ng-option with null value causes empty selection
  • 22-May-2023
Lightrun Team
Author Lightrun Team
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ng-option with null value causes empty selection

ng-option with null value causes empty selection

Lightrun Team
Lightrun Team
22-May-2023

Explanation of the problem

Bug Description: In a specific use case, there is a bug where an option with a null value fails to display as selected when using an ng-select component. When the model’s value is null, the selection appears empty instead of showing the desired option.

Steps to Reproduce: To reproduce this issue, follow these steps:

  1. Implement an ng-select component with the following attributes:
    • Bind the ngModel directive to the “dimensionalFilters.campaign” property.
    • Attach the “generateReport()” method to the ngModelChange event.
    • Set the [clearable] attribute to “false”.
  2. Within the ng-select component, define the following ng-option elements:
    • Create an ng-option element with [value] set to null and the inner text as “Show All”.
    • Iterate over the “campaigns” array using *ngFor directive, and for each item “c”, create an ng-option element with [value] set to “c.id” and the inner text as “{{ c.name }}”.

Actual Behavior: When the option with null value is selected, the model is populated with an object having the properties {$ngOptionValue: null, $ngOptionLabel: “Show All”, disabled: false}. However, the “Show All” option does not appear as selected, and the model’s value remains null.

Expected Behavior: The “Show All” option should be displayed as selected, and the model’s value should be set to null upon selecting this option.

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Problem solution for ng-option with null value causes empty selection

The behavior under scrutiny has sparked a contentious debate within the technical community, with varying opinions regarding its classification as a bug or a deliberate design choice. Advocates for bug fixing emphasize the importance of addressing issues that deviate from expected behavior. They argue that the current behavior, where selecting the null option does not display as expected and the model’s value remains null, is inconsistent and could lead to confusion for users. From their perspective, rectifying this behavior would enhance the overall user experience and align with conventional expectations for selecting null options.

On the other side of the discussion, some view the call for change as an unjustified critique, attributing it to an individual’s admission of incompetence or an attempt to rationalize laziness. They contend that treating null and undefined values as indicative of an empty or cleared state is a deliberate decision within the system’s design. Introducing modifications without thorough consideration of potential ramifications could introduce unintended consequences and break existing functionality. As a possible solution, they propose using a distinct value, such as -1, to represent the desired null state, allowing the existing treatment of null and undefined values to be preserved while still achieving the desired behavior.

In evaluating the appropriate course of action, it is crucial to carefully assess the potential impact of any changes. One approach to manage changes effectively is through the use of major version releases, which allow for breaking changes while ensuring backward compatibility for existing codebases. Additionally, comprehensive testing plays a vital role in identifying and mitigating potential disruptions caused by modifications. Prioritizing system stability and avoiding unintended consequences are essential factors in decision-making. Ultimately, the resolution should strike a balance between addressing user concerns, adhering to expected behavior, and maintaining the overall stability and functionality of the system.

  1. Current ng-select Component Implementation:
<ng-select [(ngModel)]="dimensionalFilters.campaign" (ngModelChange)="generateReport()" [clearable]="false">
  <ng-option [value]="null">Show All</ng-option>
  <ng-option *ngFor="let c of campaigns" [value]="c.id">{{ c.name }}</ng-option>
</ng-select>


  1. Proposed Implementation Using -1 as Null State:
items = [
  { label: 'Select all', value: -1 },
  { label: 'One', value: 1 }
]

onChange(value) {
  if (value === -1) {
    // Treat the same as with null.
  }
}

Other popular problems with ng-select

Problem: ng-select not showing selected value in input field

One of the most common issues faced while using ng-select is that the selected value does not show up in the input field. This can happen when there is an issue with the bindings or when the options list is not correctly populated. This issue can be frustrating for users as they might think that the selection has not been made.

Solution:

To solve this issue, the first thing to check is whether the selected value is correctly bound to the ng-model property. If the binding is correct, then check if the options list is correctly populated. Also, ensure that the labelField property is correctly set in the ng-select component. If all these checks are done correctly, then the selected value should show up in the input field.

Problem: ng-select dropdown not opening or closing

Another common issue with ng-select is that the dropdown does not open or close when clicked. This issue can occur due to a variety of reasons such as incorrect configuration, incorrect bindings or incorrect use of events.

Solution:

The first thing to check is the configuration of the ng-select component. Ensure that the dropdown position and size are correctly set. If this does not solve the issue, check the bindings of the component to ensure that the options list and selected value are correctly bound. Another possible issue could be the use of events. If the dropdown is not opening or closing, check if the events such as (click) and (focus) are correctly used.

Problem: ng-select options not filtered correctly

ng-select allows filtering of options by setting the searchFilter property. However, sometimes the filtering does not work as expected, and all the options are displayed even when there is a filter applied.

Solution:

The first thing to check is whether the searchFilter function is correctly implemented. Check if the function is returning the correct values based on the filter applied. Another possible issue could be that the options list is not correctly populated. Ensure that the options list contains the correct data and that the labelField and valueField properties are correctly set. If all these checks are done correctly, then the filtering of options should work as expected.

A brief introduction to ng-select

ng-select is a powerful and flexible Angular component that provides a user-friendly and intuitive dropdown list selection interface. The component is built with flexibility and customization in mind, and it comes with a wide range of features that make it easy to integrate into any Angular application. ng-select is built on top of Angular Forms, and it provides support for data binding, filtering, and searching, as well as customizable templates and themes.

One of the core strengths of ng-select is its flexibility and ease of use. The component is designed to work seamlessly with Angular Forms, and it provides a range of options for data binding and event handling. ng-select also comes with a range of pre-built templates and themes, which can be easily customized to match the design and layout of any application. In addition, ng-select is highly configurable, and it provides a range of options for customizing its behavior, including the ability to limit the number of items displayed in the dropdown list, enable/disable search, and much more.

Overall, ng-select is a powerful and flexible Angular component that provides a range of features and options for building dropdown lists and select interfaces in Angular applications. The component is designed to be highly configurable and customizable, and it comes with a wide range of pre-built templates and themes that can be easily adapted to match the design and layout of any application. Whether you are building a small single-page app or a complex enterprise-level application, ng-select provides a flexible and intuitive interface for selecting and filtering data.

 

Most popular use cases for ng-select

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