NSRegularExpression

An immutable representation of a compiled regular expression that you apply to Unicode strings.

Declaration

```

class NSRegularExpression:NSObject

```

Discussion

The fundamental matching method for NSRegularExpression is a Block iterator method that allows clients to supply a Block object which will be invoked each time the regular expression matches a portion of the target string. There are additional convenience methods for returning all the matches as an array, the total number of matches, the first match, and the range of the first match.

An individual match is represented by an instance of the NSTextCheckingResult class, which carries information about the overall matched range (via its range property), and the range of each individual capture group (via the range(at:) method). For basic NSRegularExpression objects, these match results will be of type regularExpression, but subclasses may use other types.

The ICU regular expressions supported by NSRegularExpression are described at http://userguide.icu-project.org/strings/regexp.

Examples Using NSRegularExpression

What follows are a set of graduated examples for using the NSRegularExpression class. All these examples use the regular expression \\b(a|b)(c|d)\\b as their regular expression.

This snippet creates a regular expression to match two-letter words, in which the first letter is “a” or “b” and the second letter is “c” or “d”. Specifying caseInsensitive means that matches will be case-insensitive, so this will match “BC”, “aD”, and so forth, as well as their lower-case equivalents.

NSError *error =NULL;NSRegularExpression *regex = [NSRegularExpression regularExpressionWithPattern:@"\\b(a|b)(c|d)\\b"options:NSRegularExpressionCaseInsensitive error:&error];

The numberOfMatches(in:options:range:) method provides a simple mechanism for counting the number of matches in a given range of a string.

NSUInteger numberOfMatches = [regex numberOfMatchesInString:string options:0range:NSMakeRange(0, [string length])];

If you are interested only in the overall range of the first match, the rangeOfFirstMatch(in:options:range:) method provides it for you. Some regular expressions (though not the example pattern) can successfully match a zero-length range, so the comparison of the resulting range with {NSNotFound, 0} is the most reliable way to determine whether there was a match or not.

The example regular expression contains two capture groups, corresponding to the two sets of parentheses, one for the first letter, and one for the second. If you are interested in more than just the overall matched range, you want to obtain an NSTextCheckingResult object corresponding to a given match. This object provides information about the overall matched range, via its range property, and also supplies the capture group ranges, via the range(at:)method. The first capture group range is given by [result rangeAtIndex:1], the second by [result rangeAtIndex:2]. Sending a result the range(at:) message and passing 0 is equivalent to [result range].

If the result returned is non-nil, then [result range] will always be a valid range, so it is not necessary to compare it against {NSNotFound, 0}. However, for some regular expressions (though not the example pattern) some capture groups may or may not participate in a given match. If a given capture group does not participate in a given match, then [result rangeAtIndex:idx] will return {NSNotFound, 0}.

NSRange rangeOfFirstMatch = [regex rangeOfFirstMatchInString:string options:0range:NSMakeRange(0, [string length])];if(!NSEqualRanges(rangeOfFirstMatch,NSMakeRange(NSNotFound,0))) { NSString *substringForFirstMatch = [string substringWithRange:rangeOfFirstMatch];}

The matches(in:options:range:) returns all the matching results.

NSArray *matches = [regex matchesInString:string options:0range:NSMakeRange(0, [string length])];for(NSTextCheckingResult *matchinmatches) { NSRange matchRange = [match range]; NSRange firstHalfRange = [match rangeAtIndex:1]; NSRange secondHalfRange = [match rangeAtIndex:2];}

The firstMatch(in:options:range:) method is similar to matches(in:options:range:) but it returns only the first match.

NSTextCheckingResult *match = [regex firstMatchInString:string options:0range:NSMakeRange(0, [string length])];if(match) { NSRange matchRange = [match range]; NSRange firstHalfRange = [match rangeAtIndex:1]; NSRange secondHalfRange = [match rangeAtIndex:2]; }

The Block enumeration method enumerateMatches(in:options:range:using:) is the most general and flexible of the matching methods of NSRegularExpression. It allows you to iterate through matches in a string, performing arbitrary actions on each as specified by the code in the Block and to stop partway through if desired. In the following example case, the iteration is stopped after a certain number of matches have been found.

