Cannot read property 'list_ids' of undefined - object

Question

I am new on Typescript and I don't know how to solve a trivial issue I guess.
I've declared a new class, and then I want to assign the values I got from the apiCall. But the problem I've get is:
Cannot read property 'list_ids' of undefined
On my class, I inicializated the object, and if I want to declare it empty, it appears a mistake.
How can I solve this? If I could declare it empty from the beggining and then assign it, it would be great I guess!
Here I post the code of my class:
export class MyClass {
name: string
op: string
field_id: string
comparsion_values: {
values: [
string
],
list_ids: [number]
field_ids: [
string
],
velocities: [
string
],
prices: [
{
amount: 0
currency: string
}
]
}
}
I Inizializate it as: myObjectClass= new myClass;
And the problem appear when I try to do a push in some of my arrays.
Thank you a lot.

Answer 1

Problem 1:
Based on the naming, I assume you intended list_ids, field_ids to be arrays, but currently they are typed as tuples.
Problem 2:
You are not initializing your comparsion_values property. You are simply defining the type for the property.
You can define the type for comparsion_values in an interface (there is nothing wrong with defining it inline, but it looks messy) and initialize it with empty arrays in the constructor like below:
interface ComparisonValues {
values: Array<string>, // Or string[] would work too
list_ids: Array<number>
field_ids: Array<string>,
velocities: Array<string>,
prices: Array<{
amount: number
currency: string
}>
}
export class MyClass {
name: string
op: string
field_id: string
comparsion_values: ComparisonValues
constructor() {
this.comparsion_values = {
values: [],
list_ids: [],
field_ids: [],
velocities: [],
prices: []
}
}
}