Data types
Variables
Constants
Immutables
Data types
Mainly we have 4 types of data types in solidity language.
- boolean
- uint
- int
- address
boolean:
As we know we can specify a variable is true or false.
uint:
Its stands for unsigned integers. we can specify only a non negative integers.
uint can have a range of sizes like uint8, uint16 ... uint256
uint8 = 0 to 2**8-1. same goes with others.
int:
As we know we can specify an integer and negative numbers are allowed for int type. like uint here also we can specify a range of different sizes.
address:
address holds a 20 byte value which is the size of a ethereum address. additionally we can specify as address payable
which can transfer or send fund to the address.
// SPDX-License-Identifier: MIT
pragma solidity ^0.8.9;
contract ExampleDataType {
bool public boo = true;
uint public age = 27;
int public num = -3;
address public addr = 0x8CA434018A6d.....;
}
Variables
Variables are containers where we store some data. we have three type of variables.
- state
- local
- global
state:
State variables are declared inside a function and not stored in the blockchain.
local:
Local variables are declared outside of the function and stored in the blockchain.
global:
Global variables provides information about the blockchain.
// SPDX-License-Identifier: MIT
pragma solidity ^0.8.9;
contract ExampleVariable {
string public name = "jon doe"; // state variable.
function changeName() public {
uint pin = 500082; // local variable
address sender = msg.sender; // global variable
}
}
constants
constants are variables that can not be modified. Their value is hard coded and using constants we can save gas.
// SPDX-License-Identifier: MIT
pragma solidity ^0.8.9;
contract ExampleConstants {
address public constant ADDR = 0xee3445e...;
uint256 public constant MAX_NFT = 1000
}
Immutable
immutable variables are like constants. Value of immutable variables can be set inside the constructor but can not be modified afterwords.
// SPDX-License-Identifier: MIT
pragma solidity ^0.8.9;
contract ExampleConstants {
address public immutable MY_ADDRESS;
constructor() {
MY_ADDRESS = msg.sender;
}
}
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