What are variables in Dart ? link

In Dart, variables are used to store data values. Each variable has a specific data type, which determines the kind of values it can hold.

Dart is a statically typed language, which means that variables must be declared with their data types before they can be used.

You are familiar with the topic ? Check your knowlege

Variable Declaration link

Rules for declaring variable in dart

There are certain guidelines we need to follow while declaring the varibales. They are:

• A variable name must start with a letter or the underscore character _.
• A variable name cannot start with a digit.
• A variable name can only contain alphanumeric characters and underscores (A-z, 0-9, and _ ).
• Variable names are case-sensitive (age, Age and AGE are three different variables).

In Dart, variables can be declared using the var keyword followed by the variable name and an optional initial value. Here’s an example:

Example

  var name = 'John';
  

In the above example, the variable name is declared using the var keyword. The variable name is name and the initial value is 'John'. The variable name is of type String because the initial value is a string.

The var keyword is optional. You can also declare variables using the data type of the initial value. Here’s an example:

  String name = 'John';
  

In the above example, the variable name is declared using the String data type. The variable name is name and the initial value is 'John'. The variable name is of type String because the initial value is a string.

Note:

Variable Assignment link

In Dart, variables can be assigned new values using the assignment operator =. Here’s an example:

Example

  var name = 'John';
name = 'Jane';
  

Output

  Jane
  

code Try Yourself

In the above example, the variable name is assigned the value 'John' and then the value 'Jane'.

Types of varibales link

In dart, there are two types of varibales :

Public Variables

   int name = "Flutter World"; 
  

Private variables

   int _name = "Flutter World"; 
  

Datatypes in Dart link

In Dart, variables can be declared using the following data types:

• int - for integer values
• double - for floating-point values
• num - for numeric values
• String - for string values
• bool - for boolean values
• List - for list values
• Map - for map values
• Set - for sets
• dynamic - for dynamic values

We will discuss more about List, Map and Set in the Dart collections chapter.

int datatype in dart link

In Dart, the int data type is used to represent integer values. Here’s an example:

Example

  int age = 20;
  

In the above example, the variable age is declared using the int data type.

The variable name is age and the initial value is 20. The variable age is of type int because the initial value is an integer.

double datatype in dart link

In Dart, the double data type is used to represent floating-point values. Here’s an example:

Example

  double pi = 3.14;
  

In the above example, the variable pi is declared using the double data type.

The variable name is pi and the initial value is 3.14. The variable pi is of type double because the initial value is a floating-point(decimal) value.

num datatype in dart link

In Dart, the num data type is used to represent numeric values. Here’s an example:

Example

  num pi = 3.14;
  

In the above example, the variable pi is declared using the num data type. The variable name is pi and the initial value is 3.14. The variable pi is of type num because the initial value is a numeric value.

num can store both int and double values.

String Datatype in Dart link

In Dart, the String data type is used to represent string values. Here’s an example:

Example

  String name = 'John';
  

In the above example, the variable name is declared using the String data type. The variable name is name and the initial value is 'John'. The variable name is of type String because the initial value is a string value.

String Manipulation link

Manipulation of string means to change the string in some way. Dart supports the following string manipulation methods:

• Concatenation
• Interpolation

String Concatenation in Dart link

Concatenation is the process of joining two or more strings together. Dart supports the + operator for concatenation.

Syntax

  
string1 + string2
  

Example

  
void main() {
   String str1 = "Hello";
   String str2 = "World";
   print(str1 + str2);
}
  

Output

  HelloWorld
  

code Try Yourself

String Interpolation in Dart link

Interpolation is the process of inserting the value of an expression or variable into a string. Dart supports the $ operator for interpolation.

Syntax

  
string1 $expression string2
  

Example

  
void main() {
   String str1 = "Hello";
   String str2 = "World";
   print("$str1 $str2");
}
  

Output

  Hello World
  

code Try Yourself

bool datatype in dart link

In Dart, the bool data type is used to represent boolean values. Here’s an example:

Example

  bool isMarried = false;
  

In the above example, the variable isMarried is declared using the bool data type. The variable name is isMarried and the initial value is false. The variable isMarried is of type bool because the initial value is a boolean value.

Note:

dynamic datatype in dart link

In Dart, the dynamic data type is used to represent dynamic values. Here’s an example:

Example

  dynamic age = 20;
  

In the above example, the variable age is declared using the dynamic data type. The variable name is age and the initial value is 20.

The variable age is of type dynamic because the initial value is a dynamic value.

Type Inference link

In Dart, the var keyword can be used to declare variables without specifying their data types. Here’s an example:

Example

  var name = 'John';
  

In the above example, the variable name is declared using the var keyword. The variable name is name and the initial value is 'John'. The variable name is of type String because the initial value is a string.

In Dart, the var keyword can also be used to declare variables without specifying their data types. Here’s an example:

  var age = 20;
  

In the above example, the variable age is declared using the var keyword. The variable name is age and the initial value is 20. The variable age is of type int because the initial value is an integer.

Quiz link

Check your knowlege with the quiz below.