If neither of the special options reportProgress or reportCompletion is specified, then the result argument to the Block is guaranteed to be non-nil, and as mentioned before, it is guaranteed to have a valid overall range. See NSRegularExpression.MatchingOptions for the significance of reportProgress or reportCompletion.

__block NSUInteger count =0;[regex enumerateMatchesInString:string options:0range:NSMakeRange(0, [string length]) usingBlock:^(NSTextCheckingResult *match, NSMatchingFlags flags, BOOL *stop){ NSRange matchRange = [match range]; NSRange firstHalfRange = [match rangeAtIndex:1]; NSRange secondHalfRange = [match rangeAtIndex:2];if(++count >=100) *stop = YES;}];

NSRegularExpression also provides simple methods for performing find-and-replace operations on a string. The following example returns a modified copy, but there is a corresponding method for modifying a mutable string in place. The template specifies what is to be used to replace each match, with $0 representing the contents of the overall matched range, $1 representing the contents of the first capture group, and so on. In this case, the template reverses the two letters of the word.

NSString *modifiedString = [regex stringByReplacingMatchesInString:string options:0range:NSMakeRange(0, [string length]) withTemplate:@"$2$1"];

Concurrency and Thread Safety

NSRegularExpression is designed to be immutable and thread safe, so that a single instance can be used in matching operations on multiple threads at once. However, the string on which it is operating should not be mutated during the course of a matching operation, whether from another thread or from within the Block used in the iteration.

Regular Expression Syntax

The following tables describe the character expressions used by the regular expression to match patterns within a string, the pattern operators that specify how many times a pattern is matched and additional matching restrictions, and the last table specifies flags that can be included in the regular expression pattern that specify search behavior over multiple lines (these flags can also be specified using the NSRegularExpression.Options option flags.

Regular Expression Metacharacters

Table 1 describe the character sequences used to match characters within a string.

Table 1

Regular Expression Metacharacters

Character ExpressionDescription

\aMatch a BELL, \u0007

\AMatch at the beginning of the input. Differs from ^ in that \A will not match after a new line within the input.

\b, outside of a [Set]Match if the current position is a word boundary. Boundaries occur at the transitions between word (\w) and non-word (\W) characters, with combining marks ignored. For better word boundaries, see useUnicodeWordBoundaries.

\b, within a [Set]Match a BACKSPACE, \u0008.

\BMatch if the current position is not a word boundary.

\cXMatch a control-X character

\dMatch any character with the Unicode General Category of Nd (Number, Decimal Digit.)

\DMatch any character that is not a decimal digit.

\eMatch an ESCAPE, \u001B.

\ETerminates a \Q ... \E quoted sequence.

\fMatch a FORM FEED, \u000C.

\GMatch if the current position is at the end of the previous match.

\nMatch a LINE FEED, \u000A.

\N{UNICODE CHARACTER NAME}Match the named character.

\p{UNICODE PROPERTY NAME}Match any character with the specified Unicode Property.

\P{UNICODE PROPERTY NAME}Match any character not having the specified Unicode Property.

\QQuotes all following characters until \E.

\rMatch a CARRIAGE RETURN, \u000D.

\sMatch a white space character. White space is defined as [\t\n\f\r\p{Z}].

\SMatch a non-white space character.

\tMatch a HORIZONTAL TABULATION, \u0009.

\uhhhhMatch the character with the hex value hhhh.

\UhhhhhhhhMatch the character with the hex value hhhhhhhh. Exactly eight hex digits must be provided, even though the largest Unicode code point is \U0010ffff.

\wMatch a word character. Word characters are [\p{Ll}\p{Lu}\p{Lt}\p{Lo}\p{Nd}].

\WMatch a non-word character.

\x{hhhh}Match the character with hex value hhhh. From one to six hex digits may be supplied.

\xhhMatch the character with two digit hex value hh.

\XMatch a Grapheme Cluster.

\ZMatch if the current position is at the end of input, but before the final line terminator, if one exists.

\zMatch if the current position is at the end of input.

