C++ 字符串格式化方法

最近用C++写代码的时候,发现C++居然没有自己的字符串格式化的方法(PS:C++20才推出了自己format),所以如果不支持C++20,就没有现成的用,在网上找了一圈,发现了某位大神自己写的C++字符串格式化的工具,就是一个Format.h头文件,可以直接用,很方便

Github地址:https://github.com/arajar/format

Format.h具体代码如下

#pragma once

#include <string>
#include <vector>
#include <stdlib.h>
#include <iostream>
#include <algorithm>
#include <sstream>
#include <iomanip>

namespace util
{
	class ArgBase
	{
	public:
		ArgBase() {}
		virtual ~ArgBase() {}
		virtual void Format(std::ostringstream &ss, const std::string& fmt) = 0;
	};

	template <class T>
	class Arg : public ArgBase
	{
	public:
		Arg(T arg) : m_arg(arg) {}
		virtual ~Arg(){}
		virtual void Format(std::ostringstream &ss, const std::string& fmt)
		{
			ss << m_arg;
		}
	private:
		T m_arg;
	};

	class ArgArray : public std::vector < ArgBase* >
	{
	public:
		ArgArray() {}
		~ArgArray()
		{
			std::for_each(begin(), end(), [](ArgBase* p){ delete p; });
		}
	};

	static void FormatItem(std::ostringstream& ss, const std::string& item, const ArgArray& args)
	{
		int index = 0;
		int alignment = 0;
		std::string fmt;

		char* endptr = nullptr;
		index = strtol(&item[0], &endptr, 10);
		if (index < 0 || index >= args.size())
		{
			return;
		}

		if (*endptr == ',')
		{
			alignment = strtol(endptr + 1, &endptr, 10);
			if (alignment > 0)
			{
				ss << std::right << std::setw(alignment);
			}
			else if (alignment < 0)
			{
				ss << std::left << std::setw(-alignment);
			}
		}

		if (*endptr == ':')
		{
			fmt = endptr + 1;
		}

		args[index]->Format(ss, fmt);

		return;
	}

	template <class T>
	static void Transfer(ArgArray& argArray, T t)
	{
		argArray.push_back(new Arg<T>(t));
	}

	template <class T, typename... Args>
	static void Transfer(ArgArray& argArray, T t, Args&&... args)
	{
		Transfer(argArray, t);
		Transfer(argArray, args...);
	}

	template <typename... Args>
	std::string Format(const std::string& format, Args&&... args)
	{
		if (sizeof...(args) == 0)
		{
			return format;
		}

		ArgArray argArray;
		Transfer(argArray, args...);
		size_t start = 0;
		size_t pos = 0;
		std::ostringstream ss;
		while (true)
		{
			pos = format.find('{', start);
			if (pos == std::string::npos)
			{
				ss << format.substr(start);
				break;
			}

			ss << format.substr(start, pos - start);
			if (format[pos + 1] == '{')
			{
				ss << '{';
				start = pos + 2;
				continue;
			}

			start = pos + 1;
			pos = format.find('}', start);
			if (pos == std::string::npos)
			{
				ss << format.substr(start - 1);
				break;
			}

			FormatItem(ss, format.substr(start, pos - start), argArray);
			start = pos + 1;
		}

		return ss.str();
	}
}

使用方法

#include <iostream>
#include "Format.h"

int main()
{
	std::string format_str = util::Format("There are {0} fools in the world",10);
	std::cout << format_str << std::endl;

	return 0;
}