for-Loops

A for loop repeats a particular block of code multiple times. For example, if we want to check each student's grade in a class of 32 students, we loop from 1 to 32.

The for loop is used to repeat a section of code a known number of times.

Some examples:

Calculate the average age of the school's students. Although you (the programmer) may need help to learn how many students are in the school, the computer can do it. Dart achieves this by using the length property on the List;
Print the even numbers from 1 to 500;
To search in a List of numbers, such as finding the highest score on a test. Again, the computer knows how many grades are in the List, so a for loop is appropriate.

Syntax

Let's look at the syntax of the for loop using the example code below:

The for loop in Dart has three parts:

Initialization: Variable initialization will control the number of loop iterations. In this case, we initialize the variable with name i and with the value 0;
Condition: This is the condition that determines whether to continue iterating the loop. In this case, we check if the value i is less than 5;
Increment or Decrement are the operations performed on the counter at the end of each loop iteration.

Note

It is important to remember that for loops can be infinite if the condition never becomes false. Remember, it is essential to check the condition carefully.

Each of these instructions in the for loop is separated by a semicolon ;.

Example

In this example, we use a for loop to print a message to the console five times. Here's how it works:

main


              12345
            
void main() {
  for (int i = 1; i <= 5; i = i + 1) {
    print("Iteration ${i}");
  }
}

int i = 1 - We initialize a variable i with the value 1. This variable will be used as a counter for iterations;
i <= 5 - We set a condition that specifies the loop should continue as long as i is less than or equal to 5;
i++ - After each iteration, the variable i is incremented by 1;
print("Iteration ${i}") - We print a message to the console, where ${i} represents the value of the iteration counter. In the first iteration, it will be "Iteration 1", in the second iteration, "Iteration 2", and so on.

for-Loop with List

The for loop allows you to work with lists conveniently. Let's look at an example:

main


              123456
            
void main() {
  List<String> fruits = ["apple", "banana", "orange"];
  for (String fruit in fruits) {
    print(fruit);
  }
}

Let's take a closer look at how this program works:

First, we create a List containing three strings that represent different fruits: "apple", "banana", and "orange". This list is stored in the variable fruits.

We use a for loop, which is designed to iterate through each item in the fruits list. Each item in the List will be retrieved one by one and stored in the variable fruit. Here, fruit is a variable that takes the value of each fruit during each iteration.

Within the loop, we print the current fruit, which is stored in the variable fruit, to the console using the print function. Afterward, the code moves on to the next fruit and repeats until all the fruits have been printed to the console.

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Seção 5. Capítulo 4

Introduction to Dart

for-Loops

Syntax

Note

Example

for-Loop with List

What does the syntax of a for loop look like?