\nBack Reference. Match whatever the nth capturing group matched. n must be a number ≥ 1 and ≤ total number of capture groups in the pattern.

\0oooMatch an Octal character. ooo is from one to three octal digits. 0377 is the largest allowed Octal character. The leading zero is required; it distinguishes Octal constants from back references.

[pattern]Match any one character from the pattern.

.Match any character. See dotMatchesLineSeparators and the scharacter expression in Table 4.

^Match at the beginning of a line. See anchorsMatchLines and the \mcharacter expression in Table 4.

$Match at the end of a line. See anchorsMatchLines and the m character expression in Table 4.

\Quotes the following character. Characters that must be quoted to be treated as literals are * ? + [ ( ) { } ^ $ | \ . /

Regular Expression Operators

Table 2 defines the regular expression operators.

Table 2

Regular Expression Operators

OperatorDescription

|Alternation. A|B matches either A or B.

*Match 0 or more times. Match as many times as possible.

+Match 1 or more times. Match as many times as possible.

?Match zero or one times. Prefer one.

{n}Match exactly n times.

{n,}Match at least n times. Match as many times as possible.

{n,m}Match between n and m times. Match as many times as possible, but not more than m.

*?Match 0 or more times. Match as few times as possible.

+?Match 1 or more times. Match as few times as possible.

??Match zero or one times. Prefer zero.

{n}?Match exactly n times.

{n,}?Match at least n times, but no more than required for an overall pattern match.

{n,m}?Match between n and m times. Match as few times as possible, but not less than n.

*+Match 0 or more times. Match as many times as possible when first encountered, do not retry with fewer even if overall match fails (Possessive Match).

++Match 1 or more times. Possessive match.

?+Match zero or one times. Possessive match.

{n}+Match exactly n times.

{n,}+Match at least n times. Possessive Match.

{n,m}+Match between n and m times. Possessive Match.

(...)Capturing parentheses. Range of input that matched the parenthesized subexpression is available after the match.

(?:...)Non-capturing parentheses. Groups the included pattern, but does not provide capturing of matching text. Somewhat more efficient than capturing parentheses.

(?>...)Atomic-match parentheses. First match of the parenthesized subexpression is the only one tried; if it does not lead to an overall pattern match, back up the search for a match to a position before the "(?>"

(?# ... )Free-format comment (?# comment ).

(?= ... )Look-ahead assertion. True if the parenthesized pattern matches at the current input position, but does not advance the input position.

(?! ... )Negative look-ahead assertion. True if the parenthesized pattern does not match at the current input position. Does not advance the input position.

(?<= ... )Look-behind assertion. True if the parenthesized pattern matches text preceding the current input position, with the last character of the match being the input character just before the current position. Does not alter the input position. The length of possible strings matched by the look-behind pattern must not be unbounded (no * or + operators.)

(?ismwx-ismwx:... )Flag settings. Evaluate the parenthesized expression with the specified flags enabled or -disabled. The flags are defined in Flag Options.

(?ismwx-ismwx)Flag settings. Change the flag settings. Changes apply to the portion of the pattern following the setting. For example, (?i) changes to a case insensitive match.The flags are defined in Flag Options.

Template Matching Format

The NSRegularExpression class provides find-and-replace methods for both immutable and mutable strings using the technique of template matching. Table 3 describes the syntax.

Table 3

Template Matching Format

CharacterDescriptions

$nThe text of capture group n will be substituted for $n. n must be >= 0 and not greater than the number of capture groups. A $ not followed by a digit has no special meaning, and will appear in the substitution text as itself, a $.

\Treat the following character as a literal, suppressing any special meaning. Backslash escaping in substitution text is only required for '$' and '\', but may be used on any other character without bad effects.

The replacement string is treated as a template, with $0 being replaced by the contents of the matched range, $1 by the contents of the first capture group, and so on. Additional digits beyond the maximum required to represent the number of capture groups will be treated as ordinary characters, as will a $ not followed by digits. Backslash will escape both $ and \.

Flag Options

The following flags control various aspects of regular expression matching. These flag values may be specified within the pattern using the (?ismx-ismx) pattern options. Equivalent behaviors can be specified for the entire pattern when an NSRegularExpression is initialized, using the NSRegularExpression.Options option flags.

