Indentation level management in C Logger class-CodePudding

I want to build a printer class that co-manages the indentation level automatically by an Indentation level destructor.

However, this code uses a static indentation level, it works well for a single instance. What workaround I can make to make a unique indentation level across several instances?

#include <stdio.h>
#include <string>
class Logger
{
  std::string _tag;
protected:
public:
  class Indents
  {
  public:
     Indents () { indents  ; };
    ~Indents () { indents--; };
  };
  static int indents;
  Logger (const std::string & tag):_tag (tag)
  {
  }
  void I (const std::string & info)
  {
    for (int i = 0; i < indents; i  ) 
        printf ("\t"); 

    printf ("%s:\t", _tag.c_str());
    printf ("%s\n", info.c_str());
  }
};

int Logger::indents = 0;
Logger x ("Service X");
int main ()
{
  {
    auto a = Logger::Indents();
    x.I ("Hello");
  }
  x.I ("World");

  return 0;
}

Prints:

    Service X:  Hello  
Service X:  World

CodePudding user response：

you capture the Logger instance to Indents. (and change Logger::indents to non-static)

class Logger{
   int indents = 0; // no more static

   public:
   struct Indents{
       Indents (Logger& logger):logger(logger) { logger.indents  ; };
      ~Indents () { logger.indents--; };
      Logger& logger;
   };
};

then you can either directly use it

void foo(){
   Logger x;
   Logger::Indents indent{x};
}

or write a member function to return it

class Logger{
   // ...
   Indents indent(){return {*this};}
};

// use
void foo(){
   Logger x;
   auto indent = x.indent();
}