Auto generate id

[umairbilal]

Auto generate id

  Hello everyone !
I'm new here.
I'm trying to auto generate unique id for every patient who register in hospital management system.
So kindly help me with that.
Thank you so much. 

[JLBorges]

Something like this, perhaps:

#include <iostream>
#include <string>

struct patient {

    std::string name ;
    // ...

    unsigned long long id = ++last_assigned_id ;

    static unsigned long long last_assigned_id ;
};

unsigned long long patient::last_assigned_id = 1000 ;

int main()
{
    const patient some_patients[] = { { "tom" }, { "dick" }, { "harry" } } ;

    for( const patient& p : some_patients )
        std::cout << p.id << ". " << p.name << '\n' ;
}

http://coliru.stacked-crooked.com/a/d51ae5272b163bbe

[umairbilal]

Thanks JLBorges it helped me
But the problem is I need to apply this in File Handling where it should read the file and increment id by 1 each time when new patient is added.

[Enoizat]

Hi, umairbilal. If you can, speak by code: your question is not clear. JLBorges’s solution is a generic one: it fits nearly everywhere. Please, post a compilable example of what you’re trying to do to get better answers.

…in File Handling where it should read the file and increment id by 1 each time when new patient is added.

When you read a file, you do not add data; if you’re adding data, you’re writing into the file. Please explain.

And please specify if it is an assignment (I presume it is).

[JLBorges]

> read the file and increment id by 1 each time when new patient is added.

#include <string>
#include <fstream>

struct patient {

    std::string name ;
    // ...

    unsigned long long id = next_id() ;

    // path to file to store the last generated id
    static constexpr char id_file_name[] = "last_generated_unique_id.txt" ;

    static unsigned long long next_id( unsigned long long default_id = 1001 ) {
        
        unsigned long long id ;

        {
            // try to read from the last id from file;
            // if successful, increment the id to get the next unique id
            // otherwise, fall back to the default id 
            // (robust error reporting/handling elided for brevity)
            std::ifstream file(id_file_name) ;
            if( file >> id ) ++id ;
            else id = default_id ;
        }

        // update the file with the freshly generated id
        // (error handling elided for brevity)
        std::ofstream(id_file_name) << id << '\n' ;

        return id ;
    }
};

[umairbilal]

Thank you so much
You people are very helping and very nice people .
I got my problem solved.
Enoizat , yes it was an assignment.
😇😇😊😊