Say I have a custom attribute in Aurelia and I put it on two different element.
If I have variable defined in the class called clickWhen: Date;
And if I set that in a method fired from the first element that has the custom attribute (ie `setupDoubleClick).
If a method is fired from the second element that has the custom attribute on it, is this.clickWhen set (because the first instance has set this.clickWhen) or is it still undefined.
(I hope it is the second.)
They are separate instances and they won't affect each other.
Related
I am using tag-based routing with RiotJS. If the tag in the route contains an other tag, it is automatically mounted. Which is great in some cases. But there are cases when I need to pass some options to the tag being mounted, that can't be passed as tag property. I know that this.tags will contain them and I have the means to pass that parameter afterward. But I still am curious if there is a way to stop RiotJS automounting some subtags.
Sounds like you have a design error.
Remember that a tag can contain any classic JS code; you can simply write a logic that populates the tag in any time, way, shape or form. You can also hide it's content via the if condition until it is populated, while it is mounted. You can also hide it in the parent and prevent its mounting in the same manner if you so desire.
Is is possible to emit a synthetic event from a watched property in a way, that will not be checking the listeners (outside of Vue instance) on Vue instance initialization?
I have a situation in which I would like to watch for that synthetic event on a window object and perform a certain action on an object which does not exist at the time the Vue instance is created.
No matter how I try it to go about it I am getting an error:
Cannot read property 'set' of undefined
In my particular case, I want to 'move' the slider handle (I am using noUiSlider library) to a new position whenever the watched property changes - that is, the error message is specific, but my question refers to the generic case - is it possible? And if yes, how to do it?
For the listener to be able to operate on the slider, create the listener when you create the slider. There's no point to creating it before the slider exists.
I am trying to create fully reusable component using Vue.js 2 and single file components, and right now my approach seems to be impossible to realize.
The goal is to create component for creating forms for a complex, nested JSON structure. This structure is supposed to be edited and then sent to the server. The component itself displays a header and submit button but the fields along with their placing is entirely the responsibility of the user of my component. (front-end engineer)
The MyForm component (implementation is not relevant here) is passed the JSON data and url to post them to.
The form is supposed to be reusable by many other users and the contents of the form itself is supposed to be not relevant. It may have a mix of html/inputs/custom components as children.
Let's imagine a simple scenario without data nesting with the following data:
var mymodel={ name : "My name", surname : "My surname" }
And a form i would like to create using my component:
<MyForm :model="mymodel" :url="http://localhost/post">
<div>
<MyTextInput v-model="model.name" label="Name"/>
<MyPanel>
<MyTextInput v-model="model.surname" label="Surname"/>
</MyPanel>
</div>
</MyForm>
Therefore:
MyForm gets passed a model to submit, stores it in data
MyTextInput is a custom component for displaying input with label
Second MyTextInput is the same component but created in another component contained called 'MyPanel' since this field needs to be placed differently.
As we can see there are many problems with passing variables and composition itself:
Composition:
If i put a <slot></slot> in the tempplate of MyForm for displaying the fields it would be compiled in parent scope, therefore all children (including MyTextField) would not have access to the "model"
If i try to use <MyForm inline-template> i cannot automatically display the form header and footer since all content is being replaced. Additionally when using single file components the compiler will look for all components inside the inline-template which means that i would have to import MyTextInput and MyPanel into MyForm which is not practical. I do not know in advance all components that will never end up in my form!
Passing variables:
If i use the variables directly from "model" (in first TextInput) i receive warning that i am modifying a variable from parent and it will be overwritten on next render (but in this case it will not be overwritten since i am INTENTIONALLY modifying the parent)
I cannot pass the model into second MyTextInput without passing it to MyPanel first. Actually i would have to pass it into EVERY custom component in between. And i do not know in advance how many custom components will there be. Which means that i would have to modify the code of every component that would ever be put into MyForm and require users to pass the data for each custom component they include.
If i would try to properly inform the parent about changes i would need to add v-on: event to every textinput and every custom component in between in order for the event to reach MyForm.
As i have said the component was supposed to be simple and easilly reusable. Requiring users of this component to modify code of every child they put into it and requiring them to add v-on: to every component inside does not seem practical.
Is my idea solvable using Vue.js 2.0 ? I have designed the same component before for AngularJS (1.5) and it was working fine and did not require to add modifications to each child of the form.
I've been using a ui framework based on vue 2.0 and you may get some ideas from its implementation. Based on its implementaion and my little experience with it, I think it's the person who uses your framework's responsibility to assemble the form-model. Also, for a form, we can always easily get all the data to be sent by using fields' value props without v-model's help.
The framework's doc on form element may also be helpful but it's currently only available in Chinese except for the code samples.
I suggest you to use Form Input Components using Custom Events to pass variables in your form.
Mutating a prop locally is now considered an anti-pattern, e.g.
declaring a prop a and then set this.a = someOtherValue in the
component. Due to the new rendering mechanism, whenever the parent
component re-renders, the child component's local changes will be
overwritten. In general, in 2.0 you should treat props as immutable.
Most use cases of mutating a prop can be replaced by either a data
property or a computed property.
I have a TextBlock and its Text property is bound to a ViewModel property. The binding is Oneway.
When I change the Text property of the Control from the xaml.cs the binding gets broken. If the binding is TwoWay I don't have this problem but the source property is updated too. Is it possible to have OneWay binding and change the target property value without braking the binding?
I suggest a workaround, like setting the Binding to TwoWay and ignore the update in the property. Something like this:
private string textValue;
public string TextValue
{
get { return textValue; }
set
{
:
}
}
Now the Property can no longer be set by the view.
Although no code is provided, this scenario typically occurs when you have bound a control to a view model and at a later stage your logic tries to update the value in the control programmatically.
You should not try to do this, that is define multiple sources of the value for a control. If you bind the control to a property on the view model, then to update the value in the control you should update the field in the view model.
If you were to set the value of a bound control programmatically at runtime so that it no longer matched the bound object value, when some other event causes the control binding to be re-evaluated, the value that you have provided programmatically would be overwritten again, you could easily end up with a scenario where the value you provided programmatically is never visible to the user.
In this scenario you should either:
Add a new property to the view model, bind this value to the control, then your program logic can set this value equal to the original property when the data is loaded, and updated when you need to
Not use bindings at all, always write to the control programatically that way you tightly control when the value is updated.
There is a workaround to this if you absolutely must have one. if you are using compiled bindings (x:Bind), then because the bindings are compiled it is possible to call SetValue on the bound dependency property at runtime and the previously compiled bindings will still be evaluated. However I advise against exploiting this because it makes your code a lot harder to follow and debug, when bindings are used, we tend not to look for code that directly addresses and sets control values.
I have a view which contains some tabs (TabView).
Initially some tabs are disabled - they should only be enabled when a certain condition is met.
I'd like to implement it in the following way:
Create a TabViewModel which contains a boolean (observable?) property PersonSelected.
Create a TabViewStore
Bind the TabViewStore to the TabView
In my controller I would have an action method (e.g. onPersonSelected) which will should set the PersonSelected property to true.
What is the best way to bind the PersonSelected property to the View?
As my store would only contain on record, I feel that using the is a bit overkill. Can I do this without the store?
You can simply subscribe to the change event of the UI element (checkbox? in your case). Am I missing something?