Implementing circular generic in Typescript tutorial

Question

Implementing circular generic in Typescript tutorial

I have a question regarding the code snippet below:

interface BaseProps<TControl> {
  onEvent: (control: TControl) => void;
}

class BaseControl<TValue, BaseProps<any>> {
  onBlur = () => {
    onEvent(this); //subscriber must see the whole TS-class instead of BaseControl<TValue, BaseProps<any>>
  }
}

It seems that defining a class like:

class BaseControl<TValue, BaseProps<this>>> {}

or having an infinite structure like:

class BaseControl<TValue, BaseProps<BaseControl<TValue, BaseProps<...etc.>>>> {}

is not viable. Is there a way to achieve a similar concept to a generic pointer, such as using BaseProps<this>?

typescript typescript-generics circular-reference self-reference

Answer 1

Answer №1

When dealing with type variables in a class, it's important to understand their limitations and how to properly reference them. The example below illustrates this concept:

class Foo<T> { }

In this scenario, T represents a type variable, meaning it cannot function as a type on its own. This restricts certain syntax possibilities, as shown in the following examples:

interface Foo<T> { } // valid
class Bar<any> { } // error: type variable cannot be 'any'
class Baz<Foo<any> { } // error: type variable cannot be 'Foo<any>'

It's crucial to note that attempting to use type variables incorrectly can lead to errors. Instead, focus on utilizing the type of this within the class itself, as demonstrated below:

class Foo<T> {
    foo: Foo<T>;
    constructor(foo: Foo<T>) {
        this.foo = foo;
    }
}

If you need further assistance, please provide more clarity in your question. It appears you may be facing an XY problem, but the suggested approach should help resolve the issue.

Answer 2

When dealing with type variables in a class, it's important to understand their limitations and how to properly reference them. The example below illustrates this concept:

class Foo<T> { }

In this scenario, T represents a type variable, meaning it cannot function as a type on its own. This restricts certain syntax possibilities, as shown in the following examples:

interface Foo<T> { } // valid
class Bar<any> { } // error: type variable cannot be 'any'
class Baz<Foo<any> { } // error: type variable cannot be 'Foo<any>'

It's crucial to note that attempting to use type variables incorrectly can lead to errors. Instead, focus on utilizing the type of this within the class itself, as demonstrated below:

class Foo<T> {
    foo: Foo<T>;
    constructor(foo: Foo<T>) {
        this.foo = foo;
    }
}

If you need further assistance, please provide more clarity in your question. It appears you may be facing an XY problem, but the suggested approach should help resolve the issue.

Implementing circular generic in Typescript tutorial

Answer №1

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