Adding items

Learn to add items with the addItem method.

The addItem method

To add a product to the cart we will write the addItem method. This method takes name and price parameters and appends them to the names and prices lists. The method returns no value; its return type is void.

To append an element to a list you use the .add() method: names.add(name);. Keeping the two lists parallel matters: the i-th element of names should have its price as the i-th element of prices. So addItem appends to both.

List.add

The List.add(x) method appends element x to the end of the list. It mutates the original list; it does not return a new list. For example after names.add("Notebook"); the list names has "Notebook" at the end.

Consistency matters with parallel lists: addItem appends to both names and prices. If you append to only one, the lists end up with different lengths and printCart breaks. Practical tip: always append to parallel lists together.

Exercise Write the addItem method

Add an addItem method to the Cart class. Its signature is void addItem(String name, double price). In the body append to both lists with names.add(name); and prices.add(price);. main already adds two products and prints item added. The output on a single line must be item added.

Show example solution

class Cart {
  List<String> names = [];
  List<double> prices = [];

  void addItem(String name, double price) {
    names.add(name);
    prices.add(price);
  }
}

void main() {
  var cart = Cart();
  cart.addItem("Notebook", 25.0);
  cart.addItem("Pen", 10.0);
  print("item added");
}

Test yourself

Write the addItem body

void addItem(String name, double price) {
  ____
}

Show answer

void addItem(String name, double price) {
  names.add(name); prices.add(price);
}

What does the addItem method do?
```
cart.addItem("Notebook", 25.0);
```
- Removes a product
- Computes the total
- Prints the cart
- Adds a product to the cart
Show answer

Adds a product to the cart — addItem adds a new product to the cart.
Match each part to its job

void addItem

Method declaration
String name

Name parameter
double price

Price parameter
names.add(name)

List append

Next lesson: Calculating totals

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