Question model

Design question, option, and answer types.

What is a question model?

In a quiz app, the question model is designed first. A question consists of text, options, and the index of the correct answer. In TypeScript you define this structure with an interface. This way all questions share the same shape and missing fields are caught at compile time.

interface Question {
  text: string;
  options: string[];
  correctIndex: number;
}

Answer and option types

Beside the question model, answer and option types are also defined. Options are a string[] array; the user's answer is the index of the chosen option, i.e. a number. This separation keeps each part of the model with a single responsibility.

type Answer = number;  // chosen option index
type Option = string;   // an option text

Exercise Create a question object

Define a Soru interface: metin: string, siklar: string[], dogruIndex: number. Create a Soru object named s1 with text "TS nedir?", options ["dil", "renk", "araç"], and correct index 0. Print s1.metin with console.log.

Show example solution

interface Soru {
  metin: string;
  siklar: string[];
  dogruIndex: number;
}
const s1: Soru = {
  metin: "TS nedir?",
  siklar: ["dil", "renk", "araç"],
  dogruIndex: 0
};
console.log(s1.metin);

Test yourself

What type should the dogruIndex field be in a Soru interface?
- number
- string
- boolean
- string[]
Show answer

number — Since the index of the correct answer is a number, the dogruIndex field is defined as number.

Question interface keyword

 ____ Soru {
  metin: string;
  siklar: string[];
  dogruIndex: number;
}

Show answer

 interface Soru {
  metin: string;
  siklar: string[];
  dogruIndex: number;
}

Question model parts

metin

Question text
siklar

Options array
dogruIndex

Correct answer index
Cevap

Chosen option number

Next lesson: Question pool

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