[英]Read columns from a comma delimited data file c++
我一直在尝试阅读以下数据表并为 HUB(行)创建一个对象,为大陆(列)创建另一个对象。 由于我不是 C++ 经验丰富的用户,因此我一直面临一些困难。 数据如下。 HUB 和破折号后面的数字表示从集线器开始的顺序。 每个大洲下的其他数字是 HUB 和大洲之间的相应成本和资费。 我希望能够 cout 例如跟随并得到 73 的结果。 cout << hub(1)->cont(USA)->transport() << endl;
,USA,EUROPE,ASIA
HUB1-12000,,,
Transportation Cost,73,129,141
Tariffs,5,5,1
ShippingType,a,b,c
OtherFees,0.6,0.3,0.8
HUB2-11000,,,
Transportation Cost,57,101,57
Tariffs,7,7,5
ShippingType,b,b,d
OtherFees,0.7,0.3,0.6
真的很感谢你的帮助。 这是我迄今为止尝试过的:
void Hub()
{
string file = "/hubs.csv";
// 1-First read the first line and save the continent name
string str, field;
getline( fin, str );
vector<string> contList;
stringstream linestr( str );
while ( linestr.good() )
{
getline( linestr, field, ',' );
string contname;
contList.push_back(contname);
}
// 2-Then read the rest
getline( fin, str );
while ( !fin.eof() ) // Read the whole file
{
stringstream linestr( str );
string contname, order;
if ( qstr[0] == 'HUB1' || qstr[0] == 'HUB2')
{
// Read the name of the hub
getline( linestr, hubname, ',' ); // Read the hub name
getline( linestr, order, ',' ); // Read the order quantityity
int quantity;
istringstream orderstream( order);
orderstream >> quantity;
// Find the hub and add the order to the hub
Hub* hub = glob->FindHubName( hubname ); // this returns a pointer
if ( glob->FindHubName( hubname ) == nullptr )
{
hubNotFound.push_back( hubname );
getline( fin, qstr );
continue;
}
hub->TotalOrder( quantity );
}
else if ( qstr[0] != 'HUB1' || qstr[0] != 'HUB2')
{
// Read costs and tariffs
cout << hub(1)->cont(ASIA)->transport()
}
getline( fin, qstr );
}
fin.close();
}
像这样的东西:
#include <iostream>
#include <fstream>
#include <boost/tokenizer.hpp>
#include <string>
int main() {
using namespace std;
using namespace boost;
string line, file_contents;
fstream file("test.csv");
if (!file.is_open()) {
cerr << "Unable to open file" << endl;
return 1;
}
getline(file, line);
tokenizer<> tok_head(line);
int n_columns = 0;
for (tokenizer<>::iterator beg=tok_head.begin(); beg!=tok_head.end(); ++beg) {
cout << *beg << '\t';
n_columns++;
}
cout << endl;
while (getline(file, line)) {
file_contents += line;
}
file.close();
tokenizer<> tok(file_contents);
int i = 0;
for (tokenizer<>::iterator beg=tok.begin(); beg!=tok.end(); ++beg, ++i) {
cout << *beg;
if (i % n_columns) {
cout << '\t';
} else {
cout << endl;
}
}
return 0;
}
生成文件
all: t
t: csv.cpp
g++ -I /usr/include/boost csv.cpp -o t
看起来您必须使用不同的逻辑解析每一行,因此您应该首先检查第一列并使用它应用适当的逻辑,下面是一些伪代码:
std::fstream fs("test.txt");
std::string line;
//
// Read line by line
while (std::getline(fs, line)) {
std::istringstream str(line);
std::string rec_type;
// Read record type (your first two lines looks like are of no type?)
if ( !std::getline(str, rec_type, ',') )
continue;
// Decide type of record, and parse it accordingly
if ( rec_type == "Transportation Cost") {
std::string val;
// Read comma delimited values
if ( !std::getline(str, val, ',') )
continue;
int ival1 = std::stoi(val);
if ( !std::getline(str, val, ',') )
continue;
int ival2 = std::stoi(val);
// ...
}
if ( rec_type == "Tariffs") {
std::string val;
if ( !std::getline(str, val, ',') )
continue;
int ival = std::stoi(val);
// ...
}
}
一种方法是将每一行视为单独的记录和对象。
让对象读取它们的数据。
例如:
class Tariff
{
int values[3];
public:
friend std::istream& operator>>(std::istream& input, Tariff& t);
};
std::istream& operator>>(std::istream& input, Tariff& t)
{
// Read and ignore the label "Tariff"
std::string name;
std::getline(input, name, ','); // Read until ',' delimiter.
input >> t.value[0];
// Note: the ',' is not a digit, so it causes an error state,
// which must be cleared.
input.clear();
input >> t.value[1];
input.clear();
input >> t.value[2];
input.clear();
}
另一种方法是先读取标签,然后委托给读取行的函数。
std::string row_text;
std::getline(text_file, row_text); // Read in first line and ignore.
while (std::getline(text_file, row_text))
{
std::istringstream text_stream(row_text);
std::string label;
std::getline(text_stream, label, ','); // Parse the label.
// Delegate based on label.
// Note: can't use switch for strings.
if (label == "Tariffs")
{
Input_Tariff_Data(text_stream);
}
else if (label == "ShippingType")
{
Input_Shipping_Type_Data(text_stream);
}
//...
} // End-while
if-else
梯形图可以由使用函数指针的查找表代替。 有时表格更容易阅读。
typedef void (*P_Input_Processor)(std::istringstream& text_stream);
struct Table_Entry
{
char const * label;
*P_Input_Processor input_processor;
};
//...
const Table_Entry delegation_table[] =
{
{"Tariffs", Input_Tariff_Data},
{"ShippingType", Input_Shipping_Type_Data},
};
const unsigned int entry_quantity =
sizeof(delegation_table) / sizeof(delegation_table[0]);
// ...
std::string row_text;
std::getline(input_file, row_text); // Read and ignore first line.
while (std::getline(input_file, row_text))
{
// Create a stream for parsing.
std::istringstream text_stream(row_text);
// Extract label text
std::string label;
std::getline(text_stream, label, ',');
// Lookup label in table and execute associated function.
for (unsigned int index = 0; index < entry_quantity; ++index)
{
if (label == delegation_table[index].name)
{
// Execute the associated input function
// by derferencing the function pointer.
delegation_table[index](text_stream);
break;
}
}
}
查找表的替代方法是使用:
std::map<std::string, P_Input_Processor>
或者std::map<std::string, void (*P_Input_Processor)(std::istringstream&)>
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