Dart Programming - Loops

At times, certain instructions require repeated execution. Loops are an ideal way to do the same. A loop represents a set of instructions that must be repeated. In a loop’s context, a repetition is termed as an iteration.

The following figure illustrates the classification of loops −

Let’s start the discussion with Definite Loops. A loop whose number of iterations are definite/fixed is termed as a definite loop.

Moving on, let’s now discuss the indefinite loops. An indefinite loop is used when the number of iterations in a loop is indeterminate or unknown. Indefinite loops can be implemented using −

Let us now move on and discuss the Loop Control Statements of Dart.

Using Labels to Control the Flow

A label is simply an identifier followed by a colon (:) that is appped to a statement or a block of code. A label can be used with break and continue to control the flow more precisely.

Line breaks are not allowed between the ‘continue’ or ‘break’ statement and its label name. Also, there should not be any other statement in between a label name and an associated loop.

Example: Label with Break

void main() { 
   outerloop: // This is the label name 
   
   for (var i = 0; i < 5; i++) { 
      print("Innerloop: ${i}"); 
      innerloop: 
      
      for (var j = 0; j < 5; j++) { 
         if (j > 3 ) break ; 
         
         // Quit the innermost loop 
         if (i == 2) break innerloop; 
         
         // Do the same thing 
         if (i == 4) break outerloop; 
         
         // Quit the outer loop 
         print("Innerloop: ${j}"); 
      } 
   } 
}

Innerloop: 0
Innerloop: 0
Innerloop: 1
Innerloop: 2
Innerloop: 3
Innerloop: 1
Innerloop: 0
Innerloop: 1
Innerloop: 2
Innerloop: 3
Innerloop: 2
Innerloop: 3
Innerloop: 0
Innerloop: 1
Innerloop: 2
Innerloop: 3
Innerloop: 4

void main() { 
   outerloop: // This is the label name 
   
   for (var i = 0; i < 3; i++) { 
      print("Outerloop:${i}"); 
      
      for (var j = 0; j < 5; j++) { 
         if (j == 3){ 
            continue outerloop; 
         } 
         print("Innerloop:${j}"); 
      } 
   } 
}

Outerloop: 0 
Innerloop: 0 
Innerloop: 1 
Innerloop: 2 

Outerloop: 1 
Innerloop: 0 
Innerloop: 1 
Innerloop: 2 

Outerloop: 2 
Innerloop: 0 
Innerloop: 1 
Innerloop: 2