There seems to be a difference between
can.Component.extend({
viewModel: {
items: new Model.List(),
updateItems: function(viewModel) {
viewModel.attr('items', new Model.List({}));
}
}
and
can.Component.extend({
viewModel: {
items: new Model.List(),
updateItems: function(viewModel) {
Model.findAll({}, function(items) {
viewModel.attr('items', items);
});
}
}
in that the former triggers change events on items but the latter does not, please see jsfiddle.
Could someone explain why? As far as I understand the docs both new Model.List() and Model.findAll() return a can.Model.List.
No event is triggered when the result is an empty list. Should this not trigger at least the length event?
Just to be clear, Model.findAll() returns a promise that resolves to a list.
The reason is that:
Model.findAll({}, function(items) {
viewModel.attr('items', items);
});
Doesn't actually change 'items' length. 'items' is set to a list that already has a length, and that length never changes. So no, "{items} length" doesn't callback when items or the length changes, only when the current 'items' length changes.
This is different than:
viewModel.attr('items', new Model.List({}));
Which sets 'items' to an initially empty list. Later that list is updated with items, which changes the 'items' list's length property.
Related
I have a subject which emits a string value and the code is as below: when the components get initialized, the subjectTypeSubject is null. But there is another method in a component get subscribed to this observable where i set isLoading to true. Because the finalize is not getting called, the loading is always set to true. How to make it work so it gets completed when the value is null as well.
private subjectTypeSubject = new BehaviorSubject<string>(null);
private getPage() {
this.subjectTypeSubject.pipe(
filter((selectedSubjectType) => {
console.log('subject type', selectedSubjectType); //first time it comes as null. so it wont go inside switchmap.
return selectedSubjectType && selectedSubjectType !== '';
}),
switchMap((selectedSubjectType) => {
return this.customListsService
.getCustomListItemsByTypeName()
}),
map((customItemsData) => {
return customItemsData
})
);
}
private _getPage(pageNumber: number, search: string) {
this.loading = true;
this._pageSubscription = this.getPage({
pageSize: this._config.pageSize,
pageNumber,
search
})
.pipe(finalize(() => (this.loading = false))) //this is not called
.subscribe((p) => {
this._currentPage = p.pageNumber;
this.options = p.options;
this._allLoaded = p.isLast;
this.loading = false;
});
}
Adding a takeWhile() instead of filter worked for me. If there is any other better solution. please let me know. thanks
BehaviorSubject doesn't complete unless you complete it
There are multiple ways to call complete an observable in a pipe. take, takeWhile and takeUntil are some of them. Calling .complete on the BehaviorSubject is also an option.
But you should ask yourself: is this really what you want to achieve here? After completion it's not possible to pass any data to the subscription, even if the initial BehaviorSubject emits a new value.
One thing that this strange about your code: it should not work at all. In getPage() you are creating a new observable (by piping the BehaviorSubject), but you are not returning it. Therefore it should return undefined. It‘s also a little bit odd that you are using pipe in a function call. You should either declare the pipe during initialization or directly subscribe to a newly created observable.
This is my current object which i need to update:
[
{ id: q1,
answers:[
{ id: a1,
answered: false
},
...
]
},
...
]
I can't figure out how to update this object and set for example answered = true.
Is there any better way saving this kind of object? I tried to use the update addon from React but can't get it to work properly.
You can update the answers list this way, in your reducer:
function update(state, action) {
// assuming you are passing an id of the item to be updated via action.itemId
let obj = state.whatever_list.filter(item => item.id === action.itemId)[0]
//assuming you are passing an id of the answer to be updated via action.answerId
//also, assuming action.payload contains {answered: true}
let answers = obj.answers.map(answer => answer.id === action.answerId ?
Object.assign({}, answer, action.payload) : answer)
obj = Object.assign({}, obj, {answers: answers})
return {
whatever_list: state.whatever_list.map(item => item.id == action.itemId? Object.assign({}, item, obj) : item)
}
}
Here is what your action might look like:
function updateAnswer(itemId, answerId, payload) {
return {
type: UPDATE_ANSWER,
itemId: itemId,
answerId: answerId,
payload: payload
}
}
In your react component class, assuming there is an event handler for monitoring whether if a question is answered:
export default class Whatever extends React.Component {
...
