不可变长度数组

声明

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pragma solidity ^0.8.0;

contract FixArrayDemo{
    uint [3] _nums = [1,2,3];
}

获取数组长度和遍历数组

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pragma solidity ^0.8.0;

contract FixArrayDemo{
    uint [3] _nums = [1,2,3];

    function AddOP() view public returns (uint) {
        uint result = 0;
        for (uint i=0;i<_nums.length;i++){
            result += _nums[i];
        }
        return result;
    }
}

修改数组中的元素值

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pragma solidity ^0.8.0;

contract ArrayDemo{
    uint [3] _nums = [1,2,3];


    function AddOP() view public returns (uint) {
        uint result = 0;
        for (uint i=0;i<_nums.length;i++){
            result += _nums[i];
        }
        return result;
    }
    
}

注:不能向固定数组中添加新元素。

可变长度数组

同样可以声明，获取长度，循环遍历，修改数组中的元素值，与不可变长度数组不同的是[]里面没有数字。

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pragma solidity ^0.8.0;

contract ArrayDemo{
    uint [] _nums = [1,2,3];


    function AddOP() view public returns (uint) {
        uint result = 0;
        for (uint i=0;i<_nums.length;i++){
            result += _nums[i];
        }
        return result;
    }
}

修改数组的长度

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pragma solidity ^0.8.0;

contract ArrayDemo{
    uint [] _nums = [1,2,3];
    
    //...

    function addItem(uint v) public {
        _nums.push(v);
    }

    function popItem() view public returns(uint){
       return _nums.pop();
    }
    
    function visitItem(uint idx) view public returns(uint){
        require(idx<=_nums.length-1,"out of index.");
        return _nums[idx];
    }
    
    function deleteItem(uint idx) public{
        delete(_nums[idx]);
    }

    // 删除数组元素，并且长度减1
    function removeAt(uint idx) public {
        require(idx>=0 && idx<arr.length);
        delete(_nums[idx]);
        arr.pop();
    }

    function showArr() view public returns(uint[] memory){
        return _nums;
    }

}