Trait CallbackReturn 

pub trait CallbackReturn {
    type FoldType: Default;

    // Required method
    fn fold_callback_return(folded: Self::FoldType, ret: Self) -> Self::FoldType;

    // Provided method
    fn callback_fold_default() -> Self::FoldType { ... }
}

A type which can be returned from a callback and folded into a single value

As an example, here’s the provided implementation for bool:

/// Returns true if any of the callbacks returned true without short circuiting
impl CallbackReturn for bool {
    type FoldType = bool;
 
    fn fold_callback_return(folded: Self::FoldType, ret: Self) -> Self::FoldType {
        folded | ret
    }
}

The way this is used is by taking the FoldType and creating a default instance. For a bool this will be false. Then, for each callback return value it will take the previous instance (starting with false) and do previous | current_callback_return.

The result will mean that if callbacks a, b, and c are registered, the resulting value returned from <callback>::trigger(...) is ((false | a) | b) | c. (Parenthesis added to demonstrate folding order)

Required Associated Types

type FoldType: Default

Required Methods

fn fold_callback_return(folded: Self::FoldType, ret: Self) -> Self::FoldType

Function for folding each callback return value into a single value

Provided Methods

fn callback_fold_default() -> Self::FoldType

Get the default value for folding the callback returns into a single value

Dyn Compatibility

This trait is not dyn compatible.

In older versions of Rust, dyn compatibility was called "object safety", so this trait is not object safe.

Implementations on Foreign Types

impl CallbackReturn for bool

Returns true if any of the callbacks returned true without short circuiting

type FoldType = bool

fn fold_callback_return(folded: Self::FoldType, ret: Self) -> Self::FoldType

impl CallbackReturn for i8

Returns the first non-zero value without short-circuiting

type FoldType = i8

fn fold_callback_return(folded: Self::FoldType, ret: Self) -> Self::FoldType

impl CallbackReturn for i16

Returns the first non-zero value without short-circuiting

type FoldType = i16

fn fold_callback_return(folded: Self::FoldType, ret: Self) -> Self::FoldType

impl CallbackReturn for i32

Returns the first non-zero value without short-circuiting

type FoldType = i32

fn fold_callback_return(folded: Self::FoldType, ret: Self) -> Self::FoldType

impl CallbackReturn for i64

Returns the first non-zero value without short-circuiting

type FoldType = i64

fn fold_callback_return(folded: Self::FoldType, ret: Self) -> Self::FoldType

impl CallbackReturn for isize

Returns the first non-zero value without short-circuiting

type FoldType = isize

fn fold_callback_return(folded: Self::FoldType, ret: Self) -> Self::FoldType

impl CallbackReturn for u8

Returns the first non-zero value without short-circuiting

type FoldType = u8

fn fold_callback_return(folded: Self::FoldType, ret: Self) -> Self::FoldType

impl CallbackReturn for u16

Returns the first non-zero value without short-circuiting

type FoldType = u16

fn fold_callback_return(folded: Self::FoldType, ret: Self) -> Self::FoldType

impl CallbackReturn for u32

Returns the first non-zero value without short-circuiting

type FoldType = u32

fn fold_callback_return(folded: Self::FoldType, ret: Self) -> Self::FoldType

impl CallbackReturn for u64

Returns the first non-zero value without short-circuiting

type FoldType = u64

fn fold_callback_return(folded: Self::FoldType, ret: Self) -> Self::FoldType

impl CallbackReturn for usize

Returns the first non-zero value without short-circuiting

type FoldType = usize

fn fold_callback_return(folded: Self::FoldType, ret: Self) -> Self::FoldType

Implementors