RegexBuilder · IOS API REFERENCE

TryCapture

struct · iOS 16.0+ · SDK 27.1

struct TryCapture<Output>

A regex component that attempts to transform a matched substring, saving the result if successful and backtracking if the transformation fails. You use a `TryCapture` component to capture part of a match as a transformed value, when a failure to transform should mean the regex continues matching, backtracking from that point if necessary. The code below demonstrates using `TryCapture` to include a test that the `Double` value of a capture is over a limit. In the example, `regex` matches a dollar sign (`"$"`) followed by one or more digits, a period (`"."`), and then two additional digits, as long as that pattern appears at the end of the line. The `TryCapture` block wraps the digits and period, capturing that part of the match separately and passing it to its `transform` closure. That closure converts the captured portion of the match, converts it to a `Double`, and only returns a non-`nil` value if it is over the transaction limit. let transactions = """ CREDIT 109912311421 Payroll $69.73 CREDIT 105912031123 Travel $121.54 DEBIT 107733291022 Refund $8.42 """ let transactionLimit = 100.0 let regex = Regex { "$" TryCapture { OneOrMore(.digit) "." Repeat(.digit, count: 2) } transform: { str -> Double? in let value = Double(str)! if value > transactionLimit { return value } return nil } Anchor.endOfLine } When the `TryCapture` block's `transform` closure processes the three different amounts in the list of transactions, it only returns a non-`nil` value for the $121.54 transaction. Even though the capture returns an optional `Double` value, the captured value is non-optional. // The type of each match's output is `(Substring, Double)`. for match in transactions.matches(of: regex) { print("Transaction amount: \(match.1)") } // Prints "Transaction amount: 121.54" Throwing an error from a `transform` closure aborts matching and propagates the error out to the caller. If you want to capture the `nil` results of a failable transformation, instead of continuing a search, use ``Capture`` instead of `TryCapture`.

Members (0)

This type has no directly callable members in this snapshot. See the framework’s skipped declarations for unsupported APIs.

Skipped declarations

44 declarations were excluded from these bindings. Each reason comes from the generator or the iOS SDK compiler.

TryCapture.init(_:transform:)

This declaration needs Swift generic type arguments. (no canonical witness for W)

TryCapture.init(_:as:transform:)

This declaration needs Swift generic type arguments. (no canonical witness for W)

TryCapture.init(_:transform:)

callback cannot propagate synchronous failure

TryCapture.init(as:_:transform:)

callback cannot propagate synchronous failure

TryCapture.init(_:transform:)