Can you clarify the significance of 'as' when it comes to assigning a class?

I searched Google and looked through the Angular documentation, but couldn't find an explanation for what I'm encountering.

Can anyone clarify what the "as" keyword means? And can you point out any mistakes in my code below?

I have component A being used in component B, where a variable is declared in B with 'as' A. I am trying to access a function from A, but I'm getting an error because the function doesn't seem to exist.

A.component.ts;

...

getValue ():Array<string> {
 return this.filter( elm => elm.length > 5 );
}

...

B.component.ts;

...

type C = A;

...

public coolArr: C;

printArr(param: any):void{
 coolArr = param as A;
 console.log(coolArr.getValue);
}

...

I'm unsure of where I went wrong in my implementation.

Answer №1

Your function:

displayArray(parameter: any):void

This function is designed to accept any type of parameter, whether it be null, an object, an array, or anything else. However, it is not recommended to use any in your TypeScript code as it can lead to unexpected errors. It's always better to specify the proper types.

specificArray = parameter as SpecificType;

By using this line of code, you are informing the TypeScript compiler that the parameter should be treated as type SpecificType. Essentially, you are overriding the compiler's default behavior and asserting that you are certain the parameter will conform to SpecificType. This validation occurs during compile-time.

The issue you are encountering now is a run-time problem. While you have specified specificArray as SpecificType, it may still hold an arbitrary value at runtime, which could cause unexpected behavior when trying to reference it later on.

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