Table 4

Flag Options

Flag (Pattern)Description

iIf set, matching will take place in a case-insensitive manner.

xIf set, allow use of white space and #comments within patterns

sIf set, a "." in a pattern will match a line terminator in the input text. By default, it will not. Note that a carriage-return / line-feed pair in text behave as a single line terminator, and will match a single "." in a regular expression pattern

mControl the behavior of "^" and "$" in a pattern. By default these will only match at the start and end, respectively, of the input text. If this flag is set, "^" and "$" will also match at the start and end of each line within the input text.

wControls the behavior of \b in a pattern. If set, word boundaries are found according to the definitions of word found in Unicode UAX 29, Text Boundaries. By default, word boundaries are identified by means of a simple classification of characters as either “word” or “non-word”, which approximates traditional regular expression behavior. The results obtained with the two options can be quite different in runs of spaces and other non-word characters.

Performance

NSRegularExpression implements a nondeterministic finite automaton matching engine. As such, complex regular expression patterns containing multiple * or + operators may result in poor performance when attempting to perform matches — particularly failing to match a given input. For more information, see the “Performance Tips” section of the ICU User Guide.

ICU License

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Topics

Creating Regular Expressions

init(pattern: String, options: NSRegularExpression.Options)

Returns an initialized NSRegularExpression instance with the specified regular expression pattern and options.

Declaration

init(pattern:String,options:NSRegularExpression.Options= [])throws

Parameters

pattern

The regular expression pattern to compile.

options

The regular expression options that are applied to the expression during matching. See NSRegularExpression.Options for possible values.

error

An out value that returns any error encountered during initialization. Returns an NSError object if the regular expression pattern is invalid; otherwise returns nil.firstMatchInString:options:range

Return Value

An instance of NSRegularExpression for the specified regular expression and options.

Discussion

Handling Errors In Swift:

In Swift, this API is imported as an initializer and is marked with the throws keyword to indicate that it throws an error in cases of failure.

You call this method in a try expression and handle any errors in the catch clauses of a do statement, as described in Error Handling in The Swift Programming Language and About Imported Cocoa Error Parameters.

Availability

iOS 4.0+

Mac Catalyst 13.0+

macOS 10.7+

tvOS 9.0+

watchOS 2.0+

See Also

regularExpressionWithPattern:options:error:

Getting the Regular Expression and Options

var pattern: String

Returns the regular expression pattern.

Declaration

varpattern:String{get}

Availability

iOS 4.0+

Mac Catalyst 13.0+

macOS 10.7+

tvOS 9.0+

watchOS 2.0+

See Also

regularExpressionWithPattern:options:error:

init(pattern:options:)

var options: NSRegularExpression.Options

Returns the options used when the regular expression option was created.

Declaration

varoptions:NSRegularExpression.Options{get}

Discussion

The options property specifies aspects of the regular expression matching that are always used when matching the regular expression. For example, if the expression is case sensitive, allows comments, ignores metacharacters, etc. See NSRegularExpression.Options for a complete discussion of the possible constants and their meanings.

Availability

iOS 4.0+

Mac Catalyst 13.0+

macOS 10.7+

tvOS 9.0+

watchOS 2.0+

See Also

regularExpressionWithPattern:options:error:

init(pattern:options:)

var numberOfCaptureGroups: Int

Returns the number of capture groups in the regular expression.

Declaration

varnumberOfCaptureGroups:Int{get}

Discussion

A capture group consists of each possible match within a regular expression. Each capture group can then be used in a replacement template to insert that value into a replacement string.

This value puts a limit on the values of n for $n in templates, and it determines the number of ranges in the returned NSTextCheckingResult instances returned in the match... methods.

An exception will be generated if you attempt to access a result with an index value exceeding numberOfCaptureGroups-1.

Availability

iOS 4.0+

Mac Catalyst 13.0+

macOS 10.7+

tvOS 9.0+

watchOS 2.0+

Searching Strings Using Regular Expressions

func numberOfMatches(in: String, options: NSRegularExpression.MatchingOptions, range: NSRange) -> Int

Returns the number of matches of the regular expression within the specified range of the string.

