solidity 语法--array
数组可以具有编译时固定大小或动态大小。
// SPDX-License-Identifier: MIT
pragma solidity ^0.8.13;
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];
}
function examples() external {
// create array in memory, only fixed size can be created
uint[] memory a = new uint[](5);
}
}
array这段不能进行编译,看看吧
array移除元素,通过从右向左移动元素来删除数组元素
// SPDX-License-Identifier: MIT
pragma solidity ^0.8.13;
contract ArrayRemoveByShifting {
// [1, 2, 3] -- remove(1) --> [1, 3, 3] --> [1, 3]
// [1, 2, 3, 4, 5, 6] -- remove(2) --> [1, 2, 4, 5, 6, 6] --> [1, 2, 4, 5, 6]
// [1, 2, 3, 4, 5, 6] -- remove(0) --> [2, 3, 4, 5, 6, 6] --> [2, 3, 4, 5, 6]
// [1] -- remove(0) --> [1] --> []
uint[] public arr;
function remove(uint _index) public {
require(_index < arr.length, "index out of bound");
for (uint i = _index; i < arr.length - 1; i++) {
arr[i] = arr[i + 1];
}
arr.pop();
}
function test() external {
arr = [1, 2, 3, 4, 5];
remove(2);
// [1, 2, 4, 5]
assert(arr[0] == 1);
assert(arr[1] == 2);
assert(arr[2] == 4);
assert(arr[3] == 5);
assert(arr.length == 4);
arr = [1];
remove(0);
// []
assert(arr.length == 0);
}
}
通过将最后一个元素复制到要删除的位置来删除数组元素
// SPDX-License-Identifier: MIT
pragma solidity ^0.8.13;
contract ArrayReplaceFromEnd {
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 = [1, 2, 3, 4];
remove(1);
// [1, 4, 3]
assert(arr.length == 3);
assert(arr[0] == 1);
assert(arr[1] == 4);
assert(arr[2] == 3);
remove(2);
// [1, 4]
assert(arr.length == 2);
assert(arr[0] == 1);
assert(arr[1] == 4);
}
}