Swift: dynamic strings with local variable injections

Question

Not sure if this is possible. But I want to do this:

let version = "2.0.1"
let year = 2017
let version = "Build \(version), \(year)"

However, I want to source the version string from a localised file. ie.

let version = "2.0.1"
let year = 2017
let versionTemplate = NSLocalizedString("version.template", comment:"")
let version = ???? // Something done with versionTemplate

I've looked at using NSExpression, but it's not obvious if it can do this or how.

Anyone does this?

Answer 1

Totally possible 😃

You'll want to use a String initializer rather than literals.

 let version = "2.0.1"
 let year = 2017
 let versionTemplate = String(format: NSLocalizedString("version.template", comment: ""), arguments: [version, year])
 // output: Build 2.0.1, 2017

In your localizable.strings file you need to have your template like this:

 "version.template" = "Build %@, %ld"

You can use a variety of format specifiers here. Check the documentation for all the possibilities. https://developer.apple.com/library/content/documentation/Cocoa/Conceptual/Strings/Articles/formatSpecifiers.html#//apple_ref/doc/uid/TP40004265-SW1