pub struct Command { /* private fields */ }
Expand description
An arbitrary command.
A Command
consists of a Selector
, that indicates what the command is
and what type of payload it carries, as well as the actual payload.
If the payload can’t or shouldn’t be cloned,
wrapping it with SingleUse
allows you to take
the payload.
The SingleUse
docs give an example on how to do this.
Generic payloads can be achieved with Selector<Box<dyn Any>>
.
In this case it could make sense to use utility functions to construct
such commands in order to maintain as much static typing as possible.
The EventCtx::new_window
method is an example of this.
Examples
use druid::{Command, Selector, Target};
let selector = Selector::new("process_rows");
let rows = vec![1, 3, 10, 12];
let command = selector.with(rows);
assert_eq!(command.get(selector), Some(&vec![1, 3, 10, 12]));
Implementations§
source§impl Command
impl Command
sourcepub fn new<T: Any>(
selector: Selector<T>,
payload: T,
target: impl Into<Target>
) -> Self
pub fn new<T: Any>( selector: Selector<T>, payload: T, target: impl Into<Target> ) -> Self
Create a new Command
with a payload and a Target
.
Selector::with
should be used to create Command
s more conveniently.
If you do not need a payload, Selector
implements Into<Command>
.
sourcepub fn to(self, target: impl Into<Target>) -> Self
pub fn to(self, target: impl Into<Target>) -> Self
Set the Command
’s Target
.
Command::target
can be used to get the current Target
.
sourcepub fn target(&self) -> Target
pub fn target(&self) -> Target
Returns the Command
’s Target
.
Command::to
can be used to change the Target
.
sourcepub fn is<T>(&self, selector: Selector<T>) -> bool
pub fn is<T>(&self, selector: Selector<T>) -> bool
Returns true
if self
matches this selector
.
Examples found in repository?
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fn event(
&mut self,
child: &mut Label<u64>,
ctx: &mut EventCtx,
event: &Event,
data: &mut u64,
env: &Env,
) {
match event {
Event::Command(cmd) if cmd.is(INCREMENT) => *data += 1,
_ => child.event(ctx, event, data, env),
}
}
More examples
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fn command(
&mut self,
ctx: &mut DelegateCtx,
_target: Target,
cmd: &Command,
data: &mut State,
_env: &Env,
) -> Handled {
if cmd.is(sys_cmds::NEW_FILE) {
let new_win = WindowDesc::new(ui_builder())
.menu(make_menu)
.window_size((data.selected as f64 * 100.0 + 300.0, 500.0));
ctx.new_window(new_win);
Handled::Yes
} else {
Handled::No
}
}
sourcepub fn get<T: Any>(&self, selector: Selector<T>) -> Option<&T>
pub fn get<T: Any>(&self, selector: Selector<T>) -> Option<&T>
Returns Some(&T)
(this Command
’s payload) if the selector matches.
Returns None
when self.is(selector) == false
.
Alternatively you can check the selector with is
and then use get_unchecked
.
Panics
Panics when the payload has a different type, than what the selector is supposed to carry. This can happen when two selectors with different types but the same key are used.
Examples found in repository?
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fn command(
&mut self,
_ctx: &mut DelegateCtx,
_target: Target,
cmd: &Command,
data: &mut AppState,
_env: &Env,
) -> Handled {
if let Some(number) = cmd.get(FINISH_SLOW_FUNCTION) {
// If the command we received is `FINISH_SLOW_FUNCTION` handle the payload.
data.processing = false;
data.value = *number;
Handled::Yes
} else {
Handled::No
}
}
More examples
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fn command(
&mut self,
_ctx: &mut DelegateCtx,
_target: Target,
cmd: &Command,
_data: &mut T,
_env: &Env,
) -> Handled {
if let Some(url) = cmd.get(OPEN_LINK) {
#[cfg(not(target_arch = "wasm32"))]
open::that_in_background(url);
#[cfg(target_arch = "wasm32")]
tracing::warn!("opening link({}) not supported on web yet.", url);
Handled::Yes
} else {
Handled::No
}
}
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fn command(
&mut self,
_ctx: &mut DelegateCtx,
_target: Target,
cmd: &Command,
data: &mut String,
_env: &Env,
) -> Handled {
if let Some(file_info) = cmd.get(commands::SAVE_FILE_AS) {
if let Err(e) = std::fs::write(file_info.path(), &data[..]) {
println!("Error writing file: {e}");
}
return Handled::Yes;
}
if let Some(file_info) = cmd.get(commands::OPEN_FILE) {
match std::fs::read_to_string(file_info.path()) {
Ok(s) => {
let first_line = s.lines().next().unwrap_or("");
*data = first_line.to_owned();
}
Err(e) => {
println!("Error opening file: {e}");
}
}
return Handled::Yes;
}
Handled::No
}
sourcepub fn get_unchecked<T: Any>(&self, selector: Selector<T>) -> &T
pub fn get_unchecked<T: Any>(&self, selector: Selector<T>) -> &T
Returns a reference to this Command
’s payload.
If the selector has already been checked with is
, then get_unchecked
can be used safely.
Otherwise you should use get
instead.
Panics
Panics when self.is(selector) == false
.
Panics when the payload has a different type, than what the selector is supposed to carry. This can happen when two selectors with different types but the same key are used.