Attribute Macro deltastruct 

#[deltastruct]

An attribute macro applied to mods. Will generate a Delta and it’s DeltaStruct<_> implementation.

Applied to a mod. Expects the mod to have a struct with the same name and an implementation. Currently at least one field is expected in the struct definition and at least one method is expected in the implementation. This macro will generate an enum with the same name as the mod with Delta appended, and an implementation impl DeltaStruct<FooDelta> for Foo.

The delta will have a tuple variant for each method defined for the struct converted to camel case, and it’s tuple will be of the same type as the argument list of it’s respective method (without &mut self). It will also expose delta functions of it’s fields.

Example:

#[deltastruct]
mod Foo {
  struct Foo {
    x : i32,
    y : i32
  }

  impl Foo {
    fn swap(&mut self) {
      let tmp = self.x;
      self.x = self.y;
      self.y = tmp;
    }
     
    fn do_stuff(&mut self, n : f64) {
      self.x = (n * (self.x as f64)) as i32;
    }
  }
}

will generate:

enum FooDelta {
  Swap(),
  DoStuff(f64),
  X(i32Delta),
  Y(i32Delta),
}

impl DeltaStruct<FooDelta> for Foo {
  fn apply(&mut self, delta : &FooDelta) {
    /* ... */
  }
}