How to create a macro in c with inside a String variable?-CodePudding

I have in the past defined in the macro in the following way..

#define MACRO_NAME "devices/987654/bucket"

I would like to replace the number with a String variable class String in c .

How can I define a new macro with inside with string ?

Thanks

CodePudding user response：

You cannot. Make it a String (I suppose this is arduino, otherwise you'd be using std::string):

const String string_name = String("devices/")   the_number   String("/bucket");

Macros are expanded by the preprocessor as the first step of compilation. At that stage there are no variables or strings, only token.

CodePudding user response：

You can do whatever you want by using a macro function. Here is a small example using std::string

#include <iostream>
#include <string>

#define MACRO_NAME(NUMBER, OUT){replaceNumber(NUMBER, OUT);}        

void replaceNumber(int32_t number, std::string &out){
    const std::string devices = "devices/";
    const std::string bucket = "/bucket";
    out = devices   std::to_string(number)   bucket;
}

int main()
{
    std::string name; 
    MACRO_NAME(213, name);
    std::cout << name << std::endl;
    return 0;
}