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Override/add methods

In this page, we show how to do these in the example below:

  • Change the function signature / method implementation / ... of something in a third-party crate
  • Add arbitrary methods to existing structs/enums in third party crates

(Optional) How it is done​

How is the example below implemented? Shortly speaking, the #[ext] macro (which implements the "extension trait pattern") automatically generates a trait and an implementation, which flutter_rust_bridge picks up. Then, the frb_override_ prefix is recognized to automatically rename and override the original function.

Example​

Override existing methods​

Suppose the third party crate has code like:

pub struct S { ... }
impl S {
    pub fn greet(&self, name: &str) { ... }
}

Then we can override the greet function like:

use extend::ext; // or, for example, easy_ext's
use the_external_crate::path::to::S;

#[ext]
pub impl S {
    pub fn frb_override_greet(&self, age: i32, first_name: String, last_name: Vec<u8>) {
        // We can have arbitrary implementation.
        // Here, we demonstrate how to call the original implementation with modified arguments.
        self.greet(format!("{age}-{first_name}-{last_name:?}"))
    }
}

Add new methods​

It is very similar to the approach above, except that we do not need to prefix with frb_override_.