Optbuilder

This crate was born out of my laziness while implementing a wrapper for the Telegram API. Many methods of the API required parameters that were mostly optional, leaving me in a situation where I would write code like this:

struct Foo {
    name: String,
    age: u32,
    address: Option<String>,
    job: Option<String>,
    pet_name: Option<String>
}

impl Foo {
    fn with_address(self, addr: String) -> self {
        self.address = Some(addr);
    }

    fn with_job(self, job: String) -> self {
        self.job = Some(job);
    }

    fn with_pet_name(self, pet_name: String) -> self {
        self.pet_name = Some(pet_name);
    }
}

instead of implementing all the methods to inject address, job and pet_name a macro was created for that purpose:

extern crate optbuilder;
use optbuilder::OptionalBuilder;

#[derive(OptionalBuilder)]
struct Foo {
    name: String,
    age: u32,
    address: Option<String>,
    // We don't want to codegen job for some reason
    #[optbuilder(skip)]
    job: Option<String>,
    pet_name: Option<String>
}

How to use this?

Add the following lines to your Cargo.toml

[dependencies]
optbuilder = "0.1.1"

Why not use a builder crate?

Basically because many times I had a default implementation that turned the option types to None

Issues

Since the From trait is used extensively on the crate, the compiler may complain about types and errors like this can happen

use optbuilder::OptionalBuilder;

#[derive(Debug, Default, OptionalBuilder)]
struct Foo {
    name: String,
    id: Option<i32>,
    uid: Option<u32>,
}

fn main() {
    let f = Foo::default().with_id(2).with_uid(3);

    println!("{:?}", f);
}

error[E0277]: the trait bound `u32: std::convert::From<i32>` is not satisfied
  --> src/main.rs:11:39
   |
11 |     let f = Foo::default().with_id(2).with_uid(3);
   |                                       ^^^^^^^^ the trait `std::convert::From<i32>` is not implemented for `u32`