I am updating sort & filter models via api:
this.gridApi.setFilterModel(filterModels);
this.gridApi.setSortModel(sortModels);
The problem with this is I have a server request bound to the change even of both sort & filter so when user changes then the data is updated. This means when I change model on code like restoring a state or resetting the filters it causes multiple requests.
Is there a way to update the filter/sort model without triggering the event?
I see there is a ColumnEventType parameter but couldn't see how it works. Can I specify some variable that I can look for inside my event handlers to get them to ignore calls that are not generated from user?
I am trying to manage URL state so when url query params change my code sets the models in the grids but this ends up causing the page to reload multiple times because the onFilter and onSort events get called when the model is set and there is no way I can conceive to prevent this.
At the time, you are going to have to manage this yourself, ie, just before you call the setModel, somehow flag this in a shared part of your app (maybe a global variable)
Then when you react to these events, check the estate of this, to guess where it came from.
Note that at the moment, we have added source to the column events, but they are not yet for the model events, we are planning to add them though, but we have no ETA
Hope this helps
I had to solve similar issue. I found solution which working for my kind of situation. Maybe this help someone.
for (let j = 0; j < orders.length; j++) {
const sortModelEntry = orders[j];
if (typeof sortModelEntry.property === 'string') {
const column: Column = this.gridColumnApi.getColumn(sortModelEntry.property);
if (column && ! column.getColDef().suppressSorting) {
column.setSort(sortModelEntry.direction.toLowerCase());
column.setSortedAt(j);
}
}
this.gridApi.refreshHeader();
Where orders is array of key-value object where key is name of column and value is sorting directive (asc/desc).
Set filter without refresh was complicated
for (let j = 0; j < filters.length; j++) {
const filterModelEntry = filters[j];
if (typeof filterModelEntry.property === 'string') {
const column: Column = this.gridColumnApi.getColumn(filterModelEntry.property);
if (column && ! column.getColDef().suppressFilter) {
const filter: any = this.gridApi.getFilterApi(filterModelEntry.property);
filter['filter'] = filterModelEntry.command;
filter['defaultFilter'] = filterModelEntry.command;
filter['eTypeSelector'].value = filterModelEntry.command;
filter['filterValue'] = filterModelEntry.value;
filter['filterText'] = filterModelEntry.value;
filter['eFilterTextField'].value = filterModelEntry.value;
column.setFilterActive(true);
}
}
}
Attributes in filter:
property - name of column
command - filter action (contains, equals, ...)
value - value used in filter
For anyone else looking for a solution to this issue in Nov 2020, tapping into onFilterModified() might help. This gets called before onFilterChanged() so setting a value here (eg. hasUserManuallyChangedTheFilters = false, etc.) and checking the same in the filter changed event is a possible workaround. Although, I haven't found anything similar for onSortChanged() event, one that gets called before the sorting is applied to the grid.
I am not sure any clean way to achieve this but I noticed that FilterChangedEvent has "afterFloatingFilter = false" only if filterModel was updated from ui.
my workaround is as below
onFilterChanged = event:FilterChangedEvent) => {
if(event.afterFloatingFilter === undefined) return;
console.log("SaveFilterModel")
}
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.
My stacked area chart looks like this:
The data I used has the same number of values and is just like in the example. THe data I used is at : http://pastebin.com/D07hja76
The code I use is also almost similar appart from the selector:
var colors = d3.scale.category20();
keyColor = function(d, i) {return colors(d.key)};
nv.addGraph(function() {
chart = nv.models.stackedAreaChart()
.useInteractiveGuideline(true)
.x(function(d) { return d.t })
.y(function(d) { return d.v })
.color(keyColor)
.transitionDuration(300)
chart.xAxis
.tickFormat(function(d) { return d3.time.format('%x')(new Date(d)) });
chart.yAxis
.tickFormat(d3.format(',.0f'));
d3.select('#browserBreakdown')
.datum(browserchartdata)
.transition().duration(500)
.call(chart)
.each('start', function() {
setTimeout(function() {
d3.selectAll('#browserBreakdown *').each(function() {
if(this.__transition__)
this.__transition__.duration = 1;
})
}, 0)
})
nv.utils.windowResize(chart.update);
return chart;
});
How can I get the chart to look right?
