So, I am working through the Rust Programming Language, google, chatGPT, and still think I understand about 70% here:
The String type is for variables with a string that can mutate, grow and shrink.
The &str type is a literal, but really a slice
The &String type is a reference to a String
The str type I haven’t found yet
So I feel I am missing something still. Why the two types, and the two references, when in the end it is all about strings or references to strings?
&str is not analogous to a slice.
str is a string slice, so
&str is a reference to a string slice.
ah, there you go. So, why would one use a reference to a slice [..] or a reference to a String? I do think I kind of understand it, but I want to make sure I fully understand it, so my apologies if I am asking the stupid questions here!
str is what is known as a DST (Dynamically Sized Type) or "Unsized" type (you might want to research about the
Sized trait if you want to know more on the subject). In order to store a variable, the compiler needs to know how much memory it needs for it; by definition, this task is not possible with DSTs, so we need to put them behind a pointer (&, Rc, Arc, etc.) so that the compiler uses the size of the pointer instead.
&String, as a rule of thumb you can consider it an anti-pattern. Its use cases are so scarce that in 99% of the cases it's most likely that the user wanted a
&str instead, so much so that the compiler can auto dereference the former into the latter.
Thank you, I think I get it!
No. String literals have type
&'static str, but not all
&strs are literals.
Here's a recent post summarizing slices (including
str), and another diagraming the difference between
&[_] (which is the same as the difference between
This post is a repost from another recent thread .
My favourite beginner article about strings, cleverly disguised as being about Fizz-Buzz:
This topic was automatically closed 90 days after the last reply. We invite you to open a new topic if you have further questions or comments.