Blockchain Developer's Guide

Using var

Solidity provides the var keyword to declare variables. The type of the variable in this case is decided dynamically depending on the first value assigned to it. Once a value is assigned, the type is fixed, so if you assign another type to it, it will cause type conversion.

Here is an example to demonstrate var:

int256 x = 12; //y type is int256 var y = x; uint256 z= 9; //exception because implicit conversion not possible y = z; 

Remember that var cannot be used when defining arrays and maps. And it cannot be used to define function parameters and state variables.