Declaration

funcnumberOfMatches(instring:String,options:NSRegularExpression.MatchingOptions= [],range:NSRange) ->Int

Parameters

string

The string to search.

options

The matching options to use. See NSRegularExpression.MatchingOptions for possible values.

range

The range of the string to search.

Return Value

The number of matches of the regular expression.

Discussion

This is a convenience method that calls enumerateMatches(in:options:range:using:).

Availability

iOS 4.0+

Mac Catalyst 13.0+

macOS 10.7+

tvOS 9.0+

watchOS 2.0+

See Also

rangeOfFirstMatch(in:options:range:)

matches(in:options:range:)

firstMatch(in:options:range:)

enumerateMatches(in:options:range:using:)

func enumerateMatches(in: String, options: NSRegularExpression.MatchingOptions, range: NSRange, using: (NSTextCheckingResult?, NSRegularExpression.MatchingFlags, UnsafeMutablePointer) -> Void)

Enumerates the string allowing the Block to handle each regular expression match.

Declaration

funcenumerateMatches(instring:String,options:NSRegularExpression.MatchingOptions= [],range:NSRange,usingblock: (NSTextCheckingResult?,NSRegularExpression.MatchingFlags,UnsafeMutablePointer) ->Void)

Parameters

string

The string.

options

The matching options to report. See NSRegularExpression.MatchingOptions for the supported values.

range

The range of the string to test.

block

The Block enumerates the matches of the regular expression in the string.

The block takes three arguments:

result

An NSTextCheckingResult specifying the match. This result gives the overall matched range via its range property, and the range of each individual capture group via its range(at:) method. The range {NSNotFound, 0} is returned if one of the capture groups did not participate in this particular match.

flags

The current state of the matching progress. See NSRegularExpression.MatchingFlags for the possible values.

stop

A reference to a Boolean value. The Block can set the value to true to stop further processing of the array. The stop argument is an out-only argument. You should only ever set this Boolean to true within the Block.

The Block returns void.

Discussion

This method is the fundamental matching method for regular expressions and is suitable for overriding by subclassers. There are additional convenience methods for returning all the matches as an array, the total number of matches, the first match, and the range of the first match.

By default, the Block iterator method calls the Block precisely once for each match, with a non-nil result and the appropriate flags. The client may then stop the operation by setting the contents of stop to true. The stop argument is an out-only argument. You should only ever set this Boolean to true within the Block.

If the reportProgress matching option is specified, the Block will also be called periodically during long-running match operations, with nil result and progress matching flag set in the Block’s flags parameter, at which point the client may again stop the operation by setting the contents of stop to true.

If the reportCompletion matching option is specified, the Block object will be called once after matching is complete, with nilresult and the completed matching flag is set in the flags passed to the Block, plus any additional relevant NSRegularExpression.MatchingFlags from among hitEnd, requiredEnd, or internalError.

progress and completed matching flags have no effect for methods other than this method.

The hitEnd matching flag is set in the flags passed to the Block if the current match operation reached the end of the search range. The requiredEnd matching flag is set in the flags passed to the Block if the current match depended on the location of the end of the search range.

The NSRegularExpression.MatchingFlags matching flag is set in the flags passed to the block if matching failed due to an internal error (such as an expression requiring exponential memory allocations) without examining the entire search range.

The anchored, withTransparentBounds, and withoutAnchoringBounds regular expression options, specified in the optionsproperty specified when the regular expression instance is created, can apply to any match or replace method.

If anchored matching option is specified, matches are limited to those at the start of the search range.

If withTransparentBounds matching option is specified, matching may examine parts of the string beyond the bounds of the search range, for purposes such as word boundary detection, lookahead, etc.

If withoutAnchoringBounds matching option is specified, ^ and $ will not automatically match the beginning and end of the search range, but will still match the beginning and end of the entire string.

withTransparentBounds and withoutAnchoringBounds matching options have no effect if the search range covers the entire string.

