Derive Macro builder 

#[derive(builder)]
{
    // Attributes available to this derive:
    #[new]
}

Generates appropriate builder methods for a struct.

This assumes that the struct itself acts like a builder.

This derive macro also adds a #[new] helper attribute. If this is added to the struct, a new function is also generated with a where Self: Default bound.

The builder methods generated for each field will have that field’s visibility: private fields will have private methods, etc.

Examples

#[derive(Default, builder)]
#[new]
struct Example {
    pub x: i32,
    pub y: i32,
}

This will derive the following implementations:

impl Example {
    /// Creates a new `Example`.
    ///
    /// This is equivalent to <code>Example::[default()]</code>.
    ///
    /// [default()]: Default::default()
    pub fn new() -> Self
    where
        Self: Default,
    {
        Self::default()
    }

    /// Sets `x` to the given value.
    pub fn x(mut self, x: i32) -> Self {
        self.x = x;

        self
    }

    /// Sets `y` to the given value.
    pub fn y(mut self, y: i32) -> Self {
        self.y = y;

        self
    }
}

#[derive(builder)] also works on tuple structs (with any number of fields):

#[derive(Default, builder)]
struct Example(pub i32, pub i32);

This will derive the following implementations:

impl Example {
    /// Sets the first field to the given value.
    pub fn first(mut self, first: i32) -> Self {
        self.0 = first;

        self
    }

    /// Sets the second field to the given value.
    pub fn second(mut self, second: i32) -> Self {
        self.1 = second;

        self
    }
}