Question

我有这样的数据；

@GeneratedValue(strategy = GenerationType.IDENTITY)

我正在使用该代码读取文件；

let sandbox;
let createQueryBuilderStub;
let mock;
let fakeQueryBuilder = new SelectQueryBuilder<Pratica>(null);

beforeEach(() => {
    sandbox = sinon.createSandbox();

    mock = sandbox.mock(fakeQueryBuilder);

    createQueryBuilderStub = sandbox.stub(Repository.prototype, 
'createQueryBuilder').withArgs("p").returns(fakeQueryBuilder);
});

afterEach(() => {
    sandbox.restore();
});

describe('PraticaRepository#list', () => {

    it('should get the result with no filters', async () => {

        mock.expects('leftJoinAndSelect').twice().returns(fakeQueryBuilder);
        mock.expects('where').never();
        mock.expects('andWhere').never();
        mock.expects('getSql').once();
        mock.expects('getMany').once();

        let cut = new PraticaRepository();

        const appo = cut.list();

        sinon.assert.calledOnce(createQueryBuilderStub);
        mock.verify();

    });
})

我的问题是，如何将这些数据存储在链接列表中？我创建一个节点来存储StockCode，描述和数量。我如何从缓冲区获取该列数据？

我只能使用 iostream，ctime，fstream，string 库来解决该问题。没有向量。

Answer 1

首先，老师强迫人们使用C ++中的原始指针和C-Style数组是一种可耻的事情。并且，为std::list重新发明轮子。

我什至不能在给定包含列表下使用std::unique_ptr。所以，主请原谅我以下几点：

#include <iostream>
#include <fstream>
#include <string>

constexpr size_t NumberOfInvoiceDataEntries = 8;

// Make reading easier
// Lord forgive me for using plain C-Style arrays
using InvoiceDataEntry = std::string[NumberOfInvoiceDataEntries];

// Split line into columns
void splitLine(const std::string& csvLine, InvoiceDataEntry csvColumns) {

    // Initialize all needed value
    size_t columnIndex{ 0U }; size_t startPos{ 0U }; size_t i = 0U;

    // Iterate over all characters in the string
    do {
        // If we found semicolon or end of string, then we copy the sub-string
        if (csvLine[i] == ';' || i == csvLine.size()) {

            // Copy to column array.
            csvColumns[columnIndex++] = csvLine.substr(startPos, i - startPos);;
            startPos = i + 1;
        }
        ++i;
    } while (i <= csvLine.size());
}

struct InvoiceData {
    // Our data
    InvoiceDataEntry data{};

    // Overwrite inserter operator for easier input
    friend std::istream& operator >> (std::istream& is, InvoiceData& id) {
        if (std::string line{}; std::getline(is, line) && !line.empty()) {
            splitLine(line, id.data);
        }
        return is;
    }

    // Overwrite extractor operator for easier output
    friend std::ostream& operator << (std::ostream& os, const InvoiceData& id) {
        return os << "\nInvoice No:   " << id.data[0] << "\nStock Code:   " << id.data[1] << "\nDescription:  " << id.data[2]
            << "\nQuantity:     " << id.data[3] << "\nInvoice Date: " << id.data[4] << "\nUnit Price:   " << id.data[5]
            << "\nCustomer ID:  " << id.data[6] << "\nCountry:      " << id.data[7] << "\n";
    }
};

struct LinkedListInvoiceData {

    // Destructor: clean up newed memory
    ~LinkedListInvoiceData() { delete next; }

    void add(const InvoiceData& id) {

        // Search end of linked list
        LinkedListInvoiceData* current = this;
        while (current->next != nullptr)
            current = current->next;

        // Assign new invoice data.
        current->invoiceData = id;
        current->next = new LinkedListInvoiceData();
    }

    void print() {

        LinkedListInvoiceData* current = this;
        while (current != nullptr) {
            std::cout << current->invoiceData;
            current = current->next;
        }
        return;
    }

private:
    LinkedListInvoiceData* next{ nullptr };
    InvoiceData invoiceData{};
};

const std::string fileName("r:\\myData.csv");

int main() {  

    // Open file and check if it is open
    if (std::ifstream ifs(fileName); ifs) {

        // The linked list with the invoice data
        LinkedListInvoiceData llid{};

        // Read all lines of file
        for (InvoiceData id; ifs >> id; ) 
            llid.add(id);
        // Print complete linked list
        llid.print();
    }
    return 0;
}

请注意。我的链表不是通用的，并且末尾有一个空元素。您可以实现自己的链接列表，也可以从网上下载数千个示例之一。

读取和存储CSV数据

1 个答案: