bevy/examples/ecs/dynamic.rs
Periwink 3a664b052d
Separate component and resource access (#14561)
# Objective

- Fixes https://github.com/bevyengine/bevy/issues/13139
- Fixes https://github.com/bevyengine/bevy/issues/7255
- Separates component from resource access so that we can correctly
handles edge cases like the issue above
- Inspired from https://github.com/bevyengine/bevy/pull/14472

## Solution

- Update access to have `component` fields and `resource` fields

## Testing

- Added some unit tests
2024-08-06 01:19:39 +00:00

270 lines
9.7 KiB
Rust

#![allow(unsafe_code)]
//! This example show how you can create components dynamically, spawn entities with those components
//! as well as query for entities with those components.
use std::{alloc::Layout, io::Write, ptr::NonNull};
use bevy::prelude::*;
use bevy::{
ecs::{
component::{ComponentDescriptor, ComponentId, ComponentInfo, StorageType},
query::QueryData,
world::FilteredEntityMut,
},
ptr::{Aligned, OwningPtr},
utils::HashMap,
};
const PROMPT: &str = "
Commands:
comp, c Create new components
spawn, s Spawn entities
query, q Query for entities
Enter a command with no parameters for usage.";
const COMPONENT_PROMPT: &str = "
comp, c Create new components
Enter a comma separated list of type names optionally followed by a size in u64s.
e.g. CompA 3, CompB, CompC 2";
const ENTITY_PROMPT: &str = "
spawn, s Spawn entities
Enter a comma separated list of components optionally followed by values.
e.g. CompA 0 1 0, CompB, CompC 1";
const QUERY_PROMPT: &str = "
query, q Query for entities
Enter a query to fetch and update entities
Components with read or write access will be displayed with their values
Components with write access will have their fields incremented by one
Accesses: 'A' with, '&A' read, '&mut A' write
Operators: '||' or, ',' and, '?' optional
e.g. &A || &B, &mut C, D, ?E";
fn main() {
let mut world = World::new();
let mut lines = std::io::stdin().lines();
let mut component_names = HashMap::<String, ComponentId>::new();
let mut component_info = HashMap::<ComponentId, ComponentInfo>::new();
println!("{}", PROMPT);
loop {
print!("\n> ");
let _ = std::io::stdout().flush();
let Some(Ok(line)) = lines.next() else {
return;
};
if line.is_empty() {
return;
};
let Some((first, rest)) = line.trim().split_once(|c: char| c.is_whitespace()) else {
match &line.chars().next() {
Some('c') => println!("{}", COMPONENT_PROMPT),
Some('s') => println!("{}", ENTITY_PROMPT),
Some('q') => println!("{}", QUERY_PROMPT),
_ => println!("{}", PROMPT),
}
continue;
};
match &first[0..1] {
"c" => {
rest.split(',').for_each(|component| {
let mut component = component.split_whitespace();
let Some(name) = component.next() else {
return;
};
let size = match component.next().map(str::parse) {
Some(Ok(size)) => size,
_ => 0,
};
// Register our new component to the world with a layout specified by it's size
// SAFETY: [u64] is Send + Sync
let id = world.init_component_with_descriptor(unsafe {
ComponentDescriptor::new_with_layout(
name.to_string(),
StorageType::Table,
Layout::array::<u64>(size).unwrap(),
None,
)
});
let Some(info) = world.components().get_info(id) else {
return;
};
component_names.insert(name.to_string(), id);
component_info.insert(id, info.clone());
println!("Component {} created with id: {:?}", name, id.index());
});
}
"s" => {
let mut to_insert_ids = Vec::new();
let mut to_insert_data = Vec::new();
rest.split(',').for_each(|component| {
let mut component = component.split_whitespace();
let Some(name) = component.next() else {
return;
};
// Get the id for the component with the given name
let Some(&id) = component_names.get(name) else {
