C++ How do I Split a C string into 2 variables

[remote stratus]

Right now I'm trying to figure out how to split a cstring by a space via a loop. I'm not exactly sure on how to do it.
This is a really rough example of what I'm trying to do rn (I know this isn't a full fuctional code this is just a really rough example of what I'm doing or trying to do)

struct()
{
char first[15] // Issue is trying to split the first variable at the space to set it into this variable
char second[15] // then trying to to set the 2nd word.
}
int main()
{
char fullname[15] = "John Doe";
}

I'm trying to initialize the two words into the structure by splitting the name can anyone give me a explaination on how I would do that?

[glacial sorrel]

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[remote stratus]

C++ How do I Split a C string into 2 variables

[bold pawn]

;compile

#include <string>
#include <stdexcept>
#include <iostream>

struct Person
{
    Person(const std::string &fullname)
    {
        const auto space_pos = fullname.find(' ');
        if (space_pos == std::string::npos)
        {
            throw std::runtime_error("Fullname with no space!");
        }
        
        firstname = fullname.substr(0, space_pos);
        surname = fullname.substr(space_pos + 1);
    }

    std::string firstname;
    std::string surname;
};

int main()
{
    const Person p("John Doe");
    std::cout << "First name = " << p.firstname << '\n';
    std::cout << "Surname = " << p.surname << '\n';
}

[fierce granite]

Program Output

First name = John
Surname = Doe

repkows#7154 | 46ms | c++ | x86-64 gcc 12.2 | godbolt.org

[remote stratus]

I'm like looking at this and like don't really understand much of it

[bold pawn]

Okay lets go bit by bit. Do you understand all of main() ?

[remote stratus]

Main yeah I understand that alright

Is within the structure where is like kinda confusing me

I think mainly because what you put is something I haven't learned yet

[bold pawn]

Are you familiar with std::string?

[remote stratus]

yes

[bold pawn]

Okay so a Person is just a struct with two data members firstname and surname

The function in the struct Person called Person(const std::string& fullname) is a special type of function called a constructor. The purpose of a constructor is to 'construct' a type.

It's job is basically to make sure that the struct starts off in a good, valid state

With me so far?

[remote stratus]

yeah I'd say the part that throws me off the most is like runtime_error and substr

[bold pawn]

Ok I'll go through the constructor line by line

[remote stratus]

k

[bold pawn]

const auto space_pos = fullname.find(' ');

fullname is a std::string. std::string has a function you can call called find() who takes in a character or string and returns the index of its position

Im just setting space_pos to the index of ' ' in fullname

if (space_pos == std::string::npos)
{
    throw std::runtime_error("Fullname with no space!");
}

To write good code we should now be a good programmer and check that the string we were given (fullname) actually contained a space. If it didn't then things get weird, is the fullname just the firstname, or maybe just the lastname? we don't know so we essentially give up

[remote stratus]

ah

[bold pawn]

So if we were given a fullname with no space the program will TERMINATE

[remote stratus]

I see

[bold pawn]

firstname = fullname.substr(0, space_pos);
surname = fullname.substr(space_pos + 1);

These lines are all about initializing our two data members. substr() (like find()) is a function you can call on any std::string. Its job is to create a new string from a 'sub-string' of fullname.

So the firstname is being set to the characters from index 0 (the start) all the way to just before the space_pos

the surname is being set from all the characters one after the position of the space

[remote stratus]

Aight I think I understand.

Ye I haven't gone that far into coding yet and haven't taught some of the things you said within my class yet. Still tryna get the hang of it

[bold pawn]

By the end of your class you should understand it

The main two things that are probably new for you to remember are constructors and exceptions

[remote stratus]

Ok

[bold pawn]

Google those words if you want to learn more. If they're teaching you c++ in class you'll learn these soon

[remote stratus]

ye for sure

I'm pretty sure most we covered so far is structures. And going over the broader things on how to do stuff in C++

We haven't gotten to much into the smaller details yet.

vectors, arrays, structures, strings and loops is what I been taught so far

But thanks for your help tho

👍

[glacial sorrel]

Thank you and let us know if you have any more questions!

[bold pawn]

I'd recommend you use std::string as much as your teacher lets you. Don't use c-style strings like const char* my_string = "Hello!"; or char my_name[40];

[remote stratus]

kk

whats the issue with those kind of c-style strings?

Is it just inefficient in the sense of it being redundant code that could be simpler or what

[bold pawn]

It prevents you from writing a whole host of bugs. Its because to use C-style arrays properly you need to understand pointers and memory management; those topics and beginners don't mix well together.

[remote stratus]

I'll keep that in mind. At the same time not like I can really avoid using pointers when I'm being told to use them.