Derive Macro druid_derive::Data

#[derive(Data)]
{
    // Attributes available to this derive:
    #[data]
}

Generates implementations of the Data trait.

This macro supports a data field attribute with the following arguments:

• #[data(ignore)] makes the generated Data::same function skip comparing this field.
• #[data(same_fn="foo")] uses the function foo for comparing this field. foo should be the name of a function with signature fn(&T, &T) -> bool, where T is the type of the field.
• #[data(eq)] is shorthand for #[data(same_fn = "PartialEq::eq")]

Example

use druid_derive::Data;

#[derive(Clone, Data)]
struct State {
    number: f64,
    // `Vec` doesn't implement `Data`, so we need to either ignore it or supply a `same_fn`.
    #[data(eq)]
    // same as #[data(same_fn="PartialEq::eq")]
    indices: Vec<usize>,
    // This is just some sort of cache; it isn't important for sameness comparison.
    #[data(ignore)]
    cached_indices: Vec<usize>,
}