1. What is a regular expression
Regular expression, also known as regular expression, regular expression (English: Regular expression, often abbreviated as regex, regexp or RE in code), is a concept of computer science.
Regular expressions use a single string to describe and match a series of strings that conform to a certain syntactic rule.
In many text editors, regular expressions are usually used to retrieve and replace text that conforms to a certain pattern.
2. Character composition of regular expressions
Ordinary characters [a~z], special characters (called "metacharacter")
3. Support
Almost all programming languages support regular expressions, such as: OC, swift, java, c#, python, js, etc.
In many text editors, regular expressions can be used for searching, and Xcode also supports regular expressions!
4. Use
- match
(pattern) Match pattern and get this match. The obtained match can be obtained from the generated Matches collection
- gather
[xyz] Character set (x||y||z)
[a-z] Character range a-z
[a-zA-Z] Character range a-z A-Z
[^xyz] Negative value character set (any character except xyz)
[^a-z] Negative value character range
[a-d][m-p] union (a to d or m to p)
- Common metacharacters
. Match any character other than line break
\w Match letters or numbers or underscores or Chinese characters [a-zA-Z_0-9]
\s Match any whitespace characters (space, TAB\t, Enter\r\n)
\d Match number [0-9]
^a matches the start a character of the string
a$ matches the end of the string a character
\bw Match the beginning or end of a word w character
- Commonly used antonyms
\W Match any characters that are not letters, numbers, underscores, and Chinese characters [^\w]
\S Match any character that is not a whitespace character [^\s]
\D Match any non-numeric characters [^0-9]
\Ba Matches a character that is not the position at which the word starts or ends
[^a] Match any character other than a
[^aeiou] Match any character except the letters aeiou
- Commonly used qualifiers
w*oo repeat zero or more times
w+oo Repeat once or more times
w?oo Repeat zero or once
w{n} w repeat n times
w{n,} w repeat n times or more
w{n,m} w repeat n to m times
- Greed and lazy
*? Repeat any time, but repeat as few as possible
*+ Repeat 1 or more times, but as few as possible
?? Repeat 0 or 1 time, but repeat as little as possible
w{1,2}? Repeat 1 to 2 times, but repeat as few as possible
ww{1,}? Repeat more than 1 time, but repeat as few as possible
5. Example
//Judge QQ number (regular judgment) fileprivate func checkIsQQNumber(str:String) ->Bool {
// 1. Determine whether it starts with 0 if ("0"){
return false
}
// 2. Determine whether it is 5~15 digits if < 5 || > 15{
return false
}
// 3. Determine whether all are numbers for c in {
if c < "0" || c > "9"{
return false
}
}
return true
}
// Regularly determine the mobile phone number fileprivate func checkPhoneNumber(str:String)->Bool {
let pattern = "1[3578]\\d{9}"
let regex = try! NSRegularExpression(pattern: pattern, options: (rawValue:0))
let res = (in: str, options: (rawValue:0), range: NSMakeRange(0, ))
if > 0 {
return true
}
return false
}
Summarize
The above is the implementation code of swift 3.0 regular expression search/replace character introduced to you by the editor. I hope it will be helpful to you. If you have any questions, please leave me a message and the editor will reply to you in time. Thank you very much for your support for my website!