Dart Programming - Boolean

void main() { 
   bool test; 
   test = 12 > 5; 
   print(test); 
}

It will produce the following output −

true 

Example

Unpke JavaScript, the Boolean data type recognizes only the pteral true as true. Any other value is considered as false. Consider the following example −

var str =  abc ; 
if(str) { 
   print( String is not empty ); 
} else { 
   print( Empty String ); 
} 

The above snippet, if run in JavaScript, will print the message ‘String is not empty’ as the if construct will return true if the string is not empty.

However, in Dart, str is converted to false as str != true. Hence the snippet will print the message ‘Empty String’ (when run in unchecked mode).

Example

The above snippet if run in checked mode will throw an exception. The same is illustrated below −

void main() { 
   var str =  abc ; 
   if(str) { 
      print( String is not empty ); 
   } else { 
      print( Empty String ); 
   } 
}

Unhandled exception: 
type  String  is not a subtype of type  bool  of  boolean expression  where 
   String is from dart:core 
   bool is from dart:core  
#0 main (file:///D:/Demos/Boolean.dart:5:6) 
#1 _startIsolate.<anonymous closure> (dart:isolate-patch/isolate_patch.dart:261) 
#2 _RawReceivePortImpl._handleMessage (dart:isolate-patch/isolate_patch.dart:148)

Empty String