Develop Reference

Why isn't my svelte {#each} block reactive?

So basically I am playing with Svelte trying to spin up a quick app, details of the app aren't important but basically it hosts a bunch of embedded sites. see example here & for replicability:
https://svelte.dev/repl/6f3484554ef8489b9a5960487a0a1f95?version=3.47.0
My problem is that when I add a new url & title to the sites list, the {#each} block that creates the embedded views doesn't update to reflect the new state of the list, even though the list is clearly updating in the console output. Is it something to do with scope or is it a Svelte issue of not triggering reactivity on prop reassignments from components?
Update: some sites don't allow embedding so use https://wikipedia.org as a safe one for testing.
if you replace a hard-coded url in the sites list with wiki address it should work fine. i basically want a new window to pop up as the {#each} block creates a new SiteView component

There are several things wrong with your code, the first being that you do not propagate the changes made to the sites array back to the main application, you should use bind: to keep the two arrays in sync.
<InputBar bind:sites {site} />
The second is that you are modifying an object when adding a new site and then adding that object to the array, this will always be the same object so if you change it the previously added sites will also change. You can solve this by spreading the new object into the array instead:
function add() { sites = sites.concat({...site}); console.log(sites)}
// or alternatively
function add() { sites = [...sites, {...site}]; console.log(sites); }
That said, the application is not very "Svelte" like as it mixes responsibilities and exposes data to components that don't need that data. For example, why would the input bar need to know about the current sites ? It would be a lot better to have the input bar be just that, an input bar. When the user clicks 'add' it raises an event that says 'something has been added' and resets the fields. Then the parent is responsible to add it to the array. This will make for a more flexible solution. If you do that you will see there is also no reason to have a 'site' variable on the top level (or even have that object at all, you can just have two fields)
<script>
import { createEventDispatcher } from 'svelte'
let url = ''
let title = ''
const dispatch = createEventDispatcher()
function add() {
dispatch('add', { url, title })
url = ''
title = ''
}
</script>
<div class="rounded">
<p>Enter a site to stream:</p>
<input type="text" placeholder="www.example.com" bind:value={url}>
<br>
<input type="text" placeholder="example" bind:value={title}>
<button on:click={add}>add</button>
</div>
<InputBar on:add={(ev) => sites = [...sites, ev.detail]} />
On a final note, to add things to the head of the html use <svelte:head> instead.

If you want to change a value from another component you need to bind the property, otherwise the relationship is one-way only (from parent component to child).
<InputBar bind:sites {site}/>

Detect When a object changes Angular 5

I'm trying to detect when ever an object changes. The object is connected to a large form. Whenever a user changes the input I would like it to have save/cancel buttons popup at the bottom of the page.
My idea was to just make a copy of the object and do *ngIf="object !== object_copy" and if they hit cancel set the data equal to the copied object. I don't know if this the proper way to do it since I will be using it twice as many variables for a small task, but I've only used angular for a short time. I can't get this method to work however because when ever I make a type copy the object losses it's type.
Can someone help me with this or figure out a better way to do this?

If you are using a Form, then you could take advantage of Angular's form control, which will tell you anytime a form and any of its values have been altered in any way. Then, you could do something as simple as:
form.dirty
or even specific fields. There are tons of things you can do with reactive and template forms from Angular.
https://angular.io/guide/forms

You have to subscribe an event to handle the change event:
constructor(private formBuilder: FormBuilder) {
this.myForm = formBuilder.group({
name: 'Jose Anibal Rodriguez',
age: 23
})
this.myForm.valueChanges.subscribe(data => {
console.log('Form changes', data);
})
}
It should works.

ReactiveForm supports the dirty property. You can use 'myForm.dirty' to check the dirty status of the form.
Otherwise, you can set the initial value of the form to an object property using the getRawValue() method
this.initailFormValue = this.myForm.getRawValue();
Then just subscribe the form changes using
myForm.valueChanges.subscribe((value) => {
this.updatedFormValue = this.myForm.getRawValue();
},
(err) => {
//
}
);
Now you have the initial and current form values. You can compare and do the remaining.

