Dart Variables

In this chapter, we will learn about Dart variables and constants in dart, how to declare and initialize them.

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Dart Variables

Variable is an identifier that stores data. For example,

var name = “Jackson”;

Here name is a variable that stores the string data Jackson.

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Declaring Variables

To declare variables, keyword var is used. For example,

var number;

Dart also supports type-checking which helps in declaring the variables. For example,

int number; // for integer values

String name; // for string values

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Initialising Variables

To assign a value to variables, the assignment operator (=) is used. For example,

var number = 5;

Here number is a variable and value 5 is assigned to the number variable.

Similarly we can pass specific values to the variables. For example,

String name = “Lauren”;

If we try to pass integer values to string variable, then we get the error.

String name = 4; // Error: A value of type 'int' can't be assigned to a variable of type 'String'.

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Changing values of variables

The variables mean that the values can be changed. We can simply change the value of a variable by assigning a new value to the variable.

For example,

var name = ‘Sam’;

name = ‘John’;

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Rules for naming a Dart variable

1. Variable names can consist of numbers and alphabets, underscore (_) and the dollar ($) sign. For example,

var name = ‘Sam’;

var $name = ‘Pam’;

int number = 4.4;

2. Variable names cannot contain keywords. For example,

var void = ‘Sam’;

3. Variable names should be alphabet and cannot start with numbers. For example,

var 2name = ‘Sam’;

4. Dart is case-sensitive. Hence a and A are different. For example,

var a = ‘Sam’;

var A = ‘Smith’;

A is not equal to a.

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Dart Constants

Dart constants are similar to the dart variables. They are used to store values. The only difference is that the values of a constant cannot be changed afterwards.

The constants are denoted by the keyword final and const. For example,

final name = ‘Sam’;

const number = 500;

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We will learn about Dart Operators in the next chapter.