println!("Component {} does not exist", name);
return;
};
// Calculate the length for the array based on the layout created for this component id
let info = world.components().get_info(id).unwrap();
let len = info.layout().size() / std::mem::size_of::<u64>();
let mut values: Vec<u64> = component
.take(len)
.filter_map(|value| value.parse::<u64>().ok())
.collect();
values.resize(len, 0);
// Collect the id and array to be inserted onto our entity
to_insert_ids.push(id);
to_insert_data.push(values);
});
let mut entity = world.spawn_empty();
// Construct an `OwningPtr` for each component in `to_insert_data`
let to_insert_ptr = to_owning_ptrs(&mut to_insert_data);
// SAFETY:
// - Component ids have been taken from the same world
// - Each array is created to the layout specified in the world
unsafe {
entity.insert_by_ids(&to_insert_ids, to_insert_ptr.into_iter());
}
println!("Entity spawned with id: {:?}", entity.id());
}
"q" => {
let mut builder = QueryBuilder::<FilteredEntityMut>::new(&mut world);
parse_query(rest, &mut builder, &component_names);
let mut query = builder.build();
query.iter_mut(&mut world).for_each(|filtered_entity| {
let terms = filtered_entity
.components()
.map(|id| {
let ptr = filtered_entity.get_by_id(id).unwrap();
let info = component_info.get(&id).unwrap();
let len = info.layout().size() / std::mem::size_of::<u64>();
// SAFETY:
// - All components are created with layout [u64]
// - len is calculated from the component descriptor
let data = unsafe {
std::slice::from_raw_parts_mut(
ptr.assert_unique().as_ptr().cast::<u64>(),
len,
)
};
// If we have write access, increment each value once
if filtered_entity.access().has_component_write(id) {
data.iter_mut().for_each(|data| {
*data += 1;
});
}
format!("{}: {:?}", info.name(), data[0..len].to_vec())
})
.collect::<Vec<_>>()
.join(", ");
println!("{:?}: {}", filtered_entity.id(), terms);
});
}
_ => continue,
}
}
}
// Constructs `OwningPtr` for each item in `components`
// By sharing the lifetime of `components` with the resulting ptrs we ensure we don't drop the data before use
fn to_owning_ptrs(components: &mut [Vec<u64>]) -> Vec<OwningPtr<Aligned>> {
components
.iter_mut()
.map(|data| {
let ptr = data.as_mut_ptr();
// SAFETY:
// - Pointers are guaranteed to be non-null
// - Memory pointed to won't be dropped until `components` is dropped
unsafe {
let non_null = NonNull::new_unchecked(ptr.cast());
OwningPtr::new(non_null)
}
})
.collect()
}
fn parse_term<Q: QueryData>(
str: &str,
builder: &mut QueryBuilder<Q>,
components: &HashMap<String, ComponentId>,
) {
let mut matched = false;
let str = str.trim();
match str.chars().next() {
// Optional term
Some('?') => {
builder.optional(|b| parse_term(&str[1..], b, components));
matched = true;
}
// Reference term
Some('&') => {
let mut parts = str.split_whitespace();
let first = parts.next().unwrap();
if first == "&mut" {
if let Some(str) = parts.next() {
if let Some(&id) = components.get(str) {
builder.mut_id(id);
matched = true;
}
};
} else if let Some(&id) = components.get(&first[1..]) {
builder.ref_id(id);
matched = true;
}
}
// With term
Some(_) => {
if let Some(&id) = components.get(str) {
builder.with_id(id);
matched = true;
}
}
None => {}
};
if !matched {
println!("Unable to find component: {}", str);
}
}
fn parse_query<Q: QueryData>(
str: &str,
builder: &mut QueryBuilder<Q>,
components: &HashMap<String, ComponentId>,
) {
let str = str.split(',');
str.for_each(|term| {
let sub_terms: Vec<_> = term.split("||").collect();
if sub_terms.len() == 1 {
parse_term(sub_terms[0], builder, components);
} else {
builder.or(|b| {
sub_terms
.iter()
.for_each(|term| parse_term(term, b, components));
});
}
});
}