I'm trying to understand how I can have nested knockoutjs view models with a little fiddle that lists some items and on click of a button, it shows the details of that item. Then, I have a button that updates the Id property of each item by adding 15 to each ones but for a reason, they end up having all the same value at the end.
Can someone enlighten me?
Thanks!
The fiddle in question
It's your .Name computed property. The Id change works correctly.
http://fiddle.jshell.net/Y3JXD/1/
The item in the closure was always the last item in the list after the first execution. Remember that the computed is updated any time the observable changes. So, the first time during setup, it worked fine as item was the item from the loop. But, what was captured in the closure was just item (the 15th item), not the one that was for that specific loop instance.
Update: forgot about the second parameter to computed as suggested in a comment.
http://fiddle.jshell.net/Y3JXD/1/
item.Name = ko.computed(function () { return 'Item_' + item.Id(); }, item);
Here's another technique for wrapping the reference in a closure, and capturing the right item instance (just as a demonstration for what needs to happen to capture the proper scope).
self.loadItems = function () {
for (var i = 0; i < 15; i++) {
var item = ko.mapping.fromJS({
Id: i
});
self.items.push(item);
(function (item) {
item.Name = ko.computed(function () {
return 'Item_' + item.Id();
});
})(item);
}
};
Could you move the Name property to the itemModel?
self.Name = ko.computed(function() {
return 'Item_' + self.Id();
});
It seems odd to set it when you create the object, rather than when you consume it.
Related
I have these two functions that should add the item onTap to the list, and then another one to delete the item. The first one (adding the item) works fine, but the delete one doesn't seem to delete anything. I suspect the issue is that the counter variable is not global, but for some reason it doesn't work fine when I add it globally (and I would need it to be). Here's the full code:
List<int> _totalPrice = [];
List<int> get totalPrice => _totalPrice;
here is the add item function
Future getTotal(item) async {
int counter = 0;
_totalPrice.add(int.parse(item));
_totalPrice.forEach((element) => counter += element);
print('LIST: $_totalPrice');
print('SUM: $counter');
return counter;
}
here is the delete function that doesn't remove anything
deleteSumItem(String item) {
_totalPrice.remove(item);
}
I think the issue is that the counter variable isn't global, I am not sure how to add it globally to change dynamically.
So, here your code shows that you are putting int in your _totalPrice list, but you are trying to remove the String from the list. It will not be found to be deleted.
So, you can change the data type of your list into String or you can write the below function to delete an item where the function only takes an int
deleteSumItem(int item) {
_totalPrice.remove(item);
}
Also you can remove an item by below line of code (If you have a custom type of data in your list):
_totalPrice.removeWhere((item) => item.price == '520')
I have a table which uses infinite scroll to load more results and append them, when the user reaches the bottom of the page.
At the moment I have the following code:
var currentPage = 0;
var tableContent = Rx.Observable.empty();
function getHTTPDataPageObservable(pageNumber) {
return Rx.Observable.fromPromise($http(...));
}
function init() {
reset();
}
function reset() {
currentPage = 0;
tableContent = Rx.Observable.empty();
appendNextPage();
}
function appendNextPage() {
if(currentPage == 0) {
tableContent = getHTTPDataPageObservable(++currentPage)
.map(function(page) { return page.content; });
} else {
tableContent = tableContent.combineLatest(
getHTTPDataPageObservable(++currentPage)
.map(function(page) { return page.content; }),
function(o1, o2) {
return o1.concat(o2);
}
)
}
}
There's one major problem:
Everytime appendNextPage is called, I get a completely new Observable which then triggers all prior HTTP calls again and again.
A minor problem is, that this code is ugly and it looks like it's too much for such a simple use case.
Questions:
How to solve this problem in a nice way?
Is is possible to combine those Observables in a different way, without triggering the whole stack again and again?
You didn't include it but I'll assume that you have some way of detecting when the user reaches the bottom of the page. An event that you can use to trigger new loads. For the sake of this answer I'll say that you have defined it somewhere as:
const nextPage = fromEvent(page, 'nextpage');
What you really want to be doing is trying to map this to a stream of one directional flow rather than sort of using the stream as a mutable object. Thus:
const pageStream = nextPage.pipe(
//Always trigger the first page to load
startWith(0),
//Load these pages asynchronously, but keep them in order
concatMap(
(_, pageNum) => from($http(...)).pipe(pluck('content'))
),
//One option of how to join the pages together
scan((pages, p) => ([...pages, p]), [])
)
;
If you need reset functionality I would suggest that you also consider wrapping that whole stream to trigger the reset.
