I try to implement a sort of zoom UI. The UI components are organized in
a tree. To update a component in the UI I use a search function
(match_fn() in the example) which take a closure as search criteria and
if it returns something I use an update function (test_mutable) with a
closure to do the update part. The update part only need an Id and the
closure. So returning the found component is not mandatory. If the
search function return only a copy of the component id it solves the
borrow error but I would like to have the found component.
I return a reference (Option<&'a Inside>) to avoid object copy. A
component can have a large sub tree. If I change and return a copy in
the search function (Option<Inside>) It works. Logic the Inside life
time start at the Some level (as I understand).
Perhaps you'll have a better idea to do this. I use this pattern (search
and update function) for this reasons:
* no multiple owned objects. All object are only owned in the tree.
* maintain most immutability
I put a new version of the test code nearer to my main code.
use std::vec::Vec;
use std::task;
pub enum UINode {
DrawableNode(Container),
ContainerNode(Inside),
}
struct Inside {
layout: fn(&Inside) -> uint,
}
impl Inside {
fn get_id(&self) -> uint {1}
}
trait Trait {}
struct ListInside {
tt: ~Trait: Send,
list: Vec<~UINode>,
}
struct Container {
inside:~ListInside,
}
impl ListInside {
fn match_fn<'a>(&'a self, filter: &'a |&'a UINode| -> Option<&'a
Inside>) ->Option<&'a Inside> {
for inside in self.list.iter() {
match (*filter)(*inside) {
Some(found) => return Some(found),
None => {},
};
}
None
}
fn test_mutable<'a>(&'a mut self, id: uint, update: &'a|component:
&'a mut Inside|) {}
}
fn TestMatchBorrow() {
let task = task::task();
task.spawn (proc() {
let mut viewList: Vec<~Container> = Vec::new();
for ref mut container in viewList.mut_iter() {
//let &mut my_var = &mut *(container.inside);
match container.inside.match_fn(&|inside: &UINode| ->
Option<&Inside> {None}) {
Some(inside) =>
container.inside.test_mutable(inside.get_id(), &|component: &mut Inside|
{}),
None => {},
}
}
});
}
#[main]
fn main() {
TestMatchBorrow();
}
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