Bool is a boolean data type in Dart language.

It uses to store two values true or false values. These are also called compile-time boolean constants.

true and false values are reserved words, that are not used as an identifier for variables or function or class names in Dart language.

Bool type is used in the following cases.

  • Variable can be declared with this types to store true or false conditional expressions.
  • Dart expressions are evaluated as true or false in conditional expressions such as if statements.
  • Also used dart operator produces bool values

How to Declare bool variable?

Variables are declared like a normal variable in dart. The default value for the boolean type is null. Boolean values are declared and assigned with values on the same line.

bool variable_name=true;
bool variable_name1=false;

variable_name is a valid identifier in the dart programming language.

true and false values are only values that are assigned to the bool type.

If you assign with any other values, It throws Error: Undefined name.

Following are invalid bool types

  bool flag='True';
  bool flag='true';

Error: A value of type ‘int’ can’t be assigned to a variable of type ‘bool’.

  bool flag=1;

How do you write a Boolean in darts?

Boolean is a predefined inbuilt one of data type in a dart programming language. It stores true and false values only.

Here is an example

void main() {
  bool? flag;
  print(flag);
}

Bool value can be used in a conditional expression.

Here is an if conditional expression example

void main() {
  var flag = true;
  if (flag) {
    print("Condition satisfied.");
  } else {
    print("Condition not satisfied.");
  }
}

Similarly, You can combine boolean variables with logical boolean (&&,||,!)operators.

void main() {
  var flag = true;

  print(true || false); // true
  print(true && false); //false
  print(true && true); //true
}