Скачать или смотреть Understanding Why *ngStyle Makes Visualization Disappear in Angular

Discover the solution to the problem of invisible elements when using `*ngStyle` in Angular. Learn how to properly implement `ngStyle` for successful rendering of item components.
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This video is based on the question https://stackoverflow.com/q/63014155/ asked by the user 'greenfield' ( https://stackoverflow.com/u/10348356/ ) and on the answer https://stackoverflow.com/a/63014262/ provided by the user 'Michael D' ( https://stackoverflow.com/u/6513921/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Why Does *ngStyle Make Visualization Disappear in Angular?

If you've ever encountered the confusing scenario where your beautifully crafted Angular component appears to vanish when using the *ngStyle directive, you're not alone. Many developers face this issue, and understanding why it occurs can save you time and frustration. In this guide, we're going to dissect the problem, explore the reasons behind it, and guide you to an effective solution.

The Problem Explained

When building a list component in Angular to display various items, you might leverage the *ngFor directive to iterate through each item. Let’s say you have a structure that looks something like this:

[[See Video to Reveal this Text or Code Snippet]]

While your data correctly renders, the moment you introduce the *ngStyle directive, the items become invisible — you see them in inspect mode, but they don't show on the screen. This is a common issue that can arise due to an incorrect use of syntax within the directive.

Analyzing the Cause

The primary issue here is rooted in how Angular interprets the directives. Using *ngStyle in the example above triggers Angular's structural directive. This can interfere with local styles applied to the component, leading to the unintended outcome of the items being invisible.

Key Points That May Lead to Disappearance:

Structural vs Property Directives: *ngStyle is a structural directive, while ngStyle is a property binding. The asterisk (*) introduction can radically change how components are rendered.

Opacity Control: If your object.booleanValue is false, opacity is set to 0.5, but without proper implementation, it could lead to visibility issues.

The Solution: Proper Syntax

To resolve this problem, the solution is quite straightforward. What you need to do is replace *ngStyle with [ngStyle]. By enclosing the ngStyle directive in square brackets, you allow Angular to treat it as a property binding rather than a structural directive. This ensures the styles will apply correctly without compromising the visibility of the elements.

Updated Code Snippet

Here's how your updated HTML should look:

[[See Video to Reveal this Text or Code Snippet]]

Conclusion

By using correctly formatted directives, such as switching from *ngStyle to [ngStyle], you can effectively manage visual properties without losing the content of your Angular components. Keep these tips in mind, and you'll save yourself from countless hours of debugging! If you ever doubt what's affecting visibility in your Angular app, remember to check your directive syntax first.

Happy coding!