Typescript Interface[] vs [Interface]

Question

I am trying to assign an Array of Article to my mongoose document, but it seems Typescript doesn't like that and I don't know why it's showing this warning/error that it's not assignable.

My mongoose Schemas and interfaces (simplified):

interface Profile {
  username: string,
  articles: [Article]
}

interface Article {
  index: number,
  name: string,
}

// Mongoose model
export interface IProfile extends Profile, Document { }
const Article = new Schema({
  index: { type: Number, required: true },
  name: { type: String, required: true },
}, { _id: false })

const Profile = new Schema({
  username: { type: String, index: true },
  upcomingChests: { type: [Article] },
}, { timestamps: true })

export const Profile = model<IProfileModel>('IProfile', Profile)

My code trying to assign Articles:

const profile: Profile = values[0]
const articles: Array<Article> = values[1]
profile.articles = articles // Error/Warning pops up in this line

[ts] Type 'Article[]' is not assignable to type '[Article]'.
Property '0' is missing in type 'Article[]'.

My question:

Why does it say it's not assignable and what's the difference between [Article] and Article[] at all?

Possible duplicate of Type 'Array[]' is not assignable to type '[Array]' — jcalz
– jcalz, Commented Oct 16, 2017 at 14:17

Jokester · Accepted Answer · 2017-10-16 04:59:21Z

2

[Article] means something different: a tuple type with 1 Article element.

You may wanted to use Article[], the same type to Array<Article>.

answered Oct 16, 2017 at 4:59

Jokester

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2 Comments

kentor Over a year ago

So I am supposed to change the interface for Profile so that it says articles: Article[] is that correct?

Jokester Over a year ago

I cannot say much about your actual data, but that should fix type mismatch (and is more likely to be used here).

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