How to use reactive forms inside ng-template

I have just started with Angular 4 and I need to develop a CRUD grid, where the user can add, edit or delete rows.
During my research I found this article where it shows how to create the grid and also the actions: Angular 4 Grid with CRUD operations.
Looking at his code, what called my attention was the way he is using the ng-template to toggle between edit/view mode.
<tr *ngFor="let emp of EMPLOYEES;let i=idx">
<ng-template [ngTemplateOutlet]="loadTemplate(emp)" [ngOutletContext]="{ $implicit: emp, idx: i }"></ng-template>
</tr>
On the article he uses template driven forms to edit the row. However, I was trying to change to reactive forms.
In my attempt to do that, I tried to replace the [(ngModel)] to formControlName and I got some errors. My first attempt I tried to add the [formGroup] at the beginning of the template html inside form element. But when I tried to run and edit the row, I got the following error:
Error: formControlName must be used with a parent formGroup directive. You'll want to add a formGroup directive and pass it an existing FormGroup instance (you can create one in your class).
When I tried to move the [formGroup] inside the ng-template it works, however I was not able to bind the value to the fields and I had to set the values in the loadTemplate function:
loadTemplate(emp: Employee) {
if (this.selemp && this.selemp.id === emp.id) {
this.rForm.setValue({
id: emp.id,
name: emp.name
});
return this.editTemplate;
} else {
return this.readOnlyTemplate;
}
}
This works and show the values inside the fields in a read only mode :(
Here is the Plunker of what I have got so far.
How can I make a reactive form work with ng-template and how to set values to edit the entries?
Any help is appreciated! Thanks

Actually your form is not readonly, you are just constantly overwriting the input you are entering. Since you are having a method call in template (which is usually not a good idea), loadTemplate gets called whenever changes happen, which in it's turn means that
this.rForm.setValue({
id: emp.id,
name: emp.name
});
gets called over and over whenever you try and type anything. We can overcome this with instead setting the form values when you click to edit. Here we also store the index so that we can use it to set the modified values in the correct place in array, utilizing the index could perhaps be done in a smarter way, but this is a quick solution to achieve what we want.
editEmployee(emp: Employee) {
this.index = this.EMPLOYEES.indexOf(emp)
this.selemp = emp;
this.rForm.setValue({
id: emp.id,
name: emp.name
});
}
so when we click save, we use that index...
saveEmp(formValues) {
this.EMPLOYEES[this.index] = formValues;
this.selemp = null;
this.rForm.setValue({
id: '',
name: ''
});
}
Your plunker: https://plnkr.co/edit/6QyPmqsbUd6gzi2RhgPp?p=preview
BUT notice...
I would suggest you perhaps rethink this idea, having the method loadTemplate in template, will cause this method to fire way too much. You can see in the plunker, where we console log fired! whenever it is fired, so it is a lot! Depending on the case, this can cause serious performance issues, so keep that in mind :)
PS. Made some other changes to code for adding a new employee to work properly (not relevant to question)

I want an action that links me to the Object clicked in a list of Objects

I have a simple action that can be attached to list items in an {{#each}} loop, and when that action is triggered, it will link to that instance of the model.
This is what it looks like now
VpcYeoman.SuperTableController = Ember.ArrayController.extend({
actions: {
goTo: function(input) {
this.transitionToRoute('someModel', input);
}
}
});
The action is called on an HTML element like this
{{action 'goTo' this bubbles=false}}
You can see the problem with this in that 'goTo' cannot be reused on other models because it is specifically looking at the 'someModel' model.
Please help me make this action work for whatever the current model is
I tried replacing 'someModel' with a generic 'model' & even 'this.model' but they didn't work.
Do not reply with 'use {{#link-to}}' please. I am aware that this exists and

Before you read this, you should know that I do recommend you use the link-to helper. I normally pass a computed property to the helper when I need it to change based on the model...
I am not sure where you have that action in your code, but you could just compute that path as needed. For example, take this item controller:
App.ItemController = Ember.ObjectController.extend({
getTransitionPath: function () {
return this.get('foo') + '_bar';
},
transitionPath: function () {
return this.get('foo') + '_bar';
}.property('foo'),
actions: {
goTo: function(input) {
//this.transitionToRoute(this.getTransitionPath(), input); // Regular method
this.transitionToRoute(this.get('transitionPath'), input); // Computed property
}
}
});
I also don't know what kind of logic you are looking for inside of those methods, but this pattern should work on a per model basis.
Good luck!