// assuming your props contains itemId and answerId
handleAnswered = (e) => {
this.props.dispatch(updateAnswer(this.props.itemId, this.props.answerId, {answered: true}))
}
...
}
So basically what happens is this:
Your event handler calls the action and pass the updated data to it
When your action is called, it returns the updated data along with a type parameter
When your reducer sees the type parameter, the corresponding handler will be triggered (the first piece of the code above)
The reducer will pull out the existing data from the list, replace the old data with the new one, and then return a list containing the new data
You can create a sub-reducer for the answers key. Look at this example:
https://github.com/rackt/redux/blob/master/examples/async/reducers/index.js
You could use dot-prop-immutable and an update would be as simple as:
return dotProp.set(state, 'quiz.0.answers.0.answered', true);
I have the following issues with my knockout model validations and not sure how to resolve them. Following is my model first of all, with the validation rules:
var Data = function (data) {
this.Val = data;
}
function ViewModel(item) {
var parse = JSON.parse(item.d);
var self = this;
this.Name = ko.observable(parse.Name);
this.UserType = ko.observable(parse.UserType);
this.ID = ko.observable(parse.ID).extend({ required: { params: true, message: "ID is required" }, decimal: { params: 2, message: "Should be decimal"} });
this.Username = ko.observable(parsed.Username).extend({ required: {
onlyIf: function () {
return self.UserType() > 1;
}
}
});
this.WeeklyData = ko.observableArray([]);
var records = $.map(parse.WeeklyData, function (data) { return new Data(data) });
this.WeeklyData(records);
this.WeeklyData2 = ko.observableArray([]);
var records = $.map(parse.WeeklyData2, function (data) { return new Data(data) });
this.WeeklyData2(records);
}
ko.extenders.numeric = function (target, precision) {
var result = ko.dependentObservable({
read: function () {
return target().toFixed(precision);
},
write: target
});
result.raw = target;
return result;
};
Here are my problems:
1) with the ID() observable, I want to restrict it to two decimal points, so I've created the validation extender 'numeric' but it's not working. Is there anything wrong with how I'm using it and how to correct it?
2) Also, if I want to restrict an observable to whole numbers, how can I do that?
3) when I define a rule with a condition, (i.e. Username()), how do I define a custom message for that? I was able to do it for default rules, but with the conditional rules, it's not working
4) I have two observable arrays WeeklyData1 and WeeklyData2 both of which contains Data() objects. I want to have separate min/max rules for these two, for example, min/max - 1,7 for WeeklyData1 and min/max - 1,150 for WeeklyData2. How can I get it done?
4) Right now my error messages appear right next to the data field, but I want all those to appear in a single validation summary, while displaying '*' against the field. I've been told to use Validation-bindings, but I'm not sure how to use it, can someone please give an example?
It's a lot of questions, I know, but I appreciate if someone could help.
Thanks in advance
Instead of diving in your code i have created a small-small demonstrations for your questions. Ok so here we go,
1) with the ID() observable, I want to restrict it to two decimal points.... and 2) Also, if I want to restrict an observable to whole numbers....
Your 1 and 2 question are pretty similar so i covered both of this in a single fiddle. Check this fiddle.
3) when I define a rule with a condition, (i.e. Username()), how do I define a custom message ....
You can use message property to set custom messages, Check this fiddle.
4) I have two observable arrays WeeklyData1 and WeeklyData2 both of which contains Data() objects
I am not clear which this question, what type of data both of these array contains and for what you want to set min/max rule ( array length or other ). So please clear this, than i will try to help on this.
5) Right now my error messages appear right next to the data field.....
This questions answer i already given in your how to? with knockout js validations question (Check update).
Let me know if it helps!
I have a collection which contains several items that should be accessible in a list.
So every element in the collection gets it own view element which is then added to the DOM into one container.
My question is:
How do I apply the sort order I achieved in the collection with a comparator function to the DOM?
The first rendering is easy: you iterate through the collection and create all views which are then appended to the container element in the correct order.
