Summary - Generics

Write a type-safe store class with generics.

Summary - Generics

Generics let a single piece of code work with different types type-safely by parameterizing the type. Generic functions are written as function ad<T>, generic classes as class Ad<T>. Multiple type parameters are also possible: <K, V>. Combining these three forms, you can build type-safe stores, mappers, and collections.

class Eslestirme<K, V> {
  private veri: [K, V][] = [];
  koy(k: K, v: V) { this.veri.push([k, v]); }
}

Exercise Type-safe mapper

Write a generic class Eslestirme<K, V>. It should have a private field veri: [K, V][] starting as an empty array. Method koy(k: K, v: V): void pushes the pair. Method al(k: K): V | undefined returns the matching value, or undefined. Then create an Eslestirme<string, number>, add "a"->1 and "b"->2, and print al("a") and al("b") on separate lines.

Show example solution

class Eslestirme<K, V> {
  private veri: [K, V][] = [];
  koy(k: K, v: V): void {
    this.veri.push([k, v]);
  }
  al(k: K): V | undefined {
    for (let i = 0; i < this.veri.length; i++) {
      if (this.veri[i][0] === k) return this.veri[i][1];
    }
    return undefined;
  }
}
const e = new Eslestirme<string, number>();
e.koy("a", 1);
e.koy("b", 2);
console.log(e.al("a"));
console.log(e.al("b"));

Test yourself

What is the main benefit of generics?
- Type-safe reusable code
- Faster execution
- Shorter variable names
- Less memory usage
Show answer

Type-safe reusable code — Generics let the same code work type-safely with different types. They have nothing to do with speed or memory.

Two-type-parameter store

class Tablo<K, V> {
  private satirlar: [K, V][] = [];
  ekle(k: K, v: V) {
    this.satirlar.push([____]);
  }
}

Show answer

class Tablo<K, V> {
  private satirlar: [K, V][] = [];
  ekle(k: K, v: V) {
    this.satirlar.push([k, v]);
  }
}

Match generic structures

function ad<T>(...)

Generic function
class Ad<T> {...}

Generic class
<T, U>

Multiple type parameters
new Ad<number>()

Instantiation with type argument

Next lesson: extends constraint

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