Make typescript happy with array & non-array in one value

Question

I want to have a array of Payment(s) for every Rent, but I want to be able to pass one or more Payments through the constructor...

I am getting error that says: "Type '(Payment | Payment[])[]' is not assignable..." on the second appearance of this.payment

Code:

class Rent {
  payments: Payment[]
  date: Date

  constructor(date: Date, payment:Payment|Payment[]) {
    this.date = date
    if(payment instanceof Array){
      this.payments = payment
    }else{
      this.payments = [payment]
    }
  }

PS: I am aware that I could always use [Payment] while creating one, but I like to have options

David Sherret · Accepted Answer · 2015-06-28 18:37:24Z

1

payment in the else condition is still Payment|Payment[].

To fix this, check if it's an instance of Payment and remember that someone could pass in null:

class Rent {
    payments: Payment[];
    date: Date;

    constructor(date: Date, payment: Payment|Payment[]) {
        this.date = date;

        if (payment instanceof Array) {
            this.payments = payment;
        } 
        else if (payment instanceof Payment) {
            this.payments = [payment];
        }
        else {
            this.payments = []; // or throw an error here... depends what you want
        }
    }
}

answered Jun 28, 2015 at 18:37

David Sherret

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1 Comment

Akxe Over a year ago

Thanks, wouldn't find this by myself

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