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 Commands 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?
102 fn event(
103 &mut self,
104 child: &mut Label<u64>,
105 ctx: &mut EventCtx,
106 event: &Event,
107 data: &mut u64,
108 env: &Env,
109 ) {
110 match event {
111 Event::Command(cmd) if cmd.is(INCREMENT) => *data += 1,
112 _ => child.event(ctx, event, data, env),
113 }
114 }More examples
151 fn command(
152 &mut self,
153 ctx: &mut DelegateCtx,
154 _target: Target,
155 cmd: &Command,
156 data: &mut State,
157 _env: &Env,
158 ) -> Handled {
159 if cmd.is(sys_cmds::NEW_FILE) {
160 let new_win = WindowDesc::new(ui_builder())
161 .menu(make_menu)
162 .window_size((data.selected as f64 * 100.0 + 300.0, 500.0));
163 ctx.new_window(new_win);
164 Handled::Yes
165 } else {
166 Handled::No
167 }
168 }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?
86 fn command(
87 &mut self,
88 _ctx: &mut DelegateCtx,
89 _target: Target,
90 cmd: &Command,
91 data: &mut AppState,
92 _env: &Env,
93 ) -> Handled {
94 if let Some(number) = cmd.get(FINISH_SLOW_FUNCTION) {
95 // If the command we received is `FINISH_SLOW_FUNCTION` handle the payload.
96 data.processing = false;
97 data.value = *number;
98 Handled::Yes
99 } else {
100 Handled::No
101 }
102 }More examples
75 fn command(
76 &mut self,
77 _ctx: &mut DelegateCtx,
78 _target: Target,
79 cmd: &Command,
80 _data: &mut T,
81 _env: &Env,
82 ) -> Handled {
83 if let Some(url) = cmd.get(OPEN_LINK) {
84 #[cfg(not(target_arch = "wasm32"))]
85 open::that_in_background(url);
86 #[cfg(target_arch = "wasm32")]
87 tracing::warn!("opening link({}) not supported on web yet.", url);
88 Handled::Yes
89 } else {
90 Handled::No
91 }
92 }77 fn command(
78 &mut self,
79 _ctx: &mut DelegateCtx,
80 _target: Target,
81 cmd: &Command,
82 data: &mut String,
83 _env: &Env,
84 ) -> Handled {
85 if let Some(file_info) = cmd.get(commands::SAVE_FILE_AS) {
86 if let Err(e) = std::fs::write(file_info.path(), &data[..]) {
87 println!("Error writing file: {e}");
88 }
89 return Handled::Yes;
90 }
91 if let Some(file_info) = cmd.get(commands::OPEN_FILE) {
92 match std::fs::read_to_string(file_info.path()) {
93 Ok(s) => {
94 let first_line = s.lines().next().unwrap_or("");
95 *data = first_line.to_owned();
96 }
97 Err(e) => {
98 println!("Error opening file: {e}");
99 }
100 }
101 return Handled::Yes;
102 }
103 Handled::No
104 }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.