Listing the cart

Write the method that prints the cart formatted.

Listing the cart

To print the products in the cart we will write a printCart method. This method walks the names and prices lists by index and writes each product on a single line.

To walk by index we use a classic for loop: for (var i = 0; i < names.length; i++). On each iteration i goes from 0 to names.length - 1. With names[i] and prices[i] we reach the i-th elements of the parallel lists.

Formatted output

In printCart, while each product is written on a single line, name and price are separated by a space. print("${names[i]} ${prices[i]}"); uses interpolation to embed both fields into one string and ends with a new line.

Commas or dashes could be used instead; the formatting choice is yours. In this project we use spaces. Writing two fields on one line lets you scan the cart quickly. The ${names[i]} braced interpolation is required to embed an expression (index access).

Exercise Write the printCart method

Add a printCart method to the Cart class. Its signature is void printCart(). In the body walk indices with for (var i = 0; i < names.length; i++) and print with print("${names[i]} ${prices[i]}");. main already adds two products and calls printCart. The output must be two lines: Notebook 25.0 and Pen 10.0.

Show example solution

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

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

  double getSubtotal() {
    double sum = 0;
    for (var p in prices) {
      sum += p;
    }
    return sum;
  }

  void printCart() {
    for (var i = 0; i < names.length; i++) {
      print("${names[i]} ${prices[i]}");
    }
  }
}

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

Test yourself

What does the printCart method do?
```
cart.printCart();
```
- Computes the total
- Prints the cart to the screen
- Removes a product
- Adds a product
Show answer

Prints the cart to the screen — printCart writes the products in the cart to the screen.
Match each part to its job

names.length

Element count
names[i]

I-th name
prices[i]

I-th price
print(...)

Prints to screen

Write the print line

void printCart() {
  for (var i = 0; i < names.length; i++) {
    print(____);
  }
}

Show answer

void printCart() {
  for (var i = 0; i < names.length; i++) {
    print("${names[i]} ${prices[i]}");
  }
}

Next lesson: Putting it together

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