Type 'myInterface' is not assignable to type 'NgIterable | null

Type ‘myInterface’ is not assignable to type ‘NgIterable | null | undefined’ Angular

When working with Angular, you may encounter the error message “Type ‘myInterface’ is not assignable to type ‘NgIterable | null | undefined’”. This error occurs when you are trying to assign a value of type ‘myInterface’ to a variable or property that expects a value of type ‘NgIterable | null | undefined’.

To understand this error better, let’s break down the types involved:

myInterface: This refers to a custom interface that you have defined in your Angular application.
NgIterable | null | undefined: This is a union type that represents a collection of items or a null/undefined value in Angular.

Now, let’s explore some possible solutions to resolve this error:

Solution 1: Implement the NgIterable Interface

The first solution is to make sure that your custom interface ‘myInterface’ implements the ‘NgIterable’ interface. The ‘NgIterable’ interface provides the necessary methods and properties for iterating over a collection of items in Angular.

Here’s an example of how you can implement the ‘NgIterable’ interface in your ‘myInterface’ interface:


interface myInterface extends NgIterable {
  // Your interface properties and methods here
}

By implementing the ‘NgIterable’ interface, you ensure that your ‘myInterface’ is compatible with the expected type ‘NgIterable | null | undefined’.

Solution 2: Use Type Assertion

If modifying your custom interface is not an option, you can use type assertion to explicitly tell the TypeScript compiler the type of your variable or property. This can be done using the ‘as’ keyword.

Here’s an example of how you can use type assertion to resolve the error:


let myVariable: myInterface = getMyInterface(); // Assuming you have a function that returns 'myInterface'
let iterableVariable: NgIterable | null | undefined = myVariable as NgIterable | null | undefined;

By using type assertion, you inform the TypeScript compiler that ‘myVariable’ should be treated as type ‘NgIterable | null | undefined’, resolving the error.

That’s it! By implementing the ‘NgIterable’ interface or using type assertion, you can resolve the error “Type ‘myInterface’ is not assignable to type ‘NgIterable | null | undefined’”.

Remember to always ensure that the types of your variables and properties match the expected types to avoid such errors in your Angular application.

Type ‘myInterface’ is not assignable to type ‘NgIterable | null | undefined’ Angular