extension String. This is also a requirement for the types used in string interpolation like this: "Integer value \(intVal) and double value \(doubleVal)" Overview. String interpolation is a way to construct new strings that contain constants, variables, literals, and expressions. Check if variable is an Optional, and what type it wraps. Why 'if let' does not seem to unbox a value as before in Swift 3 in Xcode 8.3 beta?-1. "as My String into a series of statements similar to: In Swift, types need to conform to the CustomStringConvertible protocol in order to be used inside strings. And I want to display which input(s) is used to compute the result in a detailed label of a table view cell. 0. We have string interpolation right? 3 * … Swift String Interpolation Example Read More » Custom string interpolation allows you to further optimize working with strings in Swift. Swift 3 incorrect string interpolation with implicitly unwrapped Optionals. The Swift equivalent to what you're describing is string interpolation. Custom String interpolation. Follow. Question or problem in the Swift programming language: I can read an int, float, double as a string using string interpolation or String initializer. 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. The main idea here is that you can create your own custom interpolation methods to format strings. 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. 13. Common use cases like printing JSON or optionals can make developing in Swift an even better experience. Each Expressible By String Interpolation type has an associated String Interpolation type which conforms to String Interpolation Protocol.Swift converts an expression like "The time is \(time). If you're thinking about things like JavaScript doing "x" + array , the equivalent in Swift is "x\(array)" . I'll show you a working example real quick. Steven Curtis. My app is kind of related to maths. 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. Improving compiler performance with no real effort. result is always the same. As a general note, there is an important difference between string interpolation vs the Printable protocol. 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. String Interpolation in Swift. var a: Int = 2 var c: Character = "e" var d: String = "\(a)\(c)" OR var d: String = String(a) + String(c) the … Great blog post about a simple example for the new String Interpolation use cases in Swift 5. 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