格式化C++控制台输出

Question

我一直在尝试将输出格式化为控制台的时间最长,并且没有发生任何事情.我一直在尝试尽可能多地使用iomanip和ofstream&out函数.

void list::displayByName(ostream& out) const
{
    node *current_node  = headByName;

    // I have these outside the loop so I don't write it every time.

    out << "Name\t\t" << "\tLocation" << "\tRating " << "Acre" << endl;
    out << "----\t\t" << "\t--------" << "\t------ " << "----" << endl;

    while (current_node)
    {
        out << current_node->item.getName() // Equivalent tabs don't work?
            << current_node->item.getLocation()
            << current_node->item.getAcres()
            << current_node->item.getRating()
            << endl;

        current_node = current_node->nextByName;
    }

    // The equivalent tabs do not work because I am writing names,
    // each of different length to the console. That explains why they
    // are not all evenly spaced apart.
}

他们可以使用什么来使它们彼此正确对齐？我正在调用的函数是不言自明的,并且所有长度都不同,因此彼此之间不能很好地对齐.

我已经尝试了所有的东西iomanip.

Answer 1

可以把它想象成使用Microsoft Excel :)您可以将您的流视为字段.因此,首先设置字段的宽度,然后在该字段中插入文本.例如:

#include <iostream>
#include <iomanip>
#include <string>

int main()
{
    using namespace std;

    string firstName = "firstName",
            secondName = "SecondName",
            n = "Just stupid Text";
    size_t fieldWidth = n.size(); // length of longest text

    cout << setw(fieldWidth) << left << firstName << endl // left padding
         << setw(fieldWidth) << left << secondName << endl
         << setw(fieldWidth) << left << n << endl;

    cout << setw(fieldWidth) << right << firstName << endl // right padding
         << setw(fieldWidth) << right << secondName << endl
         << setw(fieldWidth) << right << n << endl;
}

......

......

场宽只意味着宽度text + spaces.fill除了空格之外你还可以:

string name = "My first name";
cout << setfill('_') << setw(name.size() + 10) << left << name;

.....

output::
My first name__________

......

我认为最好的方法是找出你的格式然后,编写一个新的格式化程序来完成你想要的所有工作:

#include <iostream>
#include <iomanip>
#include <string>

std::ostream& field(std::ostream& o)
{
    // usually the console is 80-character wide.
    // divide the line into four fields.
    return o << std::setw(20) << std::right;
}

int main()
{
    using namespace std;

    string firstName = "firstName",
            secondName = "SecondName",
            n = "Just stupid Text";
    size_t fieldWidth = n.size();

    cout << field << firstName << endl
         << field << secondName << endl
         << field << n << endl;
}

如果你开始考虑参数化操纵器,只有那个接受一个int或long参数很容易实现,如果你不熟悉其他类型,其他类型真的很模糊C++.

Answer 2

Boost有一个格式库,允许您像旧的C printf()一样轻松地格式化输出,但是C++的类型安全.

请记住,旧的C printf()允许您指定字段宽度.如果输出尺寸过小,则此空间填充该字段(请注意,它不能处理超大字段).

#include <iostream>
#include <iomanip>
#include <boost/format.hpp>

struct X
{  // this structure reverse engineered from
   // example provided by 'Mikael Jansson' in order to make this a running example

    char*       name;
    double      mean;
    int         sample_count;
};
int main()
{
    X   stats[] = {{"Plop",5.6,2}};

    // nonsense output, just to exemplify

    // stdio version
    fprintf(stderr, "at %p/%s: mean value %.3f of %4d samples\n",
            stats, stats->name, stats->mean, stats->sample_count);

    // iostream
    std::cerr << "at " << (void*)stats << "/" << stats->name
              << ": mean value " << std::fixed << std::setprecision(3) << stats->mean
              << " of " << std::setw(4) << std::setfill(' ') << stats->sample_count
              << " samples\n";

    // iostream with boost::format
    std::cerr << boost::format("at %p/%s: mean value %.3f of %4d samples\n")
                % stats % stats->name % stats->mean % stats->sample_count;
}

Answer 3

您可以编写一个始终将相同数量的字符打印到标准输出的过程。

就像是：

string StringPadding(string original, size_t charCount)
{
    original.resize(charCount, ' ');
    return original;
}

然后在你的程序中这样使用：

void list::displayByName(ostream& out) const
{
    node *current_node  = headByName;

    out << StringPadding("Name", 30)
        << StringPadding("Location", 10)
        << StringPadding("Rating", 10)
        << StringPadding("Acre", 10) << endl;
    out << StringPadding("----", 30)
        << StringPadding("--------", 10)
        << StringPadding("------", 10)
        << StringPadding("----", 10) << endl;

    while ( current_node)
    {
        out << StringPadding(current_node->item.getName(), 30)
            << StringPadding(current_node->item.getLocation(), 10)
            << StringPadding(current_node->item.getRating(), 10)
            << StringPadding(current_node->item.getAcres(), 10)
            << endl;
        current_node = current_node->nextByName;
    }
}