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 blockchain as well as used in functions for processing.
This tutorials 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, 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 with default initial values.
Based on data type, initial values are different as given.
These default values are assigned when variables are not assigned with 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 empty function, if it conatains retur, It return empty values | Value type |
external function | function returns | Value type |
mapping | blank empty mapping | Reference type |
struct | returns an struct with initial default values | Reference type |
Fixed array | All the items are default values | Reference Type |
Dynamic array | Empty Array([] ) |
Reference Type |