Angular Errors | Generated by AI

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When working with Angular, developers often encounter specific exceptions and errors. Below is a categorized list of common issues, their causes, and solutions:

Template & Data Binding Errors

  1. ExpressionChangedAfterItHasBeenCheckedError
    • Cause: Changing component data after Angular’s change detection cycle (e.g., in ngAfterViewInit or ngOnChanges).
    • Fix: Use ChangeDetectorRef.detectChanges() or ensure data changes occur before change detection completes.
  2. Cannot read property 'X' of undefined
    • Cause: Accessing uninitialized object properties in templates (e.g., `` when user is null).
    • Fix: Use the safe navigation operator (``) or initialize objects properly.
  3. Can't bind to 'X' since it isn't a known property of 'Y'
    • Cause: Missing component/directive declaration or typo in property name.
    • Fix: Import the directive/component into the module or check for typos.

Dependency Injection (DI) Errors

  1. NullInjectorError: No provider for XService
    • Cause: Service not provided in module/component or circular dependency.
    • Fix: Add the service to the providers array of the module/component.
  2. No value accessor for form control
    • Cause: Custom form control missing ControlValueAccessor implementation or incorrect formControlName binding.
    • Fix: Implement ControlValueAccessor for custom controls or check form bindings.

TypeScript & Build Errors

  1. Type 'X' is not assignable to type 'Y'
    • Cause: Type mismatches (e.g., wrong data type passed to a component).
    • Fix: Ensure types align or use type assertions (if intentional).
  2. ERROR in Cannot find module 'X'
    • Cause: Missing npm package or incorrect import path.
    • Fix: Install the package (npm install X) or correct the import path.

Component & Module Errors

  1. Component is not part of any NgModule
    • Cause: Component not declared in a module or module not imported.
    • Fix: Add the component to declarations in its module or import the module.
  2. ViewDestroyedError: Attempt to use a destroyed view
    • Cause: Subscriptions or async operations running after component destruction.
    • Fix: Unsubscribe in ngOnDestroy or use the async pipe.

HTTP & API Errors

  1. HttpClient provider not found
    • Cause: Missing HttpClientModule import in the module.
    • Fix: Import HttpClientModule in AppModule.
  2. CORS Issues
    • Cause: Backend not allowing requests from the frontend origin.
    • Fix: Configure CORS on the server or use a proxy in Angular (proxy.conf.json).

Routing Errors

  1. Route not found
    • Cause: Incorrect route definition or missing lazy-loaded module.
    • Fix: Check route paths and lazy-load syntax (loadChildren: () => import(...)).

Form Errors

  1. FormControl not found
    • Cause: Using formControlName without wrapping in a [formGroup].
    • Fix: Ensure the parent form group is initialized and bound.

Miscellaneous

  1. Maximum call stack size exceeded
    • Cause: Recursive functions or circular dependencies.
    • Fix: Refactor code to eliminate recursion/circular references.
  2. Zone.js Promise rejection
    • Cause: Unhandled promise rejections.
    • Fix: Add .catch() or use try/catch with async/await.
  3. AOT Compilation Errors
    • Cause: Template syntax incompatible with Ahead-of-Time compilation.
    • Fix: Avoid complex expressions in templates or use Angular-compatible syntax.

Best Practices to Avoid Errors

By addressing these common issues methodically, you can streamline Angular development and reduce debugging time.

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