CODEWITHSUNDEEP
flowtype
kdojeteri
kdojeteri

Reputation: 805

Declare a polymorphic class that extends another polymorphic class

I'm writing a component in React that expects to receive a component, that owns a specific field onPropChange to be accessed via a ref, as a prop. 

/* @flow */
import * as React from 'react';

type onPropChangeObject<Props> = {
    [key: $Keys<Props>]: (newValue: any) => void
}

declare class PropWatchableComponent<DefaultProps, Props: Object, State> 
    extends React.Component<DefaultProps, Props, State> 
{
    onPropChange?: onPropChangeObject<Props>;
}

But the type checking fails with multiple errors in the latest version of Flow (0.39.0) as seen here

8: declare class PropWatchableComponent<DefaultProps, Props: Object, State> extends React.Component<DefaultProps, Props, State> {   ^ undefined. Did you forget to declare some incompatible instantiation of `DefaultProps`?. This type is incompatible with
8: declare class PropWatchableComponent<DefaultProps, Props: Object, State> extends React.Component<DefaultProps, Props, State> {   ^ some incompatible instantiation of `DefaultProps`
8: declare class PropWatchableComponent<DefaultProps, Props: Object, State> extends React.Component<DefaultProps, Props, State> {   ^ undefined. Did you forget to declare some incompatible instantiation of `State`?. This type is incompatible with
8: declare class PropWatchableComponent<DefaultProps, Props: Object, State> extends React.Component<DefaultProps, Props, State> {   ^ some incompatible instantiation of `State`
8: declare class PropWatchableComponent<DefaultProps, Props: Object, State> extends React.Component<DefaultProps, Props, State> {
                                        ^ DefaultProps. This type is incompatible with
8: declare class PropWatchableComponent<DefaultProps, Props: Object, State> extends React.Component<DefaultProps, Props, State> {
                                        ^ undefined. Did you forget to declare DefaultProps?
8: declare class PropWatchableComponent<DefaultProps, Props: Object, State> extends React.Component<DefaultProps, Props, State> {
                                                                     ^ State. This type is incompatible with
8: declare class PropWatchableComponent<DefaultProps, Props: Object, State> extends React.Component<DefaultProps, Props, State> {
                                                                     ^ undefined. Did you forget to declare State?

What's all this talk about undefined? I'm clearly declaring both DefaultProps and State as type parameters. What did I forget?

Upvotes: 1

Views: 373

Answers (1)

jukben
jukben

Reputation: 1098

see this, you should use interface instead `class'.

https://flowtype.org/try/#0PQKgBAAgZgNg9gdzCYAoAlgWwA5wE4AuYASgKYCGAxkVHnJmAOR4XWMDcqqBAntqWDgA7AAp1sAYQAW5IQHNSAeQBGAK1LUAPGLjYAzgC4wK9dQB8YALxgA3qjBgA2gGtSPIwBIA0m73bxemYAukYAFEKkCABq5DAArqRGsjwAlFYWAG5w6AAmqAC+XOhCBKR4UFQCOtgA6uQElDLKMKQS9LgRJf66hsZqGgQWdg4AkNgBRtV6nA72DoKi4tKyCgD8RsLVy-JK-VpTZpyF86hQcULU6MJgCPWNWzI7eqE1eOTY-DlGEjDken7VOoNJotNo4YSkLomAZmMxpGyFVCUX7-MAAZVucjBHUhRFIAA9SkIcnoSKwCAA6bEQkq2OabJaPBQbRa6bYKaFaTmDKx00bjXRhchpSwWSjCPRwFoU+ByUKMKgEK5CRgAGjAwrmhURt2BDxWpGeGPIWPaNIIKSAA

Upvotes: 1

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