Availability

iOS 4.0+

Mac Catalyst 13.0+

macOS 10.7+

tvOS 9.0+

watchOS 2.0+

See Also

rangeOfFirstMatch(in:options:range:)

matches(in:options:range:)

numberOfMatches(in:options:range:)

firstMatch(in:options:range:)

func matches(in: String, options: NSRegularExpression.MatchingOptions, range: NSRange) -> [NSTextCheckingResult]

Returns an array containing all the matches of the regular expression in the string.

Declaration

funcmatches(instring:String,options:NSRegularExpression.MatchingOptions= [],range:NSRange) -> [NSTextCheckingResult]

Parameters

string

The string to search.

options

The matching options to use. See NSRegularExpression.MatchingOptions for possible values.

range

The range of the string to search.

Return Value

An array of NSTextCheckingResult objects. Each result gives the overall matched range via its range property, and the range of each individual capture group via its range(at:) method. The range {NSNotFound, 0} is returned if one of the capture groups did not participate in this particular match.

Discussion

This is a convenience method that calls enumerateMatches(in:options:range:using:) passing the appropriate string, options, and range.

Availability

iOS 4.0+

Mac Catalyst 13.0+

macOS 10.7+

tvOS 9.0+

watchOS 2.0+

See Also

rangeOfFirstMatch(in:options:range:)

numberOfMatches(in:options:range:)

firstMatch(in:options:range:)

enumerateMatches(in:options:range:using:)

func firstMatch(in: String, options: NSRegularExpression.MatchingOptions, range: NSRange) -> NSTextCheckingResult?

Returns the first match of the regular expression within the specified range of the string.

Declaration

funcfirstMatch(instring:String,options:NSRegularExpression.MatchingOptions= [],range:NSRange) ->NSTextCheckingResult?

Parameters

string

The string to search.

options

The matching options to use. See NSRegularExpression.MatchingOptions for possible values.

range

The range of the string to search.

Return Value

An NSTextCheckingResult object. This result gives the overall matched range via its range property, and the range of each individual capture group via its range(at:) method. The range {NSNotFound, 0} is returned if one of the capture groups did not participate in this particular match.

Discussion

This is a convenience method that calls enumerateMatches(in:options:range:using:).

Availability

iOS 4.0+

Mac Catalyst 13.0+

macOS 10.7+

tvOS 9.0+

watchOS 2.0+

See Also

rangeOfFirstMatch(in:options:range:)

matches(in:options:range:)

numberOfMatches(in:options:range:)

enumerateMatches(in:options:range:using:)

func rangeOfFirstMatch(in: String, options: NSRegularExpression.MatchingOptions, range: NSRange) -> NSRange

Returns the range of the first match of the regular expression within the specified range of the string.

Declaration

funcrangeOfFirstMatch(instring:String,options:NSRegularExpression.MatchingOptions= [],range:NSRange) ->NSRange

Parameters

string

The string to search.

options

The matching options to use. See NSRegularExpression.MatchingOptions for possible values.

range

The range of the string to search.

Return Value

The range of the first match. Returns {NSNotFound, 0} if no match is found.

Discussion

This is a convenience method that calls enumerateMatches(in:options:range:using:).

Availability

iOS 4.0+

Mac Catalyst 13.0+

macOS 10.7+

tvOS 9.0+

watchOS 2.0+

See Also

matches(in:options:range:)

numberOfMatches(in:options:range:)

firstMatch(in:options:range:)

enumerateMatches(in:options:range:using:)

Replacing Strings Using Regular Expressions

func replaceMatches(in: NSMutableString, options: NSRegularExpression.MatchingOptions, range: NSRange, withTemplate: String) -> Int

Replaces regular expression matches within the mutable string using the template string.

Declaration

funcreplaceMatches(instring:NSMutableString,options:NSRegularExpression.MatchingOptions= [],range:NSRange,withTemplatetempl:String) ->Int

Parameters

string

The mutable string to search and replace values within.

options

The matching options to use. See NSRegularExpression.MatchingOptions for possible values.

range

The range of the string to search.

template

The substitution template used when replacing matching instances.

Return Value

The number of matches.

Discussion

See Flag Options for the format of template.

