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use crate::*;
/// Traverse a value's fields and variants.
///
/// Each method of the `Visit` trait is a hook that enables the implementor to
/// observe value fields. By default, most methods are implemented as a no-op.
/// The `visit_primitive_slice` default implementation will iterate the slice,
/// calling `visit_value` with each item.
///
/// To recurse, the implementor must implement methods to visit the arguments.
///
/// # Examples
///
/// Recursively printing a Rust value.
///
/// ```
/// use valuable::{NamedValues, Valuable, Value, Visit};
///
/// struct Print(String);
///
/// impl Print {
/// fn indent(&self) -> Print {
/// Print(format!("{} ", self.0))
/// }
/// }
///
/// impl Visit for Print {
/// fn visit_value(&mut self, value: Value<'_>) {
/// match value {
/// Value::Structable(v) => {
/// let def = v.definition();
/// // Print the struct name
/// println!("{}{}:", self.0, def.name());
///
/// // Visit fields
/// let mut visit = self.indent();
/// v.visit(&mut visit);
/// }
/// Value::Enumerable(v) => {
/// let def = v.definition();
/// let variant = v.variant();
/// // Print the enum name
/// println!("{}{}::{}:", self.0, def.name(), variant.name());
///
/// // Visit fields
/// let mut visit = self.indent();
/// v.visit(&mut visit);
/// }
/// Value::Listable(v) => {
/// println!("{}", self.0);
///
/// // Visit fields
/// let mut visit = self.indent();
/// v.visit(&mut visit);
/// }
/// Value::Mappable(v) => {
/// println!("{}", self.0);
///
/// // Visit fields
/// let mut visit = self.indent();
/// v.visit(&mut visit);
/// }
/// // Primitive or unknown type, just render Debug
/// v => println!("{:?}", v),
/// }
/// }
///
/// fn visit_named_fields(&mut self, named_values: &NamedValues<'_>) {
/// for (field, value) in named_values {
/// print!("{}- {}: ", self.0, field.name());
/// value.visit(self);
/// }
/// }
///
/// fn visit_unnamed_fields(&mut self, values: &[Value<'_>]) {
/// for value in values {
/// print!("{}- ", self.0);
/// value.visit(self);
/// }
/// }
///
/// fn visit_entry(&mut self, key: Value<'_>, value: Value<'_>) {
/// print!("{}- {:?}: ", self.0, key);
/// value.visit(self);
/// }
/// }
///
/// #[derive(Valuable)]
/// struct Person {
/// name: String,
/// age: u32,
/// addresses: Vec<Address>,
/// }
///
/// #[derive(Valuable)]
/// struct Address {
/// street: String,
/// city: String,
/// zip: String,
/// }
///
/// let person = Person {
/// name: "Angela Ashton".to_string(),
/// age: 31,
/// addresses: vec![
/// Address {
/// street: "123 1st Ave".to_string(),
/// city: "Townsville".to_string(),
/// zip: "12345".to_string(),
/// },
/// Address {
/// street: "555 Main St.".to_string(),
/// city: "New Old Town".to_string(),
/// zip: "55555".to_string(),
/// },
/// ],
/// };
///
/// let mut print = Print("".to_string());
/// valuable::visit(&person, &mut print);
/// ```
pub trait Visit {
/// Visit a single value.
///
/// The `visit_value` method is called once when visiting single primitive
/// values. When visiting `Listable` types, the `visit_value` method is
/// called once per item in the listable type.
///
/// Note, in the case of Listable types containing primitive types,
/// `visit_primitive_slice` can be implemented instead for less overhead.
///
/// # Examples
///
/// Visiting a single value.
///
/// ```
/// use valuable::{Valuable, Visit, Value};
///
/// struct Print;
///
/// impl Visit for Print {
/// fn visit_value(&mut self, value: Value<'_>) {
/// println!("{:?}", value);
/// }
/// }
///
/// let my_val = 123;
/// my_val.visit(&mut Print);
/// ```
///
/// Visiting multiple values in a list.
///
/// ```
/// use valuable::{Valuable, Value, Visit};
///
/// struct PrintList { comma: bool };
///
/// impl Visit for PrintList {
/// fn visit_value(&mut self, value: Value<'_>) {
/// match value {
/// Value::Listable(v) => v.visit(self),
/// value => {
/// if self.comma {
/// println!(", {:?}", value);
/// } else {
/// print!("{:?}", value);
/// self.comma = true;
/// }
/// }
/// }
/// }
/// }
///
/// let my_list = vec![1, 2, 3, 4, 5];
/// valuable::visit(&my_list, &mut PrintList { comma: false });
/// ```
fn visit_value(&mut self, value: Value<'_>);
/// Visit a struct or enum's named fields.
///
/// When the struct/enum is statically defined, all fields are known ahead
/// of time and `visit_named_fields` is called once with all field values.
/// When the struct/enum is dynamic, then the `visit_named_fields` method
/// may be called multiple times.
///
/// See [`Structable`] and [`Enumerable`] for static vs. dynamic details.
///
/// # Examples
///
/// Visiting all fields in a struct.
///
/// ```
/// use valuable::{NamedValues, Valuable, Value, Visit};
///
/// #[derive(Valuable)]
/// struct MyStruct {
/// hello: String,
/// world: u32,
/// }
///
/// struct Print;
///
/// impl Visit for Print {
/// fn visit_named_fields(&mut self, named_values: &NamedValues<'_>) {
/// for (field, value) in named_values {
/// println!("{:?}: {:?}", field, value);
/// }
/// }
///
/// fn visit_value(&mut self, value: Value<'_>) {
/// match value {
/// Value::Structable(v) => v.visit(self),
/// _ => {} // do nothing for other types
/// }
/// }
/// }
///
/// let my_struct = MyStruct {
/// hello: "Hello world".to_string(),
/// world: 42,
/// };
///
/// valuable::visit(&my_struct, &mut Print);
/// ```
fn visit_named_fields(&mut self, named_values: &NamedValues<'_>) {
let _ = named_values;
}
/// Visit a struct or enum's unnamed fields.
///
/// When the struct/enum is statically defined, all fields are known ahead
/// of time and `visit_unnamed_fields` is called once with all field values.
/// When the struct/enum is dynamic, then the `visit_unnamed_fields` method
/// may be called multiple times.
///
/// See [`Structable`] and [`Enumerable`] for static vs. dynamic details.
///
/// # Examples
///
/// Visiting all fields in a struct.
///
/// ```
/// use valuable::{Valuable, Value, Visit};
///
/// #[derive(Valuable)]
/// struct MyStruct(String, u32);
///
/// struct Print;
///
/// impl Visit for Print {
/// fn visit_unnamed_fields(&mut self, values: &[Value<'_>]) {
/// for value in values {
/// println!("{:?}", value);
/// }
/// }
///
/// fn visit_value(&mut self, value: Value<'_>) {
/// match value {
/// Value::Structable(v) => v.visit(self),
/// _ => {} // do nothing for other types
/// }
/// }
/// }
///
/// let my_struct = MyStruct("Hello world".to_string(), 42);
///
/// valuable::visit(&my_struct, &mut Print);
/// ```
fn visit_unnamed_fields(&mut self, values: &[Value<'_>]) {
let _ = values;
}
/// Visit a primitive slice.
///
/// This method exists as an optimization when visiting [`Listable`] types.
/// By default, `Listable` types are visited by passing each item to
/// `visit_value`. However, if the listable stores a **primitive** type
/// within contiguous memory, then `visit_primitive_slice` is called
/// instead.
///
/// When implementing `visit_primitive_slice`, be aware that the method may
/// be called multiple times for a single `Listable` type.
///
/// # Examples
///
/// A vec calls `visit_primitive_slice` one time, but a `VecDeque` will call
/// `visit_primitive_slice` twice.
///
/// ```
/// use valuable::{Valuable, Value, Visit, Slice};
/// use std::collections::VecDeque;
///
/// struct Count(u32);
///
/// impl Visit for Count {
/// fn visit_primitive_slice(&mut self, slice: Slice<'_>) {
/// self.0 += 1;
/// }
///
/// fn visit_value(&mut self, value: Value<'_>) {
/// match value {
/// Value::Listable(v) => v.visit(self),
/// _ => {} // do nothing for other types
/// }
/// }
/// }
///
/// let vec = vec![1, 2, 3, 4, 5];
///
/// let mut count = Count(0);
/// valuable::visit(&vec, &mut count);
/// assert_eq!(1, count.0);
///
/// let mut vec_deque = VecDeque::from(vec);
///
/// let mut count = Count(0);
/// valuable::visit(&vec_deque, &mut count);
///
/// assert_eq!(2, count.0);
/// ```
fn visit_primitive_slice(&mut self, slice: Slice<'_>) {
for value in slice {
self.visit_value(value);
}
}
/// Visit a `Mappable`'s entries.
///
/// The `visit_entry` method is called once for each entry contained by a
/// `Mappable.`
///
/// # Examples
///
/// Visit a map's entries
///
/// ```
/// use valuable::{Valuable, Value, Visit};
/// use std::collections::HashMap;
///
/// let mut map = HashMap::new();
/// map.insert("hello", 123);
/// map.insert("world", 456);
///
/// struct Print;
///
/// impl Visit for Print {
/// fn visit_entry(&mut self, key: Value<'_>, value: Value<'_>) {
/// println!("{:?} => {:?}", key, value);
/// }
///
/// fn visit_value(&mut self, value: Value<'_>) {
/// match value {
/// Value::Mappable(v) => v.visit(self),
/// _ => {} // do nothing for other types
/// }
/// }
/// }
///
/// valuable::visit(&map, &mut Print);
/// ```
fn visit_entry(&mut self, key: Value<'_>, value: Value<'_>) {
let _ = (key, value);
}
}
macro_rules! deref {
(
$(
$(#[$attrs:meta])*
$ty:ty,
)*
) => {
$(
$(#[$attrs])*
impl<T: ?Sized + Visit> Visit for $ty {
fn visit_value(&mut self, value: Value<'_>) {
T::visit_value(&mut **self, value)
}
fn visit_named_fields(&mut self, named_values: &NamedValues<'_>) {
T::visit_named_fields(&mut **self, named_values)
}
fn visit_unnamed_fields(&mut self, values: &[Value<'_>]) {
T::visit_unnamed_fields(&mut **self, values)
}
fn visit_primitive_slice(&mut self, slice: Slice<'_>) {
T::visit_primitive_slice(&mut **self, slice)
}
fn visit_entry(&mut self, key: Value<'_>, value: Value<'_>) {
T::visit_entry(&mut **self, key, value)
}
}
)*
};
}
deref! {
&mut T,
#[cfg(feature = "alloc")]
alloc::boxed::Box<T>,
}
/// Inspects a value by calling the relevant [`Visit`] methods with `value`'s
/// data.
///
/// This method calls [`Visit::visit_value()`] with the provided [`Valuable`]
/// instance. See [`Visit`] documentation for more details.
///
/// # Examples
///
/// Extract a single field from a struct. Note: if the same field is repeatedly
/// extracted from a struct, it is preferable to obtain the associated
/// [`NamedField`] once and use it repeatedly.
///
/// ```
/// use valuable::{NamedValues, Valuable, Value, Visit};
///
/// #[derive(Valuable)]
/// struct MyStruct {
/// foo: usize,
/// bar: usize,
/// }
///
/// struct GetFoo(usize);
///
/// impl Visit for GetFoo {
/// fn visit_named_fields(&mut self, named_values: &NamedValues<'_>) {
/// if let Some(foo) = named_values.get_by_name("foo") {
/// if let Some(val) = foo.as_usize() {
/// self.0 = val;
/// }
/// }
/// }
///
/// fn visit_value(&mut self, value: Value<'_>) {
/// if let Value::Structable(v) = value {
/// v.visit(self);
/// }
/// }
/// }
///
/// let my_struct = MyStruct {
/// foo: 123,
/// bar: 456,
/// };
///
/// let mut get_foo = GetFoo(0);
/// valuable::visit(&my_struct, &mut get_foo);
///
/// assert_eq!(123, get_foo.0);
/// ```
///
/// [`Visit`]: Visit [`NamedField`]: crate::NamedField
pub fn visit(value: &impl Valuable, visit: &mut dyn Visit) {
visit.visit_value(value.as_value());
}