#static #lazy-evaluation #macro #getter-setter


Attach values statically to a type using static get/set methods

8 releases

0.3.4 Dec 29, 2023
0.3.3 Dec 27, 2023
0.2.1 Nov 12, 2023
0.1.1 Sep 10, 2023
0.1.0 Aug 30, 2023

#413 in Rust patterns

33 downloads per month
Used in bevy_cell


649 lines

Macro to 'attach' values statically to a type using static getter and setter methods.

type_cell = "0.3"
use type_cell::*;

        [lazy_str.clone() -> String {"hello"}]
    {bool > Vec<bool>} 

fn main(){
        "hello world",
        &format!("{} {}",&String::lazy_str(),String::nice_str())

🧱 Basic Usage

  • Use the macro: tycell!{...}
  • Which type should the value be 'attached' on? u32 {...}
  • Which type does the value have? static u32:
    • Which settings will it use?
      🌟 once_read Set it once. Get it read-only! (combine with Mutex/RwLock/... for mutability)
      🏁 once_write Set it once. Get it mutable, but risk race conditions! (be sure you win the race!)
      🦥 lazy_read Like once_read but set lazy inside the macro!
      👹 lazy_writeLike once_write but set lazy inside the macro!!
    • examples: static u32: once_read; or static String: lazy_read;
  • What's the name of the default setter method? set_type()
  • What's the name of the default getter method? get_type()
// Basic Usage 
tycell!{ bool {
    static Vec<bool>: once_read;
    set set_vec();
    get vec();
// Set it somewhere once:
// Get it anywhere afterwards:

The default setter parameter is a dynamic Into<..> and will use .into().
This means in this example you could also set it like this:


⚗ Advanced Usage

Multiple Setter and Getter with different parameters and return types can be defined!
There are two ways of doing it:

  • Methods:
    • Use inline methods for simple conversions!
    • set set_bool(Option<usize>): do.is_some();
    • get get_bool() -> bool: static.clone();
  • Function:
    • Use a function with correct parameters/return types and is accessible in the same file!
    • Use = before the function meta!
    • set =set_base_fn(a:Option<usize>);
    • get =get_base_fn() -> bool;
// Advanced Usage 
fn set_by_function (a:Option<usize>) -> bool {a.is_some()}
fn get_by_function (a:&bool) -> bool {a.clone()}
tycell!{ bool {
    static bool: once_read;
    set set_raw();
    set set_by_methods(Option<usize>): do.is_some();
    set =set_by_function(a:Option<usize>);
    get get_raw();
    get get_by_methods() -> bool: static.clone();
    get =get_by_function() -> bool;

Methods with parameters are supported in two different ways:

  • Constants:
    • Using = before a constant value!
    • set set_number(u32): do.clamp(=0,=100);
    • get get_number() -> bool: static.clamp(=0,=100);
  • Pass Through:
    • Naming the values with its types will pass it into the function!
    • set set_number(u32): do.clamp(min:u32,max:u32);
    • get get_number() -> bool: static.clamp(min:u32,max:u32);
// Advanced Usage 
tycell!{ u32 {
    static u32: once_read;
    set set_raw();
    set set_by_methods(u32): do.clamp(=0,=100);
    set set_pass(u32): do.clamp(min:u32,max:u32);
    get get_raw();
    get get_by_methods() -> u32: static.add(=5);
    get get_pass() -> u32: static.add(val:u32);
// Sets value to 1000.clamp(0,123) = 123
// Gets 123.add(5) = 128

🧊 Constant

You can also set const values!

// Constant
tycell!{ u32 {
    const u32 = 100;
    get number();
// Gets 10!

👹 Risky Mutable Options

Only use this if you're sure there are no race conditions (or they don't matter) or for debug purposes!
To make the static value mutable, use once_write or lazy_write.

// Risky Mutable
tycell!{ u32 {
    static u32: risky_write;
    set set_number();
    get number();
// Set it somewhere once:
// Default getter is mutable already
*u32::number() = 10;
// Gets 10!

🦥 As Lazy Static

To create a lazy static value, use the lazy_read option and use a block instead of the setter function!

// Lazy Static
tycell!{ u32 {
    static HashMap<u32,String>: lazy_read;
    set {
        let mut map = HashMap::new();
        for i in 0..100 {
    get get_lazy_map();
    get get_lazy() -> Option<&String>: static.get(id:&u32);
// Gets Some("3":&String)

➡ Simple Mapping

If you only need the default getter and setters, there is a short form:

// Simple Usage
    // store a vec of bools on the bool type
    // a single specifier inside [..] will use once_read
    // adding 'mut' before it sets it to once_write
    // adding a block {} after the specifier will use lazy_.. instead of once_..
    bool > Vec<bool>: [bools] [mut more_bools] [lazy_bools{vec![true,false]}];
    // adding '= value' after the specifier will set a constant value
    bool > u32: [number=100];

If you only attach values of the same type as their parent:

// Simplest Usage
    // Same as bool > bool: [is_nice];
    bool: [is_nice];

If you want to attach a type to its single generic type, e.g. u32 > Vec<u32> you can use !Vec<u32>.
Increase the number of ! to set the level, e.g. u32 > Vec<Vec<u32>> <=> !!Vec<Vec<u32>>.


You can't mix different types of left-handed syntax, unless wrapped in {}

// working
    {!Vec<bool>} [is_nice]
    {bool>Vec<bool>} [is_v_nice]
    {bool} [is_x_nice]
// NOT working
    !Vec<bool>: [is_nice];
    bool>Vec<bool>: [is_v_nice];
    bool: [is_x_nice];

You can also chain methods for the getter and adjust its return type.


➡ Simple (Hash)Maps and Vecs

Ease up getting values from a HasmMap-esque types, by using after the name.
if no key is provided, the type is set to a Vec<..> instead.

// uses anythng named TyMap for flaxibility
use std::collections::HashMap as TyMap;
    // same as above, but <keytype> after the specifier
    bool > bool: [bools<u8>] [mut more_bools<u8>] [lazy_bools<u8>{[(1,true)]}];
  • bevy_cell - Attach bevy Handle and Entity to types.


Licensed under either of Apache License, Version 2.0 or MIT license at your option.
Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in this crate by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.