我正在努力学习如何使用课程，我想我会创建一些超市系统来帮助我学习。将文本文件中的所有值保存到临时变量后，如何使用它们创建对象？我假设我想要“购买”每个项目一个对象？
如果您有关于如何改进我的代码的任何其他提示，请在几天前我刚开始使用C ++时提及它们。
我的文字文件如下：
42 68 Apples
35 1 Oranges
70 25 Bananas
我的代码如下：
// Classes.cpp : Defines the entry point for the console application.
//
#include "stdafx.h"
#include <iostream>
#include <string>
#include <fstream>
#include <sstream>
#include <vector>
class Products {
private:
int price;
int ID;
int quantity;
public:
void setPrice(int newPrice) {
price = newPrice;
}
void setID(int newID) {
ID = newID;
}
void setQuantity(int newQuantity) {
quantity = newQuantity;
}
int getPrice() {
return price;
}
int getID() {
return ID;
}
int getQuantity() {
return quantity;
}
};
int main()
{
std::string line;
std::string input;
std::string temp;
std::string temp2;
std::string temp3;
int counter = 0;
while (input != "e" && input != "r") {
std::cout << "Do you want to (r)ead the inventory or (e)dit it? (input 'r' or 'e'): ";
getline(std::cin, input);
}
if (input == "r") {
std::ifstream pFile ("products.txt");
if (pFile.is_open()) {
while (getline(pFile, line)) {
std::istringstream iss(line);
iss >> temp >> temp2 >> temp3;
counter++;
}
}
}
return 0;
}
答案 0 :(得分：0)
查看您正在使用的文本文件，并尝试使用以下信息填充一组类：
文字档案
42 68 Apples 35 1 Oranges 70 25 Bananas
查看文本文件后，您有int后跟space，然后是另一个int，后跟另一个space，最后是varying size of char[]。我们可以使用此信息来创建您的class或struct，这就是我根据正在读取或解析的文件中的内容创建class的方法。
<强> Produce.h
#ifndef PRODUCE_H
#define PRODUCE_H
#include <string>
class Produce {
private:
unsigned price_; // Normally would use float but will use unsigned for simplicity
unsigned quantity_;
std::string name_; // You could use the int as an id as you were using
public:
Produce() {} // Default Constructor
~Produce() {} // Default Destructor
// User Constructor
Produce(const std::string& name, const unsigned& price, const unsigned& qty )
: name_(name), price_(price), quantity_( qty ) {}
// Copy By Const Reference Constructor
Produce(const Produce& other) {
name_ = other.name_;
price_ = other.price_;
quantity_ = other.quantity_;
}
// Assignment Operator
Produce& operator=(const Produce& other) {
name_ = other.name_;
price_ = other.price_;
quantity_ = other.quantity_;
return *this;
}
// Setters & Getters
void setOrChangePrice(const unsigned& priceChange) {
price_ = priceChange;
}
unsigned getPrice() const { return price_; }
void setName(const std::string& name) {
// Already Has A Name? Return!
if (!name_.empty())
return;
}
std::string getName() const { return name_; }
void setOrChangeQuantity(const unsigned& qty) {
quantity_ = qty;
}
unsigned getQuantity() const {
return quantity_;
}
};
#endif // PRODUCE_H
<强> Produce.cpp
#include "Produce.h"
// Normally Constructor(s) & Function Definitions Would Go Here
// Since this is a simple class; I declared & defined them in the header.
<强> Inventory.h
#ifndef INVENTORY_H
#define INVENTORY_H
#include <vector>
#include "Produce.h"
class Inventory {
private:
std::vector<Produce> produce_;
public:
Inventory() {}
~Inventory() {
if (!produce_.empty()) {
produce_.clear();
}
}
std::vector<Produce> getProduceList() const {
return produce_;
}
unsigned getProduceListSize() const {
return static_cast<unsigned>( produce_.size() );
}
void addProduce(const Produce& produce) {
produce_.push_back(produce);
}
Produce getProduce(const std::string& name) const {
for (unsigned n = 0; n < produce_.size(); ++n) {
if (name == produce_[n].getName()) {
return produce_[n];
} else {
return Produce();
}
}
}
unsigned getPrice(const std::string& name) const {
for (unsigned n = 0; n < produce_.size(); ++n) {
if (name == produce_[n].getName()) {
return produce_[n].getPrice();
} else {
return 0;
}
}
}
unsigned getQuantity( const std::string& name ) const {
for (unsigned n = 0; n < produce_.size(); ++n) {
if (name == produce_[n].getName()) {
return produce_[n].getQuantity();
} else {
return 0;
}
}
}
};
#endif // INVENTORY_H
<强> Inventory.cpp
#include "Inventory.h"
<强> Main.cpp的
// #include <vector> // Also Included In Inventory.h
// #include <string> // Also Included In Produce.h
#include <iostream>
#include <fstream>
// #include "Produce.h" // Also Included In Inventory.h
#include "Inventory.h"
int main( ) {
// Same As Your Text File
std::string strFilename("ProduceInventory.txt");
std::ifstream fileIn;
// Temps
unsigned price = 0;
unsigned qty = 0;
std::string name;
Inventory inventory;
fileIn.open(strFilename.c_str());
if (!fileIn.is_open()) {
std::cout << "Can not read file\n";
}
while (fileIn >> price >> qty >> name) {
Produce produce(name, price, qty);
inventory.addProduce(produce);
}
if ( fileIn.is_open() ) {
fileIn.close();
}
// Test Our Inventory From File
for (unsigned n = 0; n < inventory.getProduceListSize(); n++) {
std::cout << "Name: " << inventory.getProduceList()[n].getName() << " "
<< "Price: " << inventory.getProduceList()[n].getPrice() << " "
<< "Qty: " << inventory.getProduceList()[n].getQuantity() << "\n";
}
std::cout << std::endl;
// Check To See If Our Search Method Works
std::cout << "Enter a product type by name to get its price and qty on hand.\n";
name.clear(); // reuse
std::cin >> name;
Produce p = inventory.getProduce(name);
if (p.getName().empty()) {
std::cout << "We either do not carry this produce or we are out of stock\n";
} else {
std::cout << "Our price is " << p.getPrice() << " and we have " << p.getQuantity() << " on hand\n";
// Or
std::cout << "Our price is " << inventory.getPrice(name) << " and we have " << inventory.getQuantity(name) << " on hand\n";
}
return 0;
}
现在这只是可以做到的很多方法之一;还要确保您的文本文件位于IDE工作目录的适当位置，或者您指定了正确的路径以及文件名和扩展名，以便能够首先打开和读取该文件。
这些代码中的大部分都可能被罚款更多;但我正在展示如何使用std::vector<T>容器及其一些功能，以及如何迭代它们并检索其数据。当您知道文本文件的确切格式时，这是解析简单文本文件的基本方法，并且对于每一行，您将以相同的顺序具有相同的数据类型。
这不适用于每种文件解析，因为它取决于文件的格式。例如，另一个文件可能具有从一行到下一行的不同类型的数据，并且可能具有关键字或标签以描述接下来将要出现的数据类型。对于那种解析，您必须首先将整行读入字符串流，然后您必须能够通过令牌解析该字符串流以提取数据。有时解析文件可能有多行属于一个数据集，因此您必须通过块或blob进行解析。
解析文本文件比二进制文件格式更难解析，因为你必须检查文本的每一行和字符，你还必须谨慎 字符返回，新行字符等。使用二进制格式，您只需要知道要读入多少字节以及预期的数据类型。关于如何从文件中解析数据，仅就此主题编写了许多书籍。没有一种适合所有人的简单方法。