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use super::{Disposable, Signal0, Signal1};
/// Represents a value that isn't ready yet, but may become available in the future.
pub struct Promise<A> {
/// Whether the result is available yet.
pub has_result: bool,
/// Emitted when the promise is fulfilled and the result has become available.
pub success: Signal1<A>,
/// An error message emitted if there was a problem during loading.
pub error: Signal1<String>,
/// May be emitted during loading when the progress or total counts have been updated.
pub progress_changed: Signal0,
/// The end result fulfilled by the promise. When accessing, throws an error if the result is not
/// yet available. Read hasResult to check availability first, or use get(). When setting, throws
/// an error if the result was already previously assigned.
pub result: Option<A>,
/// Context on how close this promise is to being fulfilled. For file IO, these are in bytes.
pub progress: f32,
pub total: f32,
}
impl<A> Promise<A> {
pub fn new() -> Self {
Self {
success: Signal1::new(None),
error: Signal1::new(None),
progress_changed: Signal0::new(None),
has_result: false,
progress: 0.0,
total: 0.0,
result: None,
}
}
pub fn result(&self) -> &Option<A> {
if !self.has_result {
panic!("Promise result not yet available");
}
&self.result
}
pub fn set_result(&self, result: Option<A>) -> Option<A> {
todo!("should deal with it");
// if self.hasResult {
// panic!("Promise result already assigned");
// }
// self.result = result;
// self.hasResult = true;
// self.success.emit(result);
// result
}
/// Passes the result to the callback now if the result is available, otherwise calls it later.
/// @returns If the callback was not called yet, a handle that can be disposed to cancel the
/// request.
pub fn get(&self, function: Box<dyn Fn(&A) + 'static>) -> Option<impl Disposable> {
if self.has_result {
if let Some(ref result) = self.result {
function(result);
}
return None;
}
let conn = self.success.connect(function, false).once().clone();
Some(conn)
}
#[inline]
pub fn progress(&self) -> f32 {
self.progress
}
pub fn set_progress(&mut self, progress: f32) {
if self.progress != progress {
self.progress = progress;
self.progress_changed.emit();
}
}
pub fn set_total(&mut self, total: f32) {
if self.total != total {
self.total = total;
self.progress_changed.emit();
}
}
#[inline]
pub fn total(&self) -> f32 {
self.total
}
}