Then XCTest runs every test case and reports the status of the test case. A test log starts and ends with the status of a test suite. I have been writing a script to parse the logs from running XCTest-based unit tests. To show you how you can apply Swift Regex to your workflow, let's work out an example together. This is a really big deal because you can create Regexes out of existing battle-tested parsers that take care of corner cases and support localization, and compose them with the expressivity of the Regex builder DSL. For example, to parse a bank statement like this, I can use a Foundation-provided date parser with a custom format and a currency parser with a domain-specific parse strategy. With Regex support in Foundation, you can embed the Foundation parsers directly in Regex builder. This year, Foundation is adding support for formatting and parsing URLs as well. If you want to learn more about these APIs, watch the What's new in Foundation session from WWDC21. The Regex support in Foundation is none other than the formatters and parsers that you are probably already using, such as those for Date and Number. Finally, on top of Regex builder and Regex-powered algorithms, this year, Foundation introduced its own Regex support that works seamlessly with Regex builder. Also, Regex can now be used in Swift's pattern matching syntax in control flow statements, making it easier than ever to switch on strings. Besides matching, the Swift standard library also added APIs for Regex-based predication, replacement, trimming, and splitting. Regex-powered algorithms are collection-based APIs that provide some of the most common operations such as first match, which finds the first occurrence of a Regex in a string, 'wholeMatch', which matches the entire string against a Regex, 'prefixMatch', which matches the prefix of a string against a Regex. With Regex built on its underlying Regex engine, the Regex builder DSL and Regex-powered algorithms expand the power and expressivity of Regex. In the rest of this session, I will explain a bit more about this execution model. As we reach the end of the string, matching succeeds. So the Regex engine moves to the next pattern in the Regex, to match one or more digits. At this point, it reaches character "1" and tries to match this character against character "a". First, it matches one or more of character a. The Regex engine will start from the first character of the input. I use one of the matching algorithms, 'wholeMatch', to match input "aaa12".
This Regex matches a string that starts with one or more of letter "a" followed by one or more digits. Let's take a look at a very simple Regex. When executing a Regex, the Regex engine takes an input string, and performs matching from the start to the end of the string. A Regex is a program that is to be executed by its underlying Regex engine. In this session I will show you how Regex works and how you can apply Regex in your workflow. With Regex builder, reading the content of a Regex is as easy as reading native Swift API. But for ultimate readability and customizations, I can use the Regex builder DSL. Because my Regex string is known at compile-time, I can switch to using a Regex literal so that the compiler would check for syntax errors and Xcode can show syntax highlighting. I can then use string's 'firstMatch' algorithm to find the first occurrence of the pattern defined by this Regex, and print the whole match, just like that.
This is a new type in the Swift Standard Library. It matches "user_id" colon followed by zero or more whitespaces followed by one or more digits What's different this time is that we are creating a value of type Regex. I can create a regular expression from text like I normally do with 'NSRegularExpression'. Let's say I have a string of data, and like to match and extract the user ID from this string. Let's look at a very simple example of Swift Regex. It is a domain-specific language, or DSL, that takes advantage of the syntactic simplicity and composability of result builders, and pushes the readability of Regex to a whole new level.įor background as to why Swift Regex makes it easier to process strings, check out the Meet Swift Regex session by my colleague Michael. And finally, a result builder API called RegexBuilder. A language built-in Regex literal syntax, which makes this powerful and familiar concept even more first-class. They start with the 'Regex' type, a new type in the Swift Standard Library. Swift 5.7 is gaining powerful new capabilities for string processing. Today, let's embark on a journey beyond the basics of Swift Regex. ♪ ♪ Hi, I'm Richard, I'm an engineer on the Swift Standard Library team.
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