But what if models get changed and are re-ordered by the collection? What if elements are added? I don't want to re-render ALL elements but rather update/move only the necessary DOM nodes.
model add
The path where elements are added is rather simple, as you get the index in the options when a model gets added to a collection. This index is the sorted index, based on that if you have a straightforward view, it should be easy to insert your view at a certain index.
sort attribute change
This one is a bit tricky, and I don't have an answer handy (and I've struggled with this at times as well) because the collection doesn't automatically reshuffle its order after you change an attribute the model got sorted on when you initially added it.
from the backbone docs:
Collections with comparator functions will not automatically re-sort
if you later change model attributes, so you may wish to call sort
after changing model attributes that would affect the order.
so if you call sort on a collection it will trigger a reset event which you can hook into to trigger a redraw of the whole list.
It's highly ineffective when dealing with lists that are fairly long and can seriously reduce user experience or even induce hangs
So the few things you get walking away from this is knowing you can:
always find the index of a model after sorting by calling collection.indexOf(model)
get the index of a model from an add event (3rd argument)
Edit:
After thinking about if for a bit I came up with something like this:
var Model = Backbone.Model.extend({
initialize: function () {
this.bind('change:name', this.onChangeName, this);
},
onChangeName: function ()
{
var index, newIndex;
index = this.collection.indexOf(this);
this.collection.sort({silent: true});
newIndex = this.collection.indexOf(this);
if (index !== newIndex)
{
this.trigger('reindex', newIndex);
// or
// this.collection.trigger('reindex', this, newIndex);
}
}
});
and then in your view you could listen to
var View = Backbone.View.extend({
initialize: function () {
this.model.bind('reindex', this.onReindex, this);
},
onReindex: function (newIndex)
{
// execute some code that puts the view in the right place ilke
$("ul li").eq(newIndex).after(this.$el);
}
});
Thanks Vincent for an awesome solution. There's however a problem with the moving of the element, depending on which direction the reindexed element is moving. If it's moving down, the index of the new location doesn't match the index of what's in the DOM. This fixes it:
var Model = Backbone.Model.extend({
initialize: function () {
this.bind('change:name', this.onChangeName, this);
},
onChangeName: function () {
var fromIndex, toIndex;
fromIndex = this.collection.indexOf(this);
this.collection.sort({silent: true});
toIndex = this.collection.indexOf(this);
if (fromIndex !== toIndex)
{
this.trigger('reindex', fromIndex, toIndex);
// or
// this.collection.trigger('reindex', this, fromIndex, toIndex);
}
}
});
And the example listening part:
var View = Backbone.View.extend({
initialize: function () {
this.model.bind('reindex', this.onReindex, this);
},
onReindex: function (fromIndex, toIndex) {
var $movingEl, $replacingEl;
$movingEl = this.$el;
$replacingEl = $("ul li").eq(newIndex);
if (fromIndex < toIndex) {
$replacingEl.after($movingEl);
} else {
$replacingEl.before($movingEl);
}
}
});
I have an array containing objects. Each object has an id field. I want to implement a function that deletes an object by specifying the id. I use .each from prototypejs on the array to step through the objects and check the id. If it matches, how do I actually delete it? I've tried setting the object returned from .each to null, but using FireBug I see that the object is still the same in the array.
EDIT: the objects in the array may in turn contain arrays with objects that may need to be deleted. My function is fine for finding the object to be removed, and I use splice to remove it (using a counter). It seems to me that .each (and the other enumerators like .reject) returns a copy of the object. If I set the object to null then upon inspection the object is still in the array. How would I return a reference of the object that when set to null would actually operate on the object in the array, and not a copy?
Here is the function, the deleteChild function works on the same principal:
function removeControl(controlName) {
var counter = 0;
cont.each(function (existingControl) {
if (existingControl.id == controlName) {
existingControl.destroy();
cont.splice(counter, 1);
}
else { // not found, check control's children
existingControl.deleteChild(controlName);
}
counter++;
}, this);
}
Only use .each when you want to do something to every object. Semantically speaking, you should be using Enumerable.reject in this situation. Think how much easier it will be to understand when you have to fix it in years' time.
function deleteById(objects, id) {
return objects.reject(function(obj) {
return obj.id == id;
}).each(function(obj) {
obj.deleteChild(id);
});
}