Typescript Array of Array of Array of Objects

Question

I have a curriculum that doesn’t need to be changed dynamically so I want to hard code it in service in my angular project.

The data is as follows:

Term 1 Term 2 Term 3

Each term has 5 grades Each grade has 10 subjects Each subject has 12-16 weeks depending on the term.

I want to access the data as follow

currentLesson = term.grade.subject.week.data;

To do this, I believe I need to make a Term Array which each term consists of a grade array which then each grade consists of a subject Array which then each subject Array consists of An object of week / curriculumData.

I can make the last simple Array of objects but my mind shuts down trying to do the array of Array of Array of objects.

Or is there a better way to achieve this?

I'm assuming you really mean something like const currentLesson = curriculum.terms[t].grades[g].subjects[s].weeks[w].data where t,g,s, and w are numbers. But what are you asking here... how to define interfaces for these types? Or how to convert your curriculum data into this format? Or something else? — jcalz
– jcalz, Commented Aug 4, 2019 at 3:09
Thanks for the reply! In short, I don’t know how to declare an array of arrays of arrays of objects. — MattyO
– MattyO, Commented Aug 4, 2019 at 3:58
Right now my declaration looks like this but I’m not confident that it’s the best approach. interface curriculum { term: number; grade: Array<{ id: number; subject: Array<{ id: number; week: Array<{ id: number; data: string; }> }> }> } — MattyO
– MattyO, Commented Aug 4, 2019 at 4:18

Martin Poelstra · Accepted Answer · 2019-08-04 13:03:51Z

2

If all of your 'data' is a simple string, you could simply create a multidimensional array like this:

const lessons: string[][][][] = buildLessons();
const currentLesson = lessons[t][g][s][w];

Of course, you could replace string with a more complicated datatype if you wanted to, e.g.:

interface Lesson {
  data: string;
  otherProperty: number;
}
const lessons: Lesson[][][][] = buildLessons();
const currentLesson = lessons[t][g][s][w];
// do something with currentLesson.data, etc

Alternatively, if you want to use an object structure, you could also write that out in a more readable way by splitting into separate interfaces, like so:

interface Curriculum {
  term: number;
  grades: Grade[];
} 

interface Grade {
  id: number;
  subjects: Subject[];
}

interface Subject {
  id: number;
  weeks: Week[];
}

interface Week {
  id: number;
  data: string;
}

let example: Curriculum;
const currentLesson = example.grades[g].subjects[s].weeks[w].data;

answered Aug 4, 2019 at 13:03

Martin Poelstra

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2 Comments

MattyO Over a year ago

The splitting interfaces is what I was after. Thanks so much!

Martin Poelstra Over a year ago

You're welcome :) In that case can you please accept the answer?

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