How to Use string_view in C++: Syntax and Examples

Use std::string_view to create a lightweight, non-owning reference to a string or part of a string without copying data. It is declared like std::string_view sv = "text"; and can be used to read or pass strings efficiently.

Syntax

std::string_view is a class that holds a pointer to a string and its length without owning the string data. You can create it from string literals, std::string, or character arrays.

Basic syntax:

• std::string_view sv = "hello"; — from string literal
• std::string s = "world"; std::string_view sv = s; — from std::string
• std::string_view sv(data, length); — from pointer and length

cpp

std::string_view sv1 = "hello";
std::string s = "world";
std::string_view sv2 = s;
const char* data = "example";
std::string_view sv3(data, 4); // "exam"

Example

This example shows how to create std::string_view from different sources and use it to print parts of strings without copying.

cpp

#include <iostream>
#include <string>
#include <string_view>

int main() {
    std::string_view sv1 = "Hello, world!"; // from literal
    std::string s = "C++ string";
    std::string_view sv2 = s; // from std::string

    const char* cstr = "example text";
    std::string_view sv3(cstr, 7); // first 7 chars

    std::cout << sv1 << "\n";
    std::cout << sv2 << "\n";
    std::cout << sv3 << "\n";

    return 0;
}

Output

Hello, world!
C++ string
example

Common Pitfalls

Beware: std::string_view does not own the string data it points to. If the original string is destroyed or goes out of scope, the string_view becomes invalid and using it causes undefined behavior.

Also, modifying the original string while a string_view exists can cause unexpected results.

cpp

#include <iostream>
#include <string>
#include <string_view>

int main() {
    std::string_view sv;
    {
        std::string temp = "temporary";
        sv = temp; // sv points to temp's data
    } // temp is destroyed here
    // sv now points to invalid memory
    // std::cout << sv << "\n"; // Undefined behavior!
    return 0;
}

Quick Reference

• std::string_view is a non-owning view of a string.
• It stores a pointer and length, no copying of string data.
• Safe only if original string outlives the view.
• Useful for efficient read-only string access and function parameters.

Key Takeaways

Use std::string_view to refer to strings without copying data for better performance.

Always ensure the original string outlives the string_view to avoid invalid references.

You can create string_view from literals, std::string, or raw pointers with length.

string_view is read-only and does not manage string memory.

Avoid modifying the original string while a string_view exists to prevent bugs.