Solidity is a statically typed programming language, Each variable you use in solidity must declare of type. Like any programming language, It is used to store the value in a variable.
Variables in solidity are used to store the data in the blockchain as well as used in functions for processing.
This tutorial covers
- Declare variable Syntax
- Solidity variable examples
Solidity Variable Syntax
variables are declared with the type of variable and visibility or access modifier and variable name.
datatype access-modifier variablename
Datatype is an inbuilt or custom user-defined data type such as boolean, or unit256.
access-modifier: Also called visibility and how and where the variable values are accessible.
Possible values are
- public
- private
- internal
- external
variablename is a valid identifier in solid, It contains a combination of alphabets and numeric. The reserved keywords are not used.
The variables can be declared in Contracts or functions
Variable type initial default values
creating a variable does assign default initial values.
Based on data type, initial values are different as given.
These default values are assigned when variables are not assigned any value.
| Data Type | Default value | Value/Reference type |
|---|---|---|
| bool | false | Value type |
| string | empty string("") | Value type |
| int/uint | 0 | Value type |
| fixed/ufixed types | 0.0 | Value type |
| address | 0x0000000000000000000000000000000000000000 | Value type |
| enum | first element of an enum constant | Value type |
| Internal function | It returns an empty function, if it contains retur, It returns empty values | Value type |
| external function | function returns | Value type |
| mapping | blank empty mapping | Reference type |
| struct | returns a struct with initial default values | Reference type |
| Fixed array | All the items are default values | Reference Type |
| Dynamic array | Empty Array([]) | Reference Type |