
To add to Dave Vávra's answer, I use a negative timestamp as my sort_key like so
Setting
const timestamp = new Date().getTime();
const data = {
name: 'John Doe',
city: 'New York',
sort_key: timestamp * -1 // Gets the negative value of the timestamp
}
Getting
const ref = firebase.database().ref('business-images').child(id);
const query = ref.orderByChild('sort_key');
return $firebaseArray(query); // AngularFire function
This fetches all objects from newest to oldest. You can also $indexOn the sortKey to make it run even faster
I had this problem too, I found a very simple solution to this that doesn't involved manipulating the data in anyway. If you are rending the result to the DOM, in a list of some sort. You can use flexbox and setup a class to reverse the elements in their container.
.reverse {
display: flex;
flex-direction: column-reverse;
}
myarray.reverse(); or this.myitems = items.map(item => item).reverse();
I did this by prepend.
query.orderByChild('sell').limitToLast(4).on("value", function(snapshot){
snapshot.forEach(function (childSnapshot) {
// PREPEND
});
});
Someone has pointed out that there are 2 ways to do this:
Manipulate the data client-side
Make a query that will order the data
The easiest way that I have found to do this is to use option 1, but through a LinkedList. I just append each of the objects to the front of the stack. It is flexible enough to still allow the list to be used in a ListView or RecyclerView. This way even though they come in order oldest to newest, you can still view, or retrieve, newest to oldest.
You can add a column named orderColumn where you save time as
Long refrenceTime = "large future time";
Long currentTime = "currentTime";
Long order = refrenceTime - currentTime;
now save Long order in column named orderColumn and when you retrieve data
as orderBy(orderColumn) you will get what you need.
just use reverse() on the array , suppose if you are storing the values to an array items[] then do a this.items.reverse()
ref.subscribe(snapshots => {
this.loading.dismiss();
this.items = [];
snapshots.forEach(snapshot => {
this.items.push(snapshot);
});
**this.items.reverse();**
},
For me it was limitToLast that worked. I also found out that limitLast is NOT a function:)
const query = messagesRef.orderBy('createdAt', 'asc').limitToLast(25);
The above is what worked for me.
PRINT in reverse order
Let's think outside the box... If your information will be printed directly into user's screen (without any content that needs to be modified in a consecutive order, like a sum or something), simply print from bottom to top.
So, instead of inserting each new block of content to the end of the print space (A += B), add that block to the beginning (A = B+A).
If you'll include the elements as a consecutive ordered list, the DOM can put the numbers for you if you insert each element as a List Item (<li>) inside an Ordered Lists (<ol>).
This way you save space from your database, avoiding unnecesary reversed data.
I am using EF 6 Code First and I need to delete an item and then also update a different item within a collection of Entities. If I try to delete one item and then modify a completely different item I get the error message "An object with the same key already exists in the ObjectStateManage" This is inaccurate because there are two objects with completely different PK IDs but when the update happens it throws the error. If I comment out the code to delete then the update works just fine with multiple items to update. Why would it complain about the "same key" when the keys are different?
foreach (var phone in phones)
{
if (!_isValidPhone(phone))
{
if(phone.PhoneId != 0)
{
var deletePhone = _db.Phones.FirstOrDefault(r => r.PhoneId == phone.PhoneId);
_db.Entry(deletePhone).State = EntityState.Deleted;
continue;
}
}
if (_isNewPhone(phone))
{
AddNewPhone(phone, _person);
}
else
{
UpdatePhoneData(phone, _person.Phones.FirstOrDefault(r => r.Order == phone.Order));
}
}
private void UpdatePhoneData(Phone phoneFrom, Phone phoneTo)
{
phoneTo.Note = phoneFrom.Note;
phoneTo.PhoneNumber = phoneFrom.PhoneNumber;
phoneTo.Order = phoneFrom.Order;
_db.Entry(phoneTo).State = EntityState.Modified;
}
If a phone is not valid and has id you try to add it to the context in two ways:
While deleting it:
_db.Entry(deletePhone).State = EntityState.Deleted;
Besides, when checking if it's new or not you either add or update it. Thats the problem.
So, what you need to do is wrap the add or update part inside an else, to add or update only if the phone has not been deleted.
This is not really a logic issue, the phone that was being updated is completely different than the phone that was being deleted. The issue is in the object statemanager. Because I was doing this in the delete
var deletePhone = _db.Phones.FirstOrDefault();
And then later I had a separate list of Phones where I try to set one of them to modified
_db.Entry(phoneTo).State = EntityState.Modified;
Well the object state manager now has each phone loaded twice basically. So if I just use the _person.Phones for both my delete and modify, then the Phones list is only loaded once and there are now duplicate keys.
_db.Entry(_person.Phones.FirstOrDefault(r => r.PhoneId == phone.PhoneId)).State = EntityState.Deleted;