Trait Pattern

pub trait Pattern: Sized {
    type Searcher<'a>: Searcher<'a>;

    // Required methods
    fn into_searcher(self, haystack: &str) -> Self::Searcher<'_>;
    fn as_utf8_pattern(&self) -> Option<Utf8Pattern<'_>>;

    // Provided methods
    fn is_contained_in(self, haystack: &str) -> bool { ... }
    fn is_prefix_of(self, haystack: &str) -> bool { ... }
    fn is_suffix_of<'a>(self, haystack: &'a str) -> bool
       where Self::Searcher<'a>: ReverseSearcher<'a> { ... }
    fn strip_prefix_of(self, haystack: &str) -> Option<&str> { ... }
    fn strip_suffix_of<'a>(self, haystack: &'a str) -> Option<&'a str>
       where Self::Searcher<'a>: ReverseSearcher<'a> { ... }
}

🔬This is a nightly-only experimental API. (pattern #27721)

A string pattern.

A Pattern expresses that the implementing type can be used as a string pattern for searching in a &str.

For example, both 'a' and "aa" are patterns that would match at index 1 in the string "baaaab".

The trait itself acts as a builder for an associated Searcher type, which does the actual work of finding occurrences of the pattern in a string.

Depending on the type of the pattern, the behaviour of methods like str::find and str::contains can change. The table below describes some of those behaviours.

Pattern type	Match condition
&str	is substring
char	is contained in string
&[char]	any char in slice is contained in string
F: FnMut(char) -> bool	F returns true for a char in string
&&str	is substring
&String	is substring

Examples

// &str
assert_eq!("abaaa".find("ba"), Some(1));
assert_eq!("abaaa".find("bac"), None);

// char
assert_eq!("abaaa".find('a'), Some(0));
assert_eq!("abaaa".find('b'), Some(1));
assert_eq!("abaaa".find('c'), None);

// &[char; N]
assert_eq!("ab".find(&['b', 'a']), Some(0));
assert_eq!("abaaa".find(&['a', 'z']), Some(0));
assert_eq!("abaaa".find(&['c', 'd']), None);

// &[char]
assert_eq!("ab".find(&['b', 'a'][..]), Some(0));
assert_eq!("abaaa".find(&['a', 'z'][..]), Some(0));
assert_eq!("abaaa".find(&['c', 'd'][..]), None);

// FnMut(char) -> bool
assert_eq!("abcdef_z".find(|ch| ch > 'd' && ch < 'y'), Some(4));
assert_eq!("abcddd_z".find(|ch| ch > 'd' && ch < 'y'), None);

Required Associated Types

type Searcher<'a>: Searcher<'a>

🔬This is a nightly-only experimental API. (pattern #27721)

Associated searcher for this pattern

Required Methods

fn into_searcher(self, haystack: &str) -> Self::Searcher<'_>

🔬This is a nightly-only experimental API. (pattern #27721)

Constructs the associated searcher from self and the haystack to search in.

fn as_utf8_pattern(&self) -> Option<Utf8Pattern<'_>>

🔬This is a nightly-only experimental API. (pattern #27721)

Returns the pattern as utf-8 bytes if possible.

Provided Methods

fn is_contained_in(self, haystack: &str) -> bool

🔬This is a nightly-only experimental API. (pattern #27721)

Checks whether the pattern matches anywhere in the haystack

fn is_prefix_of(self, haystack: &str) -> bool

🔬This is a nightly-only experimental API. (pattern #27721)

Checks whether the pattern matches at the front of the haystack

fn is_suffix_of<'a>(self, haystack: &'a str) -> bool

where Self::Searcher<'a>: ReverseSearcher<'a>,

🔬This is a nightly-only experimental API. (pattern #27721)

Checks whether the pattern matches at the back of the haystack

fn strip_prefix_of(self, haystack: &str) -> Option<&str>

🔬This is a nightly-only experimental API. (pattern #27721)

Removes the pattern from the front of haystack, if it matches.

fn strip_suffix_of<'a>(self, haystack: &'a str) -> Option<&'a str>

where Self::Searcher<'a>: ReverseSearcher<'a>,

🔬This is a nightly-only experimental API. (pattern #27721)

Removes the pattern from the back of haystack, if it matches.

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.

Implementors

impl Pattern for char

Searches for chars that are equal to a given char.

Examples

assert_eq!("Hello world".find('o'), Some(4));

type Searcher<'a> = CharSearcher<'a>

impl<'b> Pattern for &'b str

Non-allocating substring search.

Will handle the pattern "" as returning empty matches at each character boundary.

Examples

assert_eq!("Hello world".find("world"), Some(6));

type Searcher<'a> = StrSearcher<'a, 'b>

impl<'b> Pattern for &'b [char]

Searches for chars that are equal to any of the chars in the slice.

Examples

assert_eq!("Hello world".find(&['l', 'l'] as &[_]), Some(2));
assert_eq!("Hello world".find(&['l', 'l'][..]), Some(2));

type Searcher<'a> = CharSliceSearcher<'a, 'b>

impl<'b, 'c> Pattern for &'c &'b str

Delegates to the &str impl.

type Searcher<'a> = StrSearcher<'a, 'b>

impl<'b, const N: usize> Pattern for &'b [char; N]

Searches for chars that are equal to any of the chars in the array.

Examples

assert_eq!("Hello world".find(&['o', 'l']), Some(2));
assert_eq!("Hello world".find(&['h', 'w']), Some(6));

type Searcher<'a> = CharArrayRefSearcher<'a, 'b, N>

impl<F> Pattern for F

where F: FnMut(char) -> bool,

Searches for chars that match the given predicate.

Examples

assert_eq!("Hello world".find(char::is_uppercase), Some(0));
assert_eq!("Hello world".find(|c| "aeiou".contains(c)), Some(1));

type Searcher<'a> = CharPredicateSearcher<'a, F>

impl<const N: usize> Pattern for [char; N]

Searches for chars that are equal to any of the chars in the array.

Examples

assert_eq!("Hello world".find(['o', 'l']), Some(2));
assert_eq!("Hello world".find(['h', 'w']), Some(6));

type Searcher<'a> = CharArraySearcher<'a, N>