Module kobold::branching

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Utilities for conditional rendering

The view! macro produces unique transient types, so you might run into compile errors when branching:

ⓘ
#[component]
fn Conditional(illuminatus: bool) -> impl View {
    if illuminatus {
        view! { <p>"It was the year when they finally immanentized the Eschaton."</p> }
    } else {
        view! { <blockquote>"It was love at first sight."</blockquote> }
    }
}

Here Rust will inform you that:

/     if illuminatus {
|         view! { <p>"It was the year when they finally immanentized the Eschaton."</p> }
|         ------------------------------------------------------------------------------- expected because of this
|     } else {
|         view! { <blockquote>"It was love at first sight."</blockquote> }
|         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected struct `Conditional::render::Transient`, found a different struct `Conditional::render::Transient`
|     }
|_____- `if` and `else` have incompatible types

While both types are named Transient, they are in fact different types defined inline by the macro.

In most cases all you have to do is annotate such component with #[component(auto_branch)]:

#[component(auto_branch)]
fn Conditional(illuminatus: bool) -> impl View {
    if illuminatus {
        view! { <p>"It was the year when they finally immanentized the Eschaton."</p> }
    } else {
        view! { <blockquote>"It was love at first sight."</blockquote> }
    }
}

This flag is not enabled by default, yet, as there might be situations auto_branch doesn’t handle correctly.

Manual branching

An always safe if more laborious way is to manually use one of the BranchN enums from this module:

use kobold::branching::Branch2;

#[component]
fn Conditional(illuminatus: bool) -> impl View {
    if illuminatus {
        Branch2::A(view! {
            <p>"It was the year when they finally immanentized the Eschaton."</p>
        })
    } else {
        Branch2::B(view! {
            <blockquote>"It was love at first sight."</blockquote>
        })
    }
}

This is in fact all that the auto_branch flag does for you automatically.

For simple optional renders you can always use the standard library Option:

#[component]
fn Conditional(illuminatus: bool) -> impl View {
    if illuminatus {
        Some(view! {
            <p>"It was the year when they finally immanentized the Eschaton."</p>
        })
    } else {
        None
    }
}

Structs

Enums