Availability

iOS 4.0+

Mac Catalyst 13.0+

macOS 10.7+

tvOS 9.0+

watchOS 2.0+

See Also

stringByReplacingMatches(in:options:range:withTemplate:)

func stringByReplacingMatches(in: String, options: NSRegularExpression.MatchingOptions, range: NSRange, withTemplate: String) -> String

Returns a new string containing matching regular expressions replaced with the template string.

Declaration

funcstringByReplacingMatches(instring:String,options:NSRegularExpression.MatchingOptions= [],range:NSRange,withTemplatetempl:String) ->String

Parameters

string

The string to search for values within.

options

The matching options to use. See NSRegularExpression.MatchingOptions for possible values.

range

The range of the string to search.

template

The substitution template used when replacing matching instances.

Return Value

A string with matching regular expressions replaced by the template string.

Discussion

See Flag Options for the format of template.

Availability

iOS 4.0+

Mac Catalyst 13.0+

macOS 10.7+

tvOS 9.0+

watchOS 2.0+

See Also

replaceMatches(in:options:range:withTemplate:)

Escaping Characters in a String

class func escapedTemplate(for: String) -> String

Returns a template string by adding backslash escapes as necessary to protect any characters that would match as pattern metacharacters

Declaration

classfuncescapedTemplate(forstring:String) ->String

Parameters

string

The template string

Return Value

The escaped template string.

Discussion

Returns a string by adding backslash escapes as necessary to the given string, to escape any characters that would otherwise be treated as pattern metacharacters. You typically use this method to match on a particular string within a larger pattern.

For example, the string "(N/A)" contains the pattern metacharacters (, /, and ). The result of adding backslash escapes to this string is "\$N\\/A\$".

See Flag Options for the format of the resulting template string.

Availability

iOS 4.0+

Mac Catalyst 13.0+

macOS 10.7+

tvOS 9.0+

watchOS 2.0+

class func escapedPattern(for: String) -> String

Returns a string by adding backslash escapes as necessary to protect any characters that would match as pattern metacharacters.

Declaration

classfuncescapedPattern(forstring:String) ->String

Parameters

string

The string.

Return Value

The escaped string.

Discussion

For example, the string "(N/A)" contains the pattern metacharacters (, /, and ). The result of adding backslash escapes to this string is "\$N\\/A\$".

Availability

iOS 4.0+

Mac Catalyst 13.0+

macOS 10.7+

tvOS 9.0+

watchOS 2.0+

Custom Replace Functionality

func replacementString(for: NSTextCheckingResult, in: String, offset: Int, template: String) -> String

Used to perform template substitution for a single result for clients implementing their own replace functionality.

Declaration

funcreplacementString(forresult:NSTextCheckingResult,instring:String,offset:Int,templatetempl:String) ->String

Parameters

result

The result of the single match.

string

The string from which the result was matched.

offset

The offset to be added to the location of the result in the string.

template

See Flag Options for the format of template.

Return Value

A replacement string.

Discussion

For clients implementing their own replace functionality, this is a method to perform the template substitution for a single result, given the string from which the result was matched, an offset to be added to the location of the result in the string (for example, in cases that modifications to the string moved the result since it was matched), and a replacement template.

This is an advanced method that is used only if you wanted to iterate through a list of matches yourself and do the template replacement for each one, plus maybe some other calculation that you want to do in code, then you would use this at each step.

Availability

iOS 4.0+

Mac Catalyst 13.0+

macOS 10.7+

tvOS 9.0+

watchOS 2.0+

Constants

struct NSRegularExpression.Options

These constants define the regular expression options. These constants are used by the property options, regularExpressionWithPattern:options:error:, and init(pattern:options:).

struct NSRegularExpression.MatchingFlags

Set by the Block as the matching progresses, completes, or fails. Used by the method enumerateMatches(in:options:range:using:).

struct NSRegularExpression.MatchingOptions

The matching options constants specify the reporting, completion and matching rules to the expression matching methods. These constants are used by all methods that search for, or replace values, using a regular expression.

Relationships

Inherits From

NSObject

Conforms To

CVarArg

Equatable

Hashable

NSCopying

NSSecureCoding

NSRegularExpression

NSRegularExpression

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