NativeScript for Mobile App Development Data Binding and MVVM

Question 1

What pattern does NativeScript natively support for separating UI and business logic?

Accepted Answer

MVVM (Model-View-ViewModel)

Answer

NativeScript is designed around the MVVM pattern where the ViewModel exposes observable data to the View via data binding.

Question 2

Which NativeScript class must a ViewModel extend to support data binding?

Accepted Answer

Observable

Answer

Extending the Observable class gives a ViewModel the `set` and `get` methods and `propertyChange` event needed for data binding.

Question 3

How is two-way data binding expressed in NativeScript XML?

Accepted Answer

{{ property }} with `text` and setting bindingContext

Answer

In plain NativeScript XML, `{{ property }}` in attribute values creates one-way bindings; two-way binding requires explicitly handling the textChange event alongside the bound value.

Question 4

What property on a NativeScript Page sets the data source for binding?

Accepted Answer

bindingContext

Answer

Setting `page.bindingContext` to an Observable object makes its properties available for binding in the page's XML template.

Question 5

What method on an Observable object triggers property change notifications?

Accepted Answer

set(propertyName, value)

Answer

Calling `this.set('propertyName', value)` on an Observable updates the value and fires a propertyChange event that updates bound UI.

NativeScript for Mobile App Development Practice Test

NativeScript for Mobile App Development Practice Test

NativeScript for Mobile App Development Data Binding and MVVM