Struct zng::event::CommandMeta

pub struct CommandMeta<'a> { /* private fields */ }

Access to metadata of a command.

The metadata storage can be accessed using the Command::with_meta method, implementers must declare and extension trait that adds methods that return CommandMetaVar or ReadOnlyCommandMetaVar that are stored in the CommandMeta. An initialization builder method for each value also must be provided to integrate with the command! macro.

Examples

The command! initialization transforms foo: true, to command.init_foo(true);, to support that, the command extension trait must have a foo and init_foo methods.

use zng_app::{event::*, var::*, static_id};

static_id! {
    static ref COMMAND_FOO_ID: CommandMetaVarId<bool>;
    static ref COMMAND_BAR_ID: CommandMetaVarId<bool>;
}

/// FooBar command values.
pub trait CommandFooBarExt {
    /// Gets read/write *foo*.
    fn foo(self) -> CommandMetaVar<bool>;

    /// Gets read-only *bar*.
    fn bar(self) -> ReadOnlyCommandMetaVar<bool>;

    /// Gets a read-only var derived from other metadata.
    fn foo_and_bar(self) -> BoxedVar<bool>;

    /// Init *foo*.
    fn init_foo(self, foo: bool) -> Self;

    /// Init *bar*.
    fn init_bar(self, bar: bool) -> Self;
}

impl CommandFooBarExt for Command {
    fn foo(self) -> CommandMetaVar<bool> {
        self.with_meta(|m| m.get_var_or_default(*COMMAND_FOO_ID))
    }

    fn bar(self) -> ReadOnlyCommandMetaVar<bool> {
        self.with_meta(|m| m.get_var_or_insert(*COMMAND_BAR_ID, ||true)).read_only()
    }

    fn foo_and_bar(self) -> BoxedVar<bool> {
        merge_var!(self.foo(), self.bar(), |f, b| *f && *b).boxed()
    }

    fn init_foo(self, foo: bool) -> Self {
        self.with_meta(|m| m.init_var(*COMMAND_FOO_ID, foo));
        self
    }

    fn init_bar(self, bar: bool) -> Self {
        self.with_meta(|m| m.init_var(*COMMAND_BAR_ID, bar));
        self
    }
}

Implementations

impl<'a> CommandMeta<'a>

pub fn get_or_insert<T, F>(&mut self, id: impl Into<StateId<T>>, init: F) -> T

where T: StateValue + Clone, F: FnOnce() -> T,

Clone a meta value identified by a StateId.

If the key is not set in the app, insert it using init to produce a value.

pub fn get_or_default<T>(&mut self, id: impl Into<StateId<T>>) -> T

where T: StateValue + Clone + Default,

Clone a meta value identified by a StateId.

If the key is not set, insert the default value and returns a clone of it.

pub fn get<T>(&self, id: impl Into<StateId<T>>) -> Option<T>

where T: StateValue + Clone,

Clone a meta value identified by a StateId if it is set.

pub fn set<T>(&mut self, id: impl Into<StateId<T>>, value: impl Into<T>)

where T: StateValue + Clone,

Set the meta value associated with the StateId.

pub fn init<T>(&mut self, id: impl Into<StateId<T>>, value: impl Into<T>)

where T: StateValue + Clone,

Set the metadata value only if it is not set.

This does not set the scoped override, only the command type metadata.

pub fn get_var_or_insert<T, F>( &mut self, id: impl Into<CommandMetaVarId<T>>, init: F, ) -> Box<dyn VarBoxed<T>>

where T: StateValue + VarValue, F: FnOnce() -> T,

Clone a meta variable identified by a CommandMetaVarId.

The variable is read-write and is clone-on-write if the command is scoped.

pub fn get_var<T>( &self, id: impl Into<CommandMetaVarId<T>>, ) -> Option<Box<dyn VarBoxed<T>>>

where T: StateValue + VarValue,

Clone a meta variable identified by a CommandMetaVarId, if it is set.

pub fn get_var_or_default<T>( &mut self, id: impl Into<CommandMetaVarId<T>>, ) -> Box<dyn VarBoxed<T>>

where T: StateValue + VarValue + Default,

Clone a meta variable identified by a CommandMetaVarId.

Inserts a variable with the default value if no variable is in the metadata.

pub fn init_var<T>( &mut self, id: impl Into<CommandMetaVarId<T>>, value: impl Into<T>, )

where T: StateValue + VarValue,

Set the metadata variable if it was not set.

This does not set the scoped override, only the command type metadata.