pub trait Index<Idx>where
Idx: ?Sized,{
type Output: ?Sized;
// Required method
fn index(&self, index: Idx) -> &Self::Output;
}Expand description
Used for indexing operations (container[index]) in immutable contexts.
container[index] is actually syntactic sugar for *container.index(index),
but only when used as an immutable value. If a mutable value is requested,
IndexMut is used instead. This allows nice things such as
let value = v[index] if the type of value implements Copy.
§Examples
The following example implements Index on a read-only NucleotideCount
container, enabling individual counts to be retrieved with index syntax.
use std::ops::Index;
enum Nucleotide {
A,
C,
G,
T,
}
struct NucleotideCount {
a: usize,
c: usize,
g: usize,
t: usize,
}
impl Index<Nucleotide> for NucleotideCount {
type Output = usize;
fn index(&self, nucleotide: Nucleotide) -> &Self::Output {
match nucleotide {
Nucleotide::A => &self.a,
Nucleotide::C => &self.c,
Nucleotide::G => &self.g,
Nucleotide::T => &self.t,
}
}
}
let nucleotide_count = NucleotideCount {a: 14, c: 9, g: 10, t: 12};
assert_eq!(nucleotide_count[Nucleotide::A], 14);
assert_eq!(nucleotide_count[Nucleotide::C], 9);
assert_eq!(nucleotide_count[Nucleotide::G], 10);
assert_eq!(nucleotide_count[Nucleotide::T], 12);Required Associated Types§
Required Methods§
Implementors§
Source§impl Index<Range<usize>> for UninitSlice
impl Index<Range<usize>> for UninitSlice
type Output = UninitSlice
Source§impl Index<RangeFrom<usize>> for UninitSlice
impl Index<RangeFrom<usize>> for UninitSlice
type Output = UninitSlice
Source§impl Index<RangeFull> for UninitSlice
impl Index<RangeFull> for UninitSlice
type Output = UninitSlice
Source§impl Index<RangeInclusive<usize>> for ByteString
impl Index<RangeInclusive<usize>> for ByteString
Source§impl Index<RangeInclusive<usize>> for UninitSlice
impl Index<RangeInclusive<usize>> for UninitSlice
type Output = UninitSlice
Source§impl Index<RangeTo<usize>> for UninitSlice
impl Index<RangeTo<usize>> for UninitSlice
type Output = UninitSlice
Source§impl Index<RangeToInclusive<usize>> for ByteString
impl Index<RangeToInclusive<usize>> for ByteString
Source§impl Index<RangeToInclusive<usize>> for UninitSlice
impl Index<RangeToInclusive<usize>> for UninitSlice
type Output = UninitSlice
Source§impl<'h> Index<usize> for regex::regex::bytes::Captures<'h>
Get a matching capture group’s haystack substring by index.
impl<'h> Index<usize> for regex::regex::bytes::Captures<'h>
Get a matching capture group’s haystack substring by index.
The haystack substring returned can’t outlive the Captures object if this
method is used, because of how Index is defined (normally a[i] is part
of a and can’t outlive it). To work around this limitation, do that, use
Captures::get instead.
'h is the lifetime of the matched haystack, but the lifetime of the
&str returned by this implementation is the lifetime of the Captures
value itself.
§Panics
If there is no matching group at the given index.
Source§impl<'h> Index<usize> for regex::regex::string::Captures<'h>
Get a matching capture group’s haystack substring by index.
impl<'h> Index<usize> for regex::regex::string::Captures<'h>
Get a matching capture group’s haystack substring by index.
The haystack substring returned can’t outlive the Captures object if this
method is used, because of how Index is defined (normally a[i] is part
of a and can’t outlive it). To work around this limitation, do that, use
Captures::get instead.
'h is the lifetime of the matched haystack, but the lifetime of the
&str returned by this implementation is the lifetime of the Captures
value itself.
§Panics
If there is no matching group at the given index.
Source§impl<'h, 'n> Index<&'n str> for regex::regex::bytes::Captures<'h>
Get a matching capture group’s haystack substring by name.
impl<'h, 'n> Index<&'n str> for regex::regex::bytes::Captures<'h>
Get a matching capture group’s haystack substring by name.
The haystack substring returned can’t outlive the Captures object if this
method is used, because of how Index is defined (normally a[i] is part
of a and can’t outlive it). To work around this limitation, do that, use
Captures::name instead.
'h is the lifetime of the matched haystack, but the lifetime of the
&str returned by this implementation is the lifetime of the Captures
value itself.
'n is the lifetime of the group name used to index the Captures value.
§Panics
If there is no matching group at the given name.
Source§impl<'h, 'n> Index<&'n str> for regex::regex::string::Captures<'h>
Get a matching capture group’s haystack substring by name.
impl<'h, 'n> Index<&'n str> for regex::regex::string::Captures<'h>
Get a matching capture group’s haystack substring by name.
The haystack substring returned can’t outlive the Captures object if this
method is used, because of how Index is defined (normally a[i] is part
of a and can’t outlive it). To work around this limitation, do that, use
Captures::name instead.
'h is the lifetime of the matched haystack, but the lifetime of the
&str returned by this implementation is the lifetime of the Captures
value itself.
'n is the lifetime of the group name used to index the Captures value.
§Panics
If there is no matching group at the given name.
Source§impl<Q> Index<&Q> for Map<String, Value>
Access an element of this map. Panics if the given key is not present in the
map.
impl<Q> Index<&Q> for Map<String, Value>
Access an element of this map. Panics if the given key is not present in the map.
match val {
Value::String(s) => Some(s.as_str()),
Value::Array(arr) => arr[0].as_str(),
Value::Object(map) => map["type"].as_str(),
_ => None,
}