resetPages.pipe(
// Used for the "first" reset when the page first loads
startWith(0),
//Anytime there is a reset, restart the internal stream.
switchMapTo(
nextPage.pipe(
startWith(0),
concatMap(
(_, pageNum) => from($http(...)).pipe(pluck('content'))
),
scan((pages, p) => ([...pages, p]), [])
)
).subscribe(x => /*Render page content*/);
As you can see, by refactoring to nest the logic into streams we can remove the global state that was floating around before
You can use Subject and separate the problem you are solving into 2 observables. One is for scrolling events , and the other is for retrieving data. For example:
let scrollingSubject = new Rx.Subject();
let dataSubject = new Rx.Subject();
//store the data that has been received back from server to check if a page has been
// received previously
let dataList = [];
scrollingSubject.subscribe(function(page) {
dataSubject.onNext({
pageNumber: page,
pageData: [page + 10] // the data from the server
});
});
dataSubject.subscribe(function(data) {
console.log('Received data for page ' + data.pageNumber);
dataList.push(data);
});
//scroll to page 1
scrollingSubject.onNext(1);
//scroll to page 2
scrollingSubject.onNext(2);
//scroll to page 3
scrollingSubject.onNext(3);
<script src="https://cdnjs.cloudflare.com/ajax/libs/rxjs/4.1.0/rx.all.js"></script>
I need to manipulate the text elements of the first and last tick of an axis to bring them more towards the center.
I am trying to select them, one at the time, with something like svg.select('.tick:last-child text') but it doesn't work. I'd then apply .transform('translate(4,0)')...
Am I doing something wrong? How can I achieve this?
One thing you could do is to create custom sub-selections by adding methods to d3.selection.prototype. You could create a selection.first() method that selects the first item in a selection, and a selection.last() method that selects the last item. For instance:
d3.selection.prototype.first = function() {
return d3.select(this[0][0]);
};
d3.selection.prototype.last = function() {
var last = this.size() - 1;
return d3.select(this[0][last]);
};
This would let you do the following:
var tickLabels = svg.selectAll('.tick text');
tickLabels.first()
.attr('transform','translate(4,0)');
tickLabels.last()
.attr('transform','translate(-4,0)');
Of course, you need to make sure that you only have one axis if you do it that way. Otherwise, specify the axis in your initial selection:
var tickLabels = svg.selectAll('.axis.x .tick text');
HERE is an example.
Here's the cleanest method I've found:
g.selectAll(".tick:first-of-type text").remove();
g.selectAll(".tick:last-of-type text").remove();
As google brought me here, I also want to add a cleaner method to what Adam Grey wrote.
Sometimes you just want to do it without taking a reference of selectAll .
svg.selectAll('.gridlines').filter(function(d, i,list) {
return i === list.length - 1;
}).attr('display', 'none');
the 3rd parameter of the filter function gives you the selected List of elements.
They don't exist in d3 specifically, but you can use the .firstChild and .lastChild methods on a node.
You can first select all of the parents of the node, and then operate within the scope of a .each() method, like so:
d3.selectAll('.myParentElements').each(function(d,i){
var firstChild = this.firstChild,
lastChild = this.lastChild;
//Do stuff with first and last child
});
Within the scope of .each(), this refers to the individual node, which is not wrapped by a d3 selection, so all of the standard methods on a node are available.
Using .filter() with a function also works selection.filter(filter) :
var gridlines;
gridlines = svg.selectAll('.gridlines');
gridlines.filter(function(d, i) {
return i === gridlines.size() - 1;
}).attr('display', 'none');
It's for D3.js v4
d3.selection.prototype.first = function() {
return d3.select(
this.nodes()[0]
);
};
d3.selection.prototype.last = function() {
return d3.select(
this.nodes()[this.size() - 1]
);
};
Example:
var lines = svg.selectAll('line');
lines.first()
.attr('transform','translate(4,0)');
lines.last()
.attr('transform','translate(-4,0)');
Here is another, even though I used Fered's solution for a problem I met.
d3.select(d3.selectAll('*').nodes().reverse()[0])
For example, I am randomly picking a button element from within the rows of a table.
After the button is found, I want to retrieve the table's row which contains a selected button.
Heres is my code snippet:
browser.findElements(by.css('[ng-click*=submit]')).then(function (results) {
var randomNum = Math.floor(Math.random() * results.length);
var row = results[randomNum];
// ^ Here I want to get the parent of my random button
});
As of the most recent Protractor (1.6.1 as of this writing), the syntax changed a bit:
var row = results[randomNum].element(by.xpath('..'));
(use element() instead of findElement()).
