I have a following code.
void onItemSelected(String status) {
print("default list count: " + transactionList.length.toString());
List<trx.Transaction> filteredTrx = transactionList;
print("default2 list count: " + transactionList.length.toString());
filteredTrx.retainWhere((element) => element.status == status);
print("default3 list count: " + transactionList.length.toString());
filteredTransactionList = filteredTrx;
}
I am doing a dropdownbutton to allow user to filter based on their status selection. In this example, the status of the transaction can be (processing, approved, rejected).
I know that I can use foreach loop to compare and assign into a new list. But i would like to use a function which is more efficient. And i think that retainWhere could be a good solution for it.
So, I had a list of Transactions recorded into transactionList variable. And to prevent this list from changing, i declare a new list to store into it and apply it with retainWhere function. However, i noticed that once it runs the retainWhere function, the default transactionList will be empty as well. Does anyone know why?
The debug result is as below:
I/flutter (12068): default list count: 2
I/flutter (12068): default2 list count: 2
I/flutter (12068): default3 list count: 0
You are not copying the list, you are copying the reference to same list (see the second sentence here: https://dart.dev/guides/language/language-tour#variables). This is the reason why both lists are affected by retainWhere.
You probably want to (shallow) copy the list like this:
List<trx.Transaction> filteredTrx = List.from(transactionList)
https://api.dart.dev/stable/2.18.0/dart-core/List/List.from.html
I am using firestore to retrieve data
List<Data> userSearchItems = [];
...........
for (var i = 0; i<userDocument['order'].length; i++)...[
Text(userDocument["order"][i].toString()),
userSearchItems.add(userDocument["order"][i].toString()),//This do not work a read line appears with error
],
errors seen for userDocument["order"][i].toString()
The argument type 'String' can't be assigned to the parameter type 'Data'
and a red line also appears at add
Using for loop i can get the Text but i want to store it in an array or list (what is most suitable) to be used later to get data from firestore that match a list/array item that has been fetched before
Found the solution
You can implement a new method for it
var arr=List();
void addList() {
FirebaseFirestore.instance.collection("points").doc('1').get().then((value){
arr.addAll(value['order']);
});
}
and the list can be used in any other function
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.
Scala is pretty new for me and I have problems as soon as a leave the gatling dsl.
In my case I call an API (Mailhog) which responds with a lot of mails in json-format. I can’t grab all the values.
I need it with “jsonPath” and I need to “regex” as well.
That leads into a map and a list which I need to iterate through and save each value.
.check(jsonPath("$[*]").ofType[Map[String,Any]].findAll.saveAs("id_map"))
.check(regex("href=3D\\\\\"(.*?)\\\\\"").findAll.saveAs("url_list"))
At first I wanted to loop the “checks” but I did’nt find any to repeat them without repeating the “get”-request too. So it’s a map and a list.
1) I need every value of the map and was able to solve the problem with the following foreach loop.
.foreach("${id_map}", "idx") {
exec(session => {
val idMap = session("idx").as[Map[String,Any]]
val ID = idMap("ID")
session.set("ID", ID)
})
.exec(http("Test")
.get("/{ID}"))
})}
2) I need every 3rd value of the list and make a get-request on them. Before I can do this, I need to replace a part of the string. I tried to replace parts of the string while checking for them. But it won’t work with findAll.
.check(regex("href=3D\\\\\"(.*?)\\\\\"").findAll.transform(raw => raw.replace("""=\r\n""","")).saveAs("url"))
How can I replace a part of every string in my list?
also how can I make a get-request on every 3rd element in the list.
I can't get it to work with the same foreach structure above.
I was abole to solve the problem by myself. At first I made a little change to my check(regex ...) part.
.check(regex("href=3D\\\\\"(.*?)\\\\\"").findAll.transform(_.map(raw => raw.replace("""=\r\n""",""))).saveAs("url_list"))
Then I wanted to make a Get-Request only on every third element of my list (because the URLs I extracted appeared three times per Mail).
.exec(session => {
val url_list =
session("url_list").as[List[Any]].grouped(3).map(_.head).toList
session.set("url_list", url_list)
})
At the end I iterate through my final list with a foreach-loop.
foreach("${url_list}", "urls") {
exec(http("Activate User")
.get("${urls}")
)
}
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.