Dart For Loop
Repeating code with precision and control
🔁 What is For Loop?
For loops repeat code a specific number of times. They're perfect when you know exactly how many iterations you need, like counting from 1 to 10 or processing items in a list.
// Simple for loop example
void main() {
for (int i = 1; i <= 5; i++) {
print('Count: $i');
}
print('Loop finished!');
}
Types of For Loops
Traditional For
Classic loop with counter variable
for (int i = 0; i < 5; i++) {
print(i);
}For-in Loop
Iterate through collections
for (String name in names) {
print(name);
}For-each Method
Functional approach to iteration
numbers.forEach((num) {
print(num);
});Nested Loops
Loops inside other loops
for (int i = 0; i < 3; i++) {
for (int j = 0; j < 3; j++) {
print('$i,$j');
}
}🔹 Basic For Loop
The traditional for loop has three parts: initialization, condition, and increment:
void main() {
// for (initialization; condition; increment)
for (int i = 1; i <= 5; i++) {
print('Number: $i');
}
}Output:
Number: 1
Number: 2
Number: 3
Number: 4
Number: 5
🔹 For-in Loop
Iterate through lists, sets, or any iterable collection:
void main() {
List fruits = ['Apple', 'Banana', 'Orange', 'Mango'];
print('My favorite fruits:');
for (String fruit in fruits) {
print('- $fruit');
}
} Output:
My favorite fruits:
- Apple
- Banana
- Orange
- Mango
🔹 Loop with Index
Access both index and value when iterating:
void main() {
List colors = ['Red', 'Green', 'Blue'];
// Method 1: Traditional for loop
for (int i = 0; i < colors.length; i++) {
print('${i + 1}. ${colors[i]}');
}
print('---');
// Method 2: Using asMap()
colors.asMap().forEach((index, color) {
print('${index + 1}. $color');
});
} Output:
1. Red
2. Green
3. Blue
---
1. Red
2. Green
3. Blue
🔹 Nested For Loops
Use loops inside other loops for multi-dimensional operations:
void main() {
print('Multiplication Table (1-3):');
for (int i = 1; i <= 3; i++) {
for (int j = 1; j <= 3; j++) {
int result = i * j;
print('$i × $j = $result');
}
print('---'); // Separator between tables
}
}Output:
Multiplication Table (1-3):
1 × 1 = 1
1 × 2 = 2
1 × 3 = 3
---
2 × 1 = 2
2 × 2 = 4
2 × 3 = 6
---
3 × 1 = 3
3 × 2 = 6
3 × 3 = 9
---
🔹 Loop Control Statements
Control loop execution with break and continue:
void main() {
print('Numbers 1-10 (skipping 5, stopping at 8):');
for (int i = 1; i <= 10; i++) {
if (i == 5) {
continue; // Skip this iteration
}
if (i == 8) {
break; // Exit the loop
}
print('Number: $i');
}
print('Loop ended');
}Output:
Numbers 1-10 (skipping 5, stopping at 8):
Number: 1
Number: 2
Number: 3
Number: 4
Number: 6
Number: 7
Loop ended
🔹 Practical Examples
Real-world applications of for loops:
🔸 Sum of Numbers
void main() {
int sum = 0;
for (int i = 1; i <= 100; i++) {
sum += i;
}
print('Sum of numbers 1-100: $sum');
}🔸 Finding Even Numbers
void main() {
List evenNumbers = [];
for (int i = 1; i <= 20; i++) {
if (i % 2 == 0) {
evenNumbers.add(i);
}
}
print('Even numbers 1-20: $evenNumbers');
}