rust | 易学教程

go 和 rust 设计模式对比

阅读更多关于 go 和 rust 设计模式对比

定义工厂模式可分为三类：简单工厂模式工厂方法模式抽象工厂模式简单工厂模式属于创建型模式，不属于 23 种 GOF 设计模式之一，由一个工厂对象决定创建出哪一种产品类实例，逻辑为定义一个工厂类，根据传入的参数不同返回不同的产品实例，被创建的实例具有共同的父类或接口。工厂方法模式跟简单工厂模式的区别就是，定义了一些工厂子类，每个工厂子类都可以创建相对应的产品类实例，而不用工厂父类去根据参数创建，一般在产品类比较多的情况下，不想太多复杂的逻辑封装在工厂父类里面，可以用这种模式。抽象工厂模式顾名思义，把工厂抽象出来，根据具体的业务需求组合工厂创建产品实例的逻辑，通常为创建多个产品实例类。抽象工厂一旦要增加创建产品实例的逻辑，就需要修改抽象工厂接口的具体产品组合逻辑，所以并不符合开闭原则，如果是需要频繁增加（修改）产品实例的话，要衡量是否采用这种模式基本结构工厂模式从源码上总的来说可以分为 4 部分：抽象产品：通过声明接口（特性），定义了产品的业务方法。具体产品：通过 implement 接口（特性），定义了业务方法的具体逻辑。抽象工厂：按照相应的业务逻辑，声明了创建产品对象的业务方法（多数为组合方式）。具体工厂：通过 implement 接口（特性），定义了创建产品对象的具体逻辑。结构设计的关键点：产品只负责产品对象的创建，其他什么都不关心，

How to efficiently push displayable item into String? [duplicate]

阅读更多关于 How to efficiently push displayable item into String? [duplicate]

问题 This question already has an answer here : How can I append a formatted string to an existing String? (1 answer) Closed 3 years ago . See this example: fn concat<T: std::fmt::Display>(s: &mut String, thing: T) { // TODO } fn main() { let mut s = "Hello ".into(); concat(&mut s, 42); assert_eq!(&s, "Hello 42"); } I know that I can use this: s.push_str(&format!("{}", thing)) but this is not the most efficient, because format! allocate a String that is not necessary. The most efficient is to

Capture all Regex matches into a vector

阅读更多关于 Capture all Regex matches into a vector

问题 I'd like to capture all the numbers in a string and return a vector of integers, something like this (the result can be an empty vector): fn str_strip_numbers(s: &str) -> Vec<isize> { unimplemented!() } A Python prototype: def str_strip_numbers(s): """ Returns a vector of integer numbers embedded in a string argument. """ return [int(x) for x in re.compile('\d+').findall(s)] For "alfa" the result is [] , for "42by4" it is [42, 4] . What is the idiomatic way to get it in Rust? UPD: fn str

How to return concrete type from generic function?

阅读更多关于 How to return concrete type from generic function?

问题 In the example below the Default trait is used just for demonstration purposes. My questions are: What is the difference between the declarations of f() and g() ? Why g() doesn't compile since it's identical to f() ? How can I return a concrete type out of a impl trait generically typed declaration? struct Something { } impl Default for Something { fn default() -> Self { Something{} } } // This compiles. pub fn f() -> impl Default { Something{} } // This doesn't. pub fn g<T: Default>() -> T {

Rust serde deserializing a mixed array

阅读更多关于 Rust serde deserializing a mixed array

问题 In Rust i am receiving data from a websocket. For simplicity it looks like this: [1, {"a": ["1.2345", 5, "9.8765"]}] The string i get from the websocket is indeed double-quoted 'floating point values' (thus in actuality strings), and unquoted integers. I want to deserialize this object into a struct. But since the return array "a" is of mixed type, I can't use something like: struct MyStruct { id: i32, a: [f64; 3], } So I thought let's define another struct: struct Ask { price: f64, whole_lot

How to run multiple futures that call thread::sleep in parallel? [duplicate]

阅读更多关于 How to run multiple futures that call thread::sleep in parallel? [duplicate]

问题 This question already has answers here : Why does Future::select choose the future with a longer sleep period first? (1 answer) What is the best approach to encapsulate blocking I/O in future-rs? (1 answer) Closed 2 years ago . I have a slow future that blocks for 1 second before running to completion. I've tried to use the join combinator but the composite future my_app executes the futures sequentially: #![feature(pin, futures_api, arbitrary_self_types)] extern crate futures; // v0.3 use

“invalid type: map, expected a sequence” when deserializing a nested JSON structure with Serde

阅读更多关于 “invalid type: map, expected a sequence” when deserializing a nested JSON structure with Serde

问题 I am trying to poll the GitHub API for issues and print them out. To do so, I need to deserialize a nested JSON structure that I receive from a cURL GET request. I am trying to get the url for all the objects in the items array: { "total_count": 4905, "incomplete_results": false, "items": [ { "url": "https://api.github.com/repos/servo/saltfs/issues/789", "repository_url": "https://api.github.com/repos/servo/saltfs", "labels_url": "https://api.github.com/repos/servo/saltfs/issues/789/labels{

“invalid type: map, expected a sequence” when deserializing a nested JSON structure with Serde

阅读更多关于 “invalid type: map, expected a sequence” when deserializing a nested JSON structure with Serde

Does rustc / cargo have a -march=native equivalent?

阅读更多关于 Does rustc / cargo have a -march=native equivalent?

问题 I feel like binary portability isn't really a concern, and so something like -march=native may always be the default behavior. I can't find anything saying one way or the other though. 回答1: As mentioned in the comments, pass the -C target-cpu option to rustc: rustc -C target-cpu=native For more options: $ rustc -C help ... -C target-cpu=val -- select target processor (rustc --print target-cpus for details) ... See How to pass rustc flags to cargo? for more methods of passing the option. I

Is it possible to modify the case of a token inside of a macro?

阅读更多关于 Is it possible to modify the case of a token inside of a macro?

问题 I am writing a macro which creates a struct managing user input. I am using the crates bitflags and sdl2. Return is an example for the key Return . This macro takes a list of all possible inputs and then ($($flag:ident = $value:expr;)+) => { ... } Creates a new bitflag with the name of the input bitflags!( struct KeyType: u64 { $( const $flag = $value;// UPPER_CASE is the norm for globals: 'RETURN' )+ } ); Checks if the key is pressed, using the Keycode enum. match event { $(Event::KeyDown {