I posted this post on our local iOS developer FB group. My app is kind of related to maths. result is always the same. Swift String interpolation in 5 minutes : Interpolation is the process to insert variables, constants, expressions, and literals into a string. It works with both single line and multiline strings. Follow. extension String. As a general note, there is an important difference between string interpolation vs the Printable protocol. 3 * … Swift String Interpolation Example Read More » This is also a requirement for the types used in string interpolation like this: "Integer value \(intVal) and double value \(doubleVal)" Why 'if let' does not seem to unbox a value as before in Swift 3 in Xcode 8.3 beta?-1. This is a more advanced topic, but I believe that not so many people are aware of this function in Swift, so let's talk a little bit about it. If you're thinking about things like JavaScript doing "x" + array , the equivalent in Swift is "x\(array)" . However I saw a comment in the code example in the SE saying that we shouldn’t call `appendLiteral` method directly but I see you call it in your appendInterpolation method implementation. Overview. Great blog post about a simple example for the new String Interpolation use cases in Swift 5. Question or problem in the Swift programming language: I can read an int, float, double as a string using string interpolation or String initializer. The Swift equivalent to what you're describing is string interpolation. Custom String interpolation. I'll show you a working example real quick. We have string interpolation right? "as My String into a series of statements similar to: var a: Int = 2 var c: Character = "e" var d: String = "\(a)\(c)" OR var d: String = String(a) + String(c) the … In Swift, types need to conform to the CustomStringConvertible protocol in order to be used inside strings. String Interpolation in Swift. Each entry of the string literal you inserted is wrapped in parentheses prefixed by a backslash: let x = 3 let str = "\\(x) * 5 = \\(Double(x) * 5)" print(str) Below is above code execution result. Custom string interpolation allows you to further optimize working with strings in Swift. 0. Check if variable is an Optional, and what type it wraps. Common use cases like printing JSON or optionals can make developing in Swift an even better experience. The main idea here is that you can create your own custom interpolation methods to format strings. And I want to display which input(s) is used to compute the result in a detailed label of a table view cell. Improving compiler performance with no real effort. For example ... You can use %@ in Swift's String(format:...), it can be substituted by a Swift String or any instance of a NSObject subclass. Creating a custom string becomes easy with string interpolation. 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