The NVD3 chart doesn't sort your data points into a left-to-right order along your x axis, so you're getting the strange criss-crossing shape.
I assume there is some way to tell NVD3 to sort the data, but they have next to no documentation and I couldn't figure it out quickly. Instead, you can use this function to sort the data before you add it to the chart:
data.forEach(function(d,i){
d.values = d.values.sort(
function(a,b){
return +a.t -b.t;
}
);
});
How this works:
data is the array of objects from the JSON file (you would use browserchartdata);
the Javascript Array.forEach(function(){}) method calls the passed-in function for each element of the array, and passes that function the element of the array and its index;
the Javascript Array.sort() method creates a sorted version of an array using the passed-in function to determine how two elements (a and b) compare;
the sort function I created uses the .t variable (which you're using for the x-axis) from each element in your array to determine whether a is bigger than b (and therefore should go after it in the sorted array);
I call this sort function on the values array of each data line, and then write-over the unsorted values array, so that the objects in data all end up with their values sorted from smallest to largest according to t.
I tried it with your data on NVD3's "live code" site, and it looks fine.
I have a sorted mutable array of a class called Topic. The topics represent a an array of Publications. I present the topics in a table, and periodically fetch new publications from a web service. When a new publication arrives, I'd like to add to the table with an animation.
What's bothering me is the computational work I need to do to add into this array, and answer the correct index path. Can someone suggest a more direct way than this:
// add a publication to the topic model. if the publication has a new topic, answer
// the index path of the new topic
- (NSIndexPath *)addPublication:(Publication *)pub {
// first a search to fit into an existing topic
NSNumber *topicId = [pub valueForKey:#"topic_id"];
for (Topic *topic in self.topics) {
if ([topicId isEqualToNumber:[topic valueForKey:"id"]]) {
// this publication is part of an existing topic, no new index path
[topic addPublication:pub];
return nil;
}
}
// the publication must have a new topic, add a new topic (and therefore a new row)
Topic *topic = [[Topic alloc] initWithPublication:publication];
[self.topics addObject:topic];
// sort it into position
[self.topics sortUsingSelector:#selector(compareToTopic:)];
// oh no, we want to return an index path, but where did it sort to?
// yikes, another search!
NSInteger row = [self.topics indexOfObject:topic];
return [NSIndexPath indexPathForRow:row inSection:0];
}
// call this in a loop for all the publications I fetch from the server,
// collect the index paths for table animations
// so much computation, poor user's phone is going to melt!
There's no getting around the first search, I guess. But is there some more efficient way to add a new thing to an array, maintaining a sort and remembering where it got placed?
It's pretty straightforward to insert a value into a sorted list. Think about how you would insert the number "3" into the list "1, 2, 7, 9", for instance. You want to do exactly the same thing.
Loop through the array by index, using a for loop.
For each object, use compareToTopic: to compare it to the object you want to insert.
When you find the appropriate index to insert at, use -[NSArray insertObject:atIndex:] to insert it.
Then return an NSIndexPath with that index.
Edit: and, as the other answers point out, a binary search would be faster -- but definitely trickier to get right.
This is almost certainly not an issue; NSArrays are actually hashes, and search is a lot faster than it would be for a true array. How many topics can you possibly have anyways?
Still, if you measure the performance and find it poor, you could look into using a B-tree; Kurt Revis commented below with a link to a similar structure (a binary heap) in Core Foundation: CFBinaryHeap.
Another option (which would also need to be measured) might be to do the comparison as you walk the array the first time; you can mark the spot and do the insertion directly:
NSUInteger insertIndex = 0;
NSComparisonResult prevOrder = NSOrderedDescending;
for (Topic *topic in self.topics) {
NSComparisonResult order = [topicId compareToTopic:topic];
if (NSOrderedSame == order) {
// this publication is part of an existing topic, no new index path
[topic addPublication:pub];
return nil;
}
else if( prevOrder == NSOrderedDescending &&
order == NSOrderedAscending )
{
break;
}
insertIndex++;
prevOrder = order;
}
Please note that I haven't tested this, sorry.
I'm not sure this is actually better or faster than the way you've written it, though.
Don't worry about the work the computer is doing unless it's demonstrably doing it too slowly.
What you have done is correct I guess. There's another way. You can write your own binary search implementation method. (Which has only few lines of code). And you can retrieve the index where the new object should fit in. And add the new object to the required index using insertObject:atIndex: method.
