Recently I took the regex course at executeprogram.com. Awesome stuff.

As you know, as soon as you have a slight idea what regex is, you try to use it everywhere. Yesterday I needed to change all strings of double values in a JSON into double values. For example I wanted to replace "1.23" with 1.23.

Regex without the \d+.*?\w

If you don’t know regular expressions but still need more than just replace a simple string with another simple string, Xcode has you covered.

As an example lets say we’d like to change all the properties in the following struct into optionals:

struct ChemElement : Codable, Equatable {
  let abbreviation: String
  let atomMass: Double
  let electronConfiguration: String
  let group: String
  let name: String
  let ordinal: Int
  let period: Int
  let yPos: Int
  let title: String
  let pauling: String
  let mostImportantRadioactiveIsotope: Int
  let decayType: String
  let lifetime: String
  let phaseNorm: String
  let crystalStructure: String
}

(Please don’t judge this code. I’m still refactoring. ;) )

We activate search with ⌘-f. In the search bar is a plus sign. When you click it, you can select different elements to search for. The patterns we need is let Word: Word. The matching substrings are highlighted in the editor:

If you look closely you can see there is a small number next to the pattern elements:

In the Replace text field you can refer to the different matches using a $ sign and the number next to the pattern part like this: var $1: $2?. In Xcode this looks like this:

When we now click the All button, all the properties are changed into optional properties:

struct ChemElement : Codable, Equatable {
  var abbreviation: String?
  var atomMass: Double?
  var chemieBool: Bool?
  var electronConfiguration: String?
  var group: String?
  var name: String?
  var ordinal: Int?
  var period: Int?
  var yPos: Int?
  var title: String?
  var pauling: String?
  var mostImportantRadioactiveIsotope: Int?
  var decayType: String?
  var lifetime: String?
  var phaseNorm: String?
  var crystalStructure: String?
}

Search using regular expressions

If you know regular expressions you can activate it in search by clicking the drop down that shows Contains and change it into Regular Expression:

Than you can use regular expressions when searching:

But if you’d like to use matches in Replace like you did above you need to add parentheses like this:

Thanks for reading!

If you have comments about this or in case I missed something, you can find me on Twitter.