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Mattijs
Mattijs

Reputation: 66

Flow: accept multiple types as function arguments

I’m trying to get function c to accept two types. The types are the same except for the optional id property in Foo. Flow errors on this even if I check for the existence of id before using it. I tried searching here and in the docs but I couldn’t find anything.

type Foo = {
  bar: string,
  id?: string,
}

type Bar = {
  bar: string,
};

const a = (args: Bar) => {
  b(args);
}

const c = (args: Foo) => {
  b(args);
}

const b = ({ bar, id }: Bar | Foo) => {
  // As soon as you use id here Flow errors out, even though id is optional
  // and I check for it’s existence.
  if (id) {
    console.log(id);
  }
}

View a working example on Try Flow

Upvotes: 1

Views: 491

Answers (1)

Dave Meehan
Dave Meehan

Reputation: 3201

Flow currently (v0.69) has some weaknesses over object destructuring, you can achieve what you want without destructuring:

const b = (obj: Bar | Foo) => {
  if (obj.id) {
    console.log(obj.id)
  }
}

Upvotes: 1

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