How to define a data type in typescript for arrays?

Question

I am trying to define an array type to basically look like this:

[
  {
    name: string,
    comment: string
  },
  {
    name: string,
    comment: string
  }
]

but it needs to work no matter how many comments there are in the array.

I found some examples with set lengths like this guy How to define array type in typescript?

But I can't get it to work for what I am doing, here is the context:

class Post{
  person: string;
  bird: string;
  content: string;
  image: string;
  comments: Array<MyType>;
  score: number;
  grade: number;
  constructor(p: string, b: string, c: string, i: string = '', cm: Array<MyType> = []) {
    this.person = p
    this.bird = b
    this.content = c
    this.image = i
    this.comments = cm
    this.score = 0
    this.grade = this.score + this.cm.length
  }
}

how should I define the type MyType?

Trash Can · Accepted Answer · 2017-05-21 04:15:09Z

4

class Post{
  person: string;
  bird: string;
  content: string;
  image: string;
  comments: Array<{name:string, comment:string}>;
  score: number;
  grade: number;
  constructor(p: string, b: string, c: string, i: string = '', cm: Array<{name:string, comment:string}> = []) {
    this.person = p
    this.bird = b
    this.content = c
    this.image = i
    this.comments = cm
    this.score = 0
    this.grade = this.score + this.cm.length
  }
}

answered May 21, 2017 at 4:15

Trash Can

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2 Comments

Bird Dad Over a year ago

okay so you only define the types of what will be in the aray not the whole structure of the array?

Trash Can Over a year ago

Yes, that's how you emulate type safety checking in javascript, you just need to tell it the "shape" of the objects your list contains

Aravind · Accepted Answer · 2017-05-21 04:13:42Z

0

I always prefer interface ovre class

interface Post{
  person: string;
  bird: string;
  content: string;
  image: string;
  comments: Array<Comment>;
  score: number;
  grade: number;
}
interface Comment{
    name : string;
    comment:string;
}

answered May 21, 2017 at 4:13

Aravind

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4 Comments

Saravana Over a year ago

I wouldn't convert Post as an interface as the constructor for Post class from the OP has some logic in it. Comment should be fine as an interface though.

Aravind Over a year ago

if you are using models(custom datatype) you can go with the interface. Writing class and creating a instance will trouble some time when instance remains unchanged.

Saravana Over a year ago

The constructor an the logic inside it from the OP implies that Post is not only just to provide structure (where interfaces should be preferred), but also to create an actual instance of Post which you can't with interfaces.

Bird Dad Over a year ago

i just wanted an organized way to create sample data for an angular 4 app i am making, its still not compiling correctly so i decided to just make the api first

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