CODEWITHSUNDEEP
javascriptecmascript-6flowtype
Tomas Reimers
Tomas Reimers

Reputation: 3292

Flow Array Generic is Incompatible with Itself?

I'm trying to create an es6 class with flow type checking: 

/* @flow */

export default class ListHolder<Tv> {
  getList = (): Array<Tv> => {
    return [];
  };

  iterateOverList = (): mixed => {
    return this.getList().map((item: mixed, index: number) => {
      // no-op
      return null;
    });
  };
}

The problem is that I keep getting a flow error that Tv [1] is incompatible with Tv [1]. referencing the line getList = (): Array<Tv> => {. Can someone help me understand this error?

It resolves if I comment out the map invocation, but I haven't been able to make much progress beyond that and the error messages aren't particularly helpful.

Thanks,

Upvotes: 0

Views: 89

Answers (1)

Keith
Keith

Reputation: 24241

Looks like your creating a class, but assigning methods to a class is not done using assignment operator. = and arrow functions =>.

I think this is more what your after. ->

/* @flow */


export default class ListHolder<Tv> {
  getList (): Array<Tv> {
    return [];
  };

  iterateOverList (): mixed {
    return this.getList().map((item: mixed, index: number) => {
      // no-op
      return null;
    }); 
  };
}

Upvotes: 1

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