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* Update string-slices.md * Adding an extra example of converting `String` back to `&str`. * C++ who would often read this guide could get immediate intuitive understanding of Rust strings if you compare them to C++ equivalents. * Expand on `String` vs `std::string` Co-authored-by: Martin Geisler <martin@geisler.net>
43 lines
1.4 KiB
Markdown
43 lines
1.4 KiB
Markdown
# `String` vs `str`
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We can now understand the two string types in Rust:
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```rust,editable
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fn main() {
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let s1: &str = "World";
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println!("s1: {s1}");
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let mut s2: String = String::from("Hello ");
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println!("s2: {s2}");
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s2.push_str(s1);
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println!("s2: {s2}");
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let s3: &str = &s2[6..];
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println!("s3: {s3}");
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}
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```
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Rust terminology:
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* `&str` an immutable reference to a string slice.
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* `String` a mutable string buffer.
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<details>
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* `&str` introduces a string slice, which is an immutable reference to UTF-8 encoded string data stored in a block of memory. String literals (`”Hello”`), are stored in the program’s binary.
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* Rust’s `String` type is a wrapper around a vector of bytes. As with a `Vec<T>`, it is owned.
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* As with many other types
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* `String::from` creates a string from a string literal; `String::new` creates a new empty string, to which string data can be added using the `to_string` method.
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* The `push_str` method appends a string slice to the string.
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* You can borrow `&str` slices from `String` via `&` and optionally range selection.
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* For C++ programmers: think of `&str` as `const char*` from C++, but the one that always points
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to a valid string in memory. Rust `String` is a rough equivalent of `std::string` from C++ (main difference: it can only contain UTF-8 encoded bytes and will never use a small-string optimization).
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</details>
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