Question 1

How do I add custom validation to ngx-formly?

Accepted Answer

You can define custom validation functions in the field configuration using validators property or create reusable validators by extending Formly's validation system. The docs provide examples for adding async validators or cross-field validation logic.

Question 2

ngx-formly vs building forms manually in Angular?

Accepted Answer

ngx-formly excels for dynamic, configuration-driven forms where JSON schemas reduce code duplication, while manual forms are better for simple, static cases where you need fine-grained control without abstraction overhead. Consider complexity and maintenance needs.

Question 3

Does ngx-formly work with Angular's latest version?

Accepted Answer

Yes, but you must use the compatible version listed in the README's table. For Angular >=18, use @ngx-formly/core@7.x; always check the version guide to avoid dependency conflicts during upgrades.

Question 4

How to conditionally show or hide fields in ngx-formly?

Accepted Answer

Use expressions in the field configuration, such as 'hideExpression' or 'templateOptions', to control visibility based on other field values. The library supports dynamic behavior through hooks and reactive properties for complex conditions.

Question 5

Can I use ngx-formly with JSON Schema?

Accepted Answer

Yes, ngx-formly supports JSON Schema alongside its core schema, allowing you to generate forms directly from standard JSON Schema definitions. This is ideal for backend-driven forms or integrating with API specifications.

Question 6

What's the performance like with large forms in ngx-formly?

Accepted Answer

Performance is generally good due to the reactive forms base, but for very large forms, consider strategies like lazy loading fields or optimizing expressions. The dynamic rendering can add overhead, so profile if you have hundreds of fields.

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