Rust

Rust / 07 Sep 2026 / 10 min read

Initialize Shared Rust State Once with OnceLock

Applications often need one shared value that is expensive or awkward to construct but should not change after initialization. Examples include parsed configuration, a lookup table, a compiled matcher, or metadata discovered during startup. A plain static works only when the value can be created as a constant. A Mutex<Option<T>> can represent “not initialized yet,” but it also introduces a lock and a mutable state model that the program may not need after setup.

Rust Concurrency

Rust / 03 Sep 2026 / 9 min read

Understand Pin and Unpin in Rust

Most Rust values can move freely. Assign a value to another variable, pass it by value, return it from a function, or replace it inside a container, and the value may end up at a different memory address. Usually that is exactly what you want. Rust’s ownership model tracks who owns a value, not where that value must remain in memory. A smaller class of types is different. Some values become address-sensitive: code relies on the value continuing to exist at the same memory location. Compiler-generated futures and carefully designed self-referential structures are common examples.

Rust Ownership

Rust / 02 Sep 2026 / 4 min read

Rust Iterator Ownership: iter, iter_mut, and into_iter

Rust iteration becomes much easier once iterator choice is connected to ownership. For a collection such as Vec<T>, the central question is whether the loop should borrow values, mutate them in place, or consume the collection. The common methods are iter(), iter_mut(), and into_iter(). Borrow with iter() iter() produces shared references: fn print_names(names: &[String]) { for name in names.iter() { println!("{name}"); } } Inside the loop, name has type &String.

Rust Iterators

Rust / 02 Sep 2026 / 6 min read

Recovering Safely from Poisoned Mutexes in Rust

A mutex protects shared data from concurrent access, but mutual exclusion alone does not guarantee that the data remains valid. A thread can panic halfway through a multi-step update and release the lock during unwinding, leaving the protected value in a state that other threads should not blindly trust. Rust’s standard Mutex records this situation through poisoning. A poisoned mutex is still lockable, but acquiring it returns an error that forces the caller to decide whether continuing is appropriate.

Rust Concurrency

Rust / 02 Sep 2026 / 4 min read

Interior Mutability in Rust with RefCell

Rust normally enforces borrowing at compile time: either one mutable reference or any number of immutable references may exist at a given moment. That rule prevents data races and many aliasing bugs before the program runs. Sometimes the compiler cannot prove that a safe mutation pattern is valid, even though the program can enforce the rule dynamically. RefCell<T> provides interior mutability for those cases by moving borrow checking from compile time to runtime.

Rust RefCell

Rust / 01 Sep 2026 / 3 min read

Use the Typestate Pattern to Make Invalid Rust States Unrepresentable

Many APIs have lifecycle rules: a connection must be opened before sending, a transaction must begin before committing, or a builder must receive required values before producing output. Runtime flags can enforce these rules, but Rust can sometimes encode them in types instead. The typestate pattern represents each valid state with a distinct type and makes transitions consume one state to produce another. Encode states as marker types use std::marker::PhantomData; struct Disconnected; struct Connected; struct Connection<State> { endpoint: String, _state: PhantomData<State>, } impl Connection<Disconnected> { fn new(endpoint: String) -> Self { Self { endpoint, _state: PhantomData } } fn connect(self) -> Connection<Connected> { Connection { endpoint: self.endpoint, _state: PhantomData, } } } impl Connection<Connected> { fn send(&self, payload: &[u8]) { println!("sending {} bytes", payload.len()); } } send does not exist for Connection<Disconnected>. Incorrect call ordering becomes a compile-time error instead of a branch in production.

Rust Typestate

Rust / 01 Sep 2026 / 5 min read

Practical Error Handling in Rust with Result and the ? Operator

Rust makes recoverable failure part of a function’s type. Instead of relying on exceptions, operations that can fail commonly return Result<T, E>, forcing callers to either handle the error or propagate it. That explicitness can feel verbose at first. The ? operator and well-designed error types keep the code concise without hiding failure paths. Result represents success or failure Result<T, E> has two variants: Ok(value) Err(error) Reading a file therefore returns either the file contents or an I/O error:

Rust Error Handling

Rust / 01 Sep 2026 / 5 min read

Choosing &str, String, and Cow for Rust Text APIs

Rust has several common ways to represent UTF-8 text, and choosing between &str, String, and Cow<'a, str> is fundamentally an ownership decision. The best API is usually the one that asks callers for the least ownership it needs and returns ownership only when the result requires it. Use &str when you only need to read text A string slice borrows UTF-8 text owned elsewhere: fn is_blank(value: &str) -> bool { value.trim().is_empty() } This accepts borrowed views into a String, string literals, and other string slices without taking ownership or allocating.

