Storage vs. memory in Solidity
Chinweuba Elijah AzubuikeOverview
memory is a keyword used to store data for the execution of a contract. It holds functions argument data and is wiped after execution.
storage can be seen as the default solidity data storage. It holds data persistently and consumes more gas.
storage | memory |
Stores data in between function calls | Stores data temporarily |
The data previously placed on the storage area is accessible to each execution of the smart contract | Memory is wiped completely once code is executed |
Consumes more gas | Has less gas consumption, and better for intermediate calculations |
Holds array, state and local variables of struct | Holds Functions argument |
Example of storage
pragma solidity ^0.5.12;
// Creating a contract
contract fellowCoders
{
// Initialising array coders
int[] public coders;
// Function to insert values
// in the array coders
function Numbers() public
{
coders.push(1);
coders.push(2);
//Creating a new instance
int[] storage myArray = coders;
// Adding value to the
// first index of the new Instance
myArray[0] = 0;
}
}Explanation
-
Line 4: We create a contract,
fellowcoders, to illustrate thestoragekeyword. -
Line 7: We Initialize an array,
coders. -
Line 11: We create a
Numbersfunction to insert values in the array coders. -
Line 17: We create a new instance
myArray. -
Line 21: We add a value to the first index of the new instance.
Example of memory
pragma solidity ^0.5.12;
// Creating a contract
contract fellowCoders
{
// Initialising array coders
int[] public coders;
// Function to insert
// values in the array
// coders
function Numbers() public
{
coders.push(1);
coders.push(2);
//creating a new instance
int[] memory myArray = coders;
// Adding value to the first
// index of the array myArray
myArray[0] = 0;
}
}Explanation
-
Line 4: We create a contract,
fellowCoders, to illustrate thememorykeyword. -
Line 7: We initialize a
codersarray. -
Line 12: We create a function to insert values in the
codersarray. -
Line 18: We use the
memorykeyword to create a new instance. -
Line 22: We add value to the first index of the array.
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Chinweuba Elijah AzubuikeView all Courses
