For example, trying to convert from "alphabet" to a Double doesn't make sense. If the number is not valid, the conversion from String to Double isn't possible. These String conversions can fail, because you're using a failable initializer for the Double, Float, or Int types. Watch an easy to follow video describing how to use NumberFormatter.Explore the code in the Swift Playground (Swift 4).Print the String to Double Cheatsheet for quick reference.Not everyone learns the same way, get the String Conversion Toolkit so that you can follow along with this guide. How do you use the value if it's wrapped in an optional type? Get the String Conversion Toolkit let wholeNumber = Int("27")īut that's not everything you need to know, because this conversion process can fail, and that gives you an optional Double (i.e. Use Int and the variants like Int32, UInt64, etc. Let width = CGFloat(Double("200.0")!) Convert Swift String to Int Use Double, Float, CGFloat to convert floating-point values (real numbers). Grab the String to Double Cheatsheet and Swift Playground mentioned below in the toolkit for a quick reference that you can use as you work on your apps. Plus you'll learn about a word of caution when converting to NSString to use the doubleValue property. In this String to Double Guide, you'll learn how to convert different types of String values and how to handle edge cases. But that's not the end of the story, you may need to use the NumberFormatter (NSNumberFormatter) class to convert formatted numbers (1,000,000) or currency ($3.50) in your Swift code. In Swift 4 you get native String support for working with different numeric types (Float, Double, and Int).
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