Rust Strings

Rust / 01 Sep 2026 / 4 min read

Borrowed or Owned Data in Rust API Design

Rust APIs frequently face a design choice that is more important than syntax: should a function borrow data from the caller or take ownership of it? Borrowing can avoid allocation and make reuse cheap. Ownership can simplify storage and decouple lifetimes. Good APIs use each where it matches the actual data flow. Borrow when work is temporary If a function only reads a string during the call, accepting &str is usually natural:

Rust Ownership

Rust / Updated 02 Sep 2025 / 3 min read

Understanding Structs and Methods in Rust

Structs are Rust’s primary way to group related values into a custom data type. They make data models explicit and can be paired with impl blocks to define methods and associated functions that belong with that data. What Is a Struct? A struct is a custom type that combines related fields into one logical value. Rust structs are often used for domain models, configuration, state, request data, and many other structured values.

Rust

Rust / Updated 02 Sep 2025 / 3 min read

Understanding Enums and Pattern Matching in Rust

Enums and pattern matching are central Rust features for representing a fixed set of possible states and handling each state explicitly. Rust enums can carry data, while match lets you destructure those values and choose behavior based on their shape. What Is an Enum in Rust? An enum defines a type whose value is exactly one of several variants. Unlike simple enumerations in some languages, Rust variants can also carry structured data.

Rust

Rust / Updated 02 Sep 2025 / 3 min read

Method Syntax in Rust

Rust methods define behavior associated with a type such as a struct or enum. They are usually declared inside an impl block and are called on a value with dot syntax. What Is a Method in Rust? A method is a function whose first parameter is some form of self, which represents the value the method is called on. Methods keep behavior close to the type it belongs to and often make APIs easier to read.

Rust

Rust / Updated 02 Sep 2025 / 3 min read

Working with Arrays in Rust

An array in Rust is a fixed-size collection whose elements all have the same type. Arrays are useful when the number of elements is known at compile time and should not grow or shrink during execution. What Is an Array in Rust? The type of an array includes both its element type and its length. For example, [i32; 5] is an array containing exactly five i32 values. A differently sized array is a different type.

Rust Array

Rust / Updated 02 Sep 2025 / 3 min read

Using Variables in Rust

Variables are one of the first Rust concepts to learn because Rust makes mutability, types, and ownership explicit. This guide covers variable declarations, mutable values, type annotations, constants, and shadowing. What Is a Variable in Rust? A variable binds a name to a value. Rust is statically typed, so the compiler knows the type of every variable at compile time and checks that operations use compatible types. Declare Variables Use let:

Rust

Rust / Updated 02 Sep 2025 / 3 min read

Using Functions in Rust

Functions are reusable blocks of code that help divide a program into smaller, focused pieces. Rust functions can accept typed parameters, return values, borrow data, and work with functions or closures as inputs. What Is a Function in Rust? Functions are declared with the fn keyword, followed by the function name, parameters, an optional return type, and a body: fn function_name(parameters) { // function body } Define and Call a Function fn main() { greet(); } fn greet() { println!("Hello, Rustacean!"); } Rust does not require a function to be defined before the call site in the source file, as long as it is visible in the current module.

Rust

Rust / Updated 02 Sep 2025 / 4 min read

Understanding References and Borrowing in Rust

References and borrowing let Rust code access data without taking ownership of it. These concepts are fundamental to Rust’s memory-safety model and allow programs to share and mutate data under rules that the compiler can verify. What Is a Reference in Rust? A reference points to a value owned elsewhere without becoming responsible for dropping that value. References use & syntax and are either immutable or mutable: Immutable reference (&T): allows read-only access. Mutable reference (&mut T): allows mutation while enforcing exclusive access rules. Immutable References Immutable references let a function inspect a value without consuming it:

Rust

Rust / Updated 02 Sep 2025 / 4 min read

Understanding Ownership in Rust

Ownership is one of Rust’s defining features. It lets Rust manage memory safely without a garbage collector by enforcing rules about who owns a value, when ownership moves, and when values are dropped. Understanding ownership is essential because it affects variable scope, function calls, references, borrowing, and many compiler errors you will encounter while learning Rust. What Is Ownership? Ownership is Rust’s model for managing resources. A value has an owner, and Rust can determine at compile time when that value is no longer needed. This design helps prevent problems such as use-after-free bugs, double frees, dangling references, and data races.

Rust

Rust / Updated 02 Sep 2025 / 3 min read

Understanding Control Flow in Rust

Control flow determines which parts of a program run and how often they run. Rust provides expressive control-flow constructs including if, match, loop, while, and for. Understanding these tools is essential for writing programs that make decisions, repeat work, and handle different states safely. What Is Control Flow? Control flow describes the order in which statements and expressions are evaluated. It lets a program choose between branches, repeat operations, and respond differently to values or conditions.

Rust