Array can have a compile-time fixed size or a dynamic size.
// SPDX-License-Identifier: MIT
pragma solidity ^0.7.6;
contract Array {
// Several ways to initialize an array
uint[] public arr;
uint[] public arr2 = [1,2,3];
// Fixed sized array, all elements initialize to 0
uint[10] public myFixedSizeArr;
function get(uint i) public view returns (uint) {
return arr[i];
}
// Solidity can return the entire array.
// But this function should be avoided for
// arrays that can grow indefinitely in length.
function getArr() public view returns (uint[] memory) {
return arr;
}
function push(uint i) public {
// Append to array
// This will increase the array length by 1.
arr.push(i);
}
function pop() public {
// Remove last element from array
// This will decrease the array length by 1
arr.pop();
}
function getLength() public view returns (uint) {
return arr.length;
}
function remove(uint index) public {
// Delete does not change the array length.
// It resets the value at index to it's default value,
// in this case 0
delete arr[index];
}
}
contract CompactArray {
uint[] public arr;
// Deleting an element creates a gap in the array.
// One trick to keep the array compact is to
// move the last element into the place to delete.
function remove(uint index) public {
// Move the last element into the place to delete
arr[index] = arr[arr.length - 1];
// Remove the last element
arr.pop();
}
function test() public {
arr.push(1);
arr.push(2);
arr.push(3);
arr.push(4);
// [1, 2, 3, 4]
remove(1);
// [1, 4, 3]
remove(2);
// [1, 4]
}
}
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