Update form record for disabled fields

I have a complex form in ExtJS 4, where various parts of the form are dynamically enabled or disabled based on what the user selects from some of the form fields. Whenever I disable a form field, I also clear any value it currently has in it.
I have a model class representing the form. To load the form, I use form.loadRecord(model). To update my model when the user "submits" the form, I use model.set(form.getValues()).
The problem is that ext's getValues() implementation skips form fields that are disabled. This causes problems in my case, because some of form fields that have changed values are disabled (ie. form fields whose values I cleared when I disabled them). As a result, these fields are not updated (cleared) in the model when I call model.set(...).
What would be the best way to work around this problem? I've considered the following ideas, but none seems very good. If you have a better one, I'd like to hear it.
Clear the model (set all fields to undefined) before calling model.setValues(). Unfortunately, there is no model.clear() method, so this gets ugly quickly - I have to get all fields and iterate over them, clearing each one individually.
Clear model fields also when I disable and clear the form fields. This seems to violate separation of concerns and also means the model gets changed, even when the user chooses to cancel and not submit the form.
Override ext's implementation of form.getValues() to not skip disabled fields. This is even more ugly because the actual code that needs to be changed is in the Ext.form.field.Field class, not Ext.form.Basic.

Disabled fields are commonly (not only extjs) always excluded from post data. Instead set fields readonly. The mean difference between readonly and disabled fields is just that.

This is the solution that you exposed in the thrid point:
The only way you have to change this behaviour is override this method.
Ext.override('Ext.form.field.Field', {
getSubmitData: function() {
var me = this,
data = null;
if (!me.isFileUpload()) {
data = {};
data[me.getName()] = '' + me.getValue();
}
return data;
}
});
About your first point, isn´t .reject(false) useful?
The latest option could be override the getSubmitData for every single field in your form as follow:
{
xtype: 'textfield',
getSubmitData: this.getSubmitDataMyOwnVersion
}

I realize this is an old post but I have run into this same issue. IMHO this is a rather serious issue because it can cause data problems without you knowing about it. In my case I also set several check boxes to false when disabled but because of the way this works they were being left as true behind the scenes.
As a work around I now loop through all the fields in the form and manually update the record for each one. It's more work but I don't have to override any classes and the loop is generic enough that it will continue to work if/when the form definition is changed.
var fields = this.getForm().getForm().getFields();
var record = this.getForm().getRecord();
for (var i = 0; i < fields.length; i++) {
var name = fields.items[i].name;
var value = fields.items[i].value;
record.set(name, value);
}

Note that Mark Wagoner's answer breaks any advanced components / features of other components since it takes the value directly rather then getting the getSubmitValue(). I had to slightly modify Iontivero's answer as that was not the class I found Extjs calling at least in 4.2.0.
Ext.define('YourAppName.override.Field', {
override: 'Ext.form.field.Base',
getSubmitData: function() {
var me = this,
data = null,
val;
if (me.submitValue && !me.isFileUpload()) {
val = me.getSubmitValue();
if (val !== null) {
data = {};
data[me.getName()] = val;
}
}
return data;
}
});
then in Ext.application:
requires: ['YourAppName.override.Field'],

I haven't encountered that problem so far, but I update my model using the update() method rather than the setValue(). Maybe it handles disabled fields differently? Or maybe I'm headed down a path to need this answer as well since we're just starting major testing? -- This is the basic usage of the Form.update method though, assuming form is an Ext.form.Panel and this.record is a model instance:
//Save record
form.updateRecord(this.record);
this.record.save();
this.record.commit();
If that doesn't work for you, I would suggest writing a similarly named method and extending the form panel to include it that gets the array of values then goes through each one and updates it only if it's not null.