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Override attributes

If the implementations of an external component (function/method/struct/enum/etc) is good, and we only want to add some attributes to it, then we only need to write down component name and new attributes inside our first-party package like below.

The rule is that:

  • Put the code inside src/third_party/{third-party-crate-name}/{path-to-the-module}.
  • Only write down function name, and no need to specify function arguments and return types.

Examples​

Example 1: Struct methods​

Suppose we are interested in the some_crate::hello::world::SomeStruct::method method in third-party crate:

// This is code in third-party crate, we cannot modify it
pub struct SomeStruct {
    ...
}

impl SomeStruct {
    pub fn method(&self, a: String, b: Vec<i32>) -> f32 {
        ...
    }
}

Then, we can write down the following lines to make that method has synchronous Dart code:

// src/third_party/some_crate/hello/world/mod.rs
#[frb(external)]
impl SomeStruct {
    #[frb(sync)] // <-- This attribute will be auto merged to third-party code
    pub fn method() {}
}

Example 2: Trait definition methods​

Support SomeTrait is a third party trait, then again we can do something like above.

#[frb(external)]
impl SomeTrait {
    #[frb(sync)]
    pub fn method() {}
}

Example 3: Trait implementation methods​

Suppose we have third party SomeTrait and SomeStruct implementing it. Then, to override the implementation method, we can do:

#[frb(external)]
impl MyTrait for MyStruct {
    #[frb(ignore)]
    fn method(a: i32, b: String) -> Vec<f64> {}
}

Note that, currently, we have to specify the function parameters (but still no need to have a body). This syntax may be simplified (i.e. no need to specify) in the future, and may not follow semantics versioning.

Remark on pub use​

flutter_rust_bridge understands syntax like pub use something::* and pub use another::Thing. Therefore, if a struct in third party code is defined non-publicly but then re-exported as public using such pub use grammar, flutter_rust_bridge will consider that type to be in the latter module.