What is string_view in C++: Explanation and Usage

string_view in C++ is a lightweight, non-owning reference to a sequence of characters, allowing you to view strings without copying them. It provides a fast and efficient way to read or process strings without managing their memory.

How It Works

Imagine you have a book and you want to show a friend a specific page without giving them the whole book. string_view works similarly by pointing to a part of a string without copying it. It just remembers where the string starts and how long it is.

This means string_view does not own the string data; it only views it. Because it doesn't copy the string, it is very fast and uses less memory. However, you must be careful that the original string stays alive while the string_view is used, or else it will point to invalid data.

Example

This example shows how to create a string_view from a string and use it to print part of the string without copying it.

cpp

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

int main() {
    std::string text = "Hello, world!";
    std::string_view view(text.data() + 7, 5); // points to "world"

    std::cout << "Original string: " << text << '\n';
    std::cout << "String view: " << view << '\n';

    return 0;
}

Output

Original string: Hello, world!
String view: world

When to Use

Use string_view when you want to read or process parts of strings quickly without copying data. It is especially useful in functions that take string input but do not need to modify or own the string.

For example, parsing text, searching substrings, or passing string data between functions can benefit from string_view. It reduces memory use and improves speed by avoiding unnecessary copies.

Key Points

• Non-owning: string_view does not manage string memory.
• Efficient: No copying means faster and less memory use.
• Safe use: Original string must stay valid while string_view is used.
• Read-only: You cannot modify the string through string_view.

Key Takeaways

string_view is a fast, non-owning reference to string data.

It avoids copying strings, improving performance and memory use.

Always ensure the original string outlives the string_view.

string_view is ideal for read-only string access and parsing.

It cannot modify the underlying string data.