Adding items

Learn to add items with the addItem function.

Adding items (add)

cart.add(...) adds a product to the cart. Each call puts one item at the end of the list.

val cart = mutableListOf<Product>()
cart.add(Product("Apple", 5.0))
cart.add(Product("Bread", 3.0))
println(cart.size)  // 2

After two items, cart.size is 2. mutableListOf is a dynamic list; you don't need to know the item count in advance.

Product("Apple", 5.0) creates a new Product instance and adds it to the list.

The cart.size property

cart.size gives the number of items in the cart. For an empty cart it returns 0.

val cart = mutableListOf<Product>()
println(cart.size)  // 0
cart.add(Product("Apple", 5.0))
println(cart.size)  // 1

Each add call increases the size by one. size is a property; no parentheses needed.

The size grows with each item you add; there is no fixed limit.

Exercise Add two items and print the size

Add two items to the cart from the previous lesson. Add cart.add(Product("Apple", 5.0)) and cart.add(Product("Bread", 3.0)) before println(cart.size). The size should be 2.

Show example solution

data class Product(val name: String, val price: Double)

fun main() {
    val cart = mutableListOf<Product>()
    cart.add(Product("Apple", 5.0))
    cart.add(Product("Bread", 3.0))
    println(cart.size)
}

Test yourself

Match the list methods

cart.add(item)

Add an item
cart.size

Item count
mutableListOf

Empty list
Product(...)

New product
What does cart.add(Product("Apple", 5.0)) do?
- Removes Apple from the cart
- Shows Apple
- Empties the cart
- Adds Apple to the cart
Show answer

Adds Apple to the cart — add puts a new Product in the list.

Complete the add call

cart.____(Product("Apple", 5.0))

Show answer

cart.add(Product("Apple", 5.0))

Next lesson: Calculating totals

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