mirror of https://github.com/LemmyNet/lemmy
WithoutId
dullbananas
10 months ago
committed by
GitHub
parent
86a433b0b3
commit
5e86922b0f
@ -0,0 +1,63 @@
|
||||
/// `macro_rules_attribute::derive(WithoutId!)` generates a variant of the struct with
|
||||
/// `WithoutId` added to the name and no `id` field.
|
||||
///
|
||||
/// This is useful for making less redundant selections of multiple joined tables.
|
||||
/// For example, selecting both `comment::post_id` and `post::id` is redundant if they
|
||||
/// have the same value. In this case, the selection of `post::id` can be avoided by selecting
|
||||
/// `PostWithoutId::as_select()` instead of `post::all_columns`.
|
||||
///
|
||||
/// This macro generates an `into_full` method, which converts to the sturct with `id`.
|
||||
/// For example, `PostWithoutId` would have this:
|
||||
///
|
||||
/// `pub fn into_full(self, id: PostId) -> Post`
|
||||
///
|
||||
/// The `id` value can come from a column in another table, like `comment::post_id`.
|
||||
///
|
||||
/// The generated struct implements `Selectable` and `Queryable`.
|
||||
macro_rules! WithoutId {
|
||||
(
|
||||
#[diesel(table_name = $table_name:ident)]
|
||||
$(#[$_struct_meta:meta])*
|
||||
$vis:vis struct $struct_name:ident {
|
||||
$(#[$_id_meta:meta])*
|
||||
$_id_vis:vis id: $id_type:ty,
|
||||
$(
|
||||
$(#[$_field_meta:meta])*
|
||||
$field_vis:vis $field_name:ident : $field_type:ty,
|
||||
)*
|
||||
}
|
||||
) => {
|
||||
::paste::paste! {
|
||||
#[derive(::diesel::Queryable, ::diesel::Selectable)]
|
||||
#[diesel(table_name = $table_name)]
|
||||
$vis struct [<$struct_name WithoutId>] {
|
||||
$(
|
||||
// Field attributes are not kept because either they are for other
|
||||
// derive macros, or they are `#[cfg(...)]` which is evaluated before
|
||||
// macro expansion.
|
||||
$field_vis $field_name : $field_type,
|
||||
)*
|
||||
}
|
||||
|
||||
impl [<$struct_name WithoutId>] {
|
||||
pub fn into_full(self, id: $id_type) -> $struct_name {
|
||||
$struct_name {
|
||||
$($field_name : self.$field_name,)*
|
||||
id,
|
||||
}
|
||||
}
|
||||
}
|
||||
}
|
||||
};
|
||||
|
||||
// Keep on removing the first attribute until `diesel(table_name = ...)` becomes
|
||||
// the first, which will cause the first pattern to be matched.
|
||||
(#[$_meta:meta] $($remaining:tt)*) => {
|
||||
$($remaining)*
|
||||
};
|
||||
|
||||
// This pattern is matched when there's no attributes.
|
||||
($_vis:vis struct $($_tt:tt)*) => {
|
||||
::std::compile_error!("`#[diesel(table_name = ...)]` is missing");
|
||||
};
|
||||
}
|
||||
Loading…
Reference in New Issue