I've been reading through the adobe pdf spec, along with apple's quartz 2d documentation for pdf rendering and parsing. I've also downloaded Voyeur and inspected a local pdf with it to see it's internal data. At this point I'm able to get the document catalog, and then fetch the outlines dictionary from there. I can see that nested within the outlines dictionary dictionaries that there are named "/Dest" nodes with values such as:
G1.1025588
etc
I'm wondering if there is a way for me to use these values to get a reference to page to render using some methods I've seen github projects such as Reader, along with apple documented examples.
PDF processing is definitely a challenge, so any help would be appreciated.
The /Dest entry in an outline item dictionary can either be a name, a string, or an array.
The simplest case is if it's an array; then the first item is the page object the outline entry points to (a dictionary). To get the page number, you have to iterate over all pages in the document and see which one is equal (==) to the dictionary you have (CGPDFPageRefs are actually CGPDFDictionaryRefs). You could also traverse the page tree, which is a bit harder, but may be faster (not as much as you might expect, I wouldn't optimize prematurely here). The other items in the array are position on the page etc., search for "Explicit Destinations" in the PDF spec to learn more.
If the entry is a name or string, it is a named destination. You have to map the name to a destination from the document catalog's /Dests entry which is a dictionary that contains a name tree. A name tree is essentially a tree map that allows fast access to named values without requiring to read all the data at once (as with a plain dictionary). Unfortunately, there's no direct support for name trees in Quartz, so you'll have to do a little more work to parse this structure recursively (see "Name Trees" in the PDF spec).
Note that an outline item doesn't necessarily have a /Dest entry, it can also specify its destination via an /A (action) entry, which is a little bit more complex. In most cases, however, the action will be a "GoTo" action that is essentially a wrapper for a destination.
The mapping of names to destinations can also be stored as a plain dictionary. In that case, it's in the /Dests entry of the /Names dictionary in the document's catalog. I've rarely seen this though and it was deprecated after PDF 1.2 (current is 1.7).
You will definitely need the PDF spec for this: http://www.adobe.com/content/dam/Adobe/en/devnet/pdf/pdfs/PDF32000_2008.pdf
Thanks to Omz, here is a piece of code to retreive a page number for an outline destination in a PDF file :
// Get Page Number from an array
- (int) getPageNumberFromArray:(CGPDFArrayRef)array ofPdfDoc:(CGPDFDocumentRef)pdfDoc withNumberOfPages:(int)numberOfPages
{
int pageNumber = -1;
// Page number reference is the first element of array (el 0)
CGPDFDictionaryRef pageDic;
CGPDFArrayGetDictionary(array, 0, &pageDic);
// page searching
for (int p=1; p<=numberOfPages; p++)
{
CGPDFPageRef page = CGPDFDocumentGetPage(pdfDoc, p);
if (CGPDFPageGetDictionary(page) == pageDic)
{
pageNumber = p;
break;
}
}
return pageNumber;
}
// Get page number from an outline. Only support "Dest" and "A" entries
- (int) getPageNumber:(CGPDFDictionaryRef)node ofPdfDoc:(CGPDFDocumentRef)pdfDoc withNumberOfPages:(int)numberOfPages
{
int pageNumber = -1;
CGPDFArrayRef destArray;
CGPDFDictionaryRef dicoActions;
if(CGPDFDictionaryGetArray(node, "Dest", &destArray))
{
pageNumber = [self getPageNumberFromArray:destArray ofPdfDoc:pdfDoc withNumberOfPages:numberOfPages];
}
else if(CGPDFDictionaryGetDictionary(node, "A", &dicoActions))
{
const char * typeOfActionConstChar;
CGPDFDictionaryGetName(dicoActions, "S", &typeOfActionConstChar);
NSString * typeOfAction = [NSString stringWithUTF8String:typeOfActionConstChar];
if([typeOfAction isEqualToString:#"GoTo"]) // only support "GoTo" entry. See PDF spec p653
{
CGPDFArrayRef dArray;
if(CGPDFDictionaryGetArray(dicoActions, "D", &dArray))
{
pageNumber = [self getPageNumberFromArray:dArray ofPdfDoc:pdfDoc withNumberOfPages:numberOfPages];
}
}
}
return pageNumber;
}