Decided to use xpath.
var row = results[randomNum].findElement(by.xpath('ancestor::tr'));
You can now use
var element = element(by.css('.foo')).getWebElement()
var parentElement = element.getDriver() // gets the parent element
to get the parent element. See http://www.protractortest.org/#/api?view=webdriver.WebElement.prototype.getDriver for more info.
Actually, at the moment there is an easier way to select the parent of an element avoiding to use xpath.
From an ElementFinder you can simply access the parent element through parentElementArrayFinder and for example then trigger directly the click method:
myElement.parentElementArrayFinder.click();
I ran into the excellent jstree jQuery UI plug in this morning. In a word - great! It is easy to use, easy to style & does what it says on the box. The one thing I have not yet been able to figure out is this - in my app I want to ensure that only one node is expanded at any given time. i.e. when the user clicks on the + button and expands a node, any previously expanded node should silently be collapsed. I need to do this in part to prevent the container div for a rather lengthy tree view from creating an ugly scrollbar on overflow and also to avoid "choice overload" for the user.
I imagine that there is some way of doing this but the good but rather terse jstree documentation has not helped me to identify the right way to do this. I would much appreciate any help.
jsTree is great but its documentation is rather dense. I eventually figured it out so here is the solution for anyone running into this thread.
Firstly, you need to bind the open_node event to the tree in question. Something along the lines of
$("tree").jstree({"themes":objTheme,"plugins":arrPlugins,"core":objCore}).
bind("open_node.jstree",function(event,data){closeOld(data)});
i.e. you configure the treeview instance and then bind the open_node event. Here I am calling the closeOld function to do the job I require - close any other node that might be open. The function goes like so
function closeOld(data)
{
var nn = data.rslt.obj;
var thisLvl = nn;
var levels = new Array();
var iex = 0;
while (-1 != thisLvl)
{
levels.push(thisLvl);
thisLvl = data.inst._get_parent(thisLvl);
iex++;
}
if (0 < ignoreExp)
{
ignoreExp--;
return;
}
$("#divElements").jstree("close_all");
ignoreExp = iex;
var len = levels.length - 1;
for (var i=len;i >=0;i--) $('#divElements').jstree('open_node',levels[i]);
}
This will correctly handle the folding of all other nodes irrespective of the nesting level of the node that has just been expanded.
A brief explanation of the steps involved
First we step back up the treeview until we reach a top level node (-1 in jstree speak) making sure that we record every ancestor node encountered in the process in the array levels
Next we collapse all the nodes in the treeview
We are now going to re-expand all of the nodees in the levels array. Whilst doing so we do not want this code to execute again. To stop that from happening we set the global ignoreEx variable to the number of nodes in levels
Finally, we step through the nodes in levels and expand each one of them
The above answer will construct tree again and again.
The below code will open the node and collapse which are already opened and it does not construct tree again.
.bind("open_node.jstree",function(event,data){
closeOld(data);
});
and closeOld function contains:
function closeOld(data)
{
if($.inArray(data.node.id, myArray)==-1){
myArray.push(data.node.id);
if(myArray.length!=1){
var arr =data.node.id+","+data.node.parents;
var res = arr.split(",");
var parentArray = new Array();
var len = myArray.length-1;
for (i = 0; i < res.length; i++) {
parentArray.push(res[i]);
}
for (var i=len;i >=0;i--){
var index = $.inArray(myArray[i], parentArray);
if(index==-1){
if(data.node.id!=myArray[i]){
$('#jstree').jstree('close_node',myArray[i]);
delete myArray[i];
}
}
}
}
}
Yet another example for jstree 3.3.2.
It uses underscore lib, feel free to adapt solution to jquery or vanillla js.
$(function () {
var tree = $('#tree');
tree.on('before_open.jstree', function (e, data) {
var remained_ids = _.union(data.node.id, data.node.parents);
var $tree = $(this);
_.each(
$tree
.jstree()
.get_json($tree, {flat: true}),
function (n) {
if (
n.state.opened &&
_.indexOf(remained_ids, n.id) == -1
) {
grid.jstree('close_node', n.id);
}
}
);
});
tree.jstree();
});
I achieved that by just using the event "before_open" and close all nodes, my tree had just one level tho, not sure if thats what you need.
$('#dtree').on('before_open.jstree', function(e, data){
$("#dtree").jstree("close_all");
});