12/17/2023 0 Comments Swift 3 convert string to double![]() ![]() To use the converted numbers you'll need to unwrap them-I recommend using the if let syntax for user input from a UITextField (or you can use the guard). There's no good number representation for a word like "alphabet", and the result becomes nil, which means that it's not a number. Without taking the locale into account, I write: valueAsString String(format: '.1f', value) // value 1.3 -> '1.3' valueAsDouble Double(valueAsString) // valueAsString '1.3' -> 1. ![]() let invalidNumber = Double("alphabet") // nil In swift, I would like to make conversions from number to string and back again without having to create a new formatter. That code would look like this: let theNumber '-6. For example, trying to convert from "alphabet" to a Double doesn't make sense. As pointed out in a now-deleted answer by Dwendel, you could also use the NSDecimalNumber initializer that takes a string, and you could then convert that to a Double. To round a Double with 3 digits precision, first multiply it by 1000, round it and divide the rounded result by 1000: let x 1.23556789 let y Double (round (1000 x) / 1000) print (y) /// 1.236. If the number is not valid, the conversion from String to Double isn't possible. You can use Swifts round function to accomplish this. If two strings are equal, the operator returns true. We use the operator to compare two strings. These String conversions can fail, because you're using a failable initializer for the Double, Float, or Int types. The String class in Swift provides various built-in functions that allow us to perform different operations on strings. 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 Swift specify double without converting to string. Converting a Double to a String produces Optional. 2 we can specify the precision for the string. The format string signifies that we are providing a floating point value f, and by passing in the. This can be done using String(format: '.2f', currency). 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. Convert optional string to double in Swift 3. We can convert it to a string and specify the level of accuracy that we would like from that value. ![]() 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). String with an Int, see the documentation comment for discussion. 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. Now add the following lines to cast and round the variable named double to an Int. 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. However, while that approach might work well for generating simpler descriptions of numbers that are under our complete control, we’ll likely going to need much more robust formatting strategies when dealing with dynamic numbers.In Swift 4 you get native String support for working with different numeric types (Float, Double, and Int). Solving the decimal problemĪt the most basic level, creating a textual representation of a given number simply involves initializing a String with it, which can either be done directly, or by using a string literal: let a = String( 42) // "42" let b = String( 3.14) // "3.14" let c = "\( 42), \( 3.14) " // "42, 3.14" So this week, let’s explore that topic, and how different kinds of numbers might warrant different formatting strategies. While working with numbers is one of those things that computers are inherently good at, we also occasionally need to format and present some of our numbers in a human-readable way, which can often be tricker than expected. Whether it’s in order to perform layout calculations, to schedule events using time intervals, or by dealing with our own, custom metrics, numbers really are everywhere. A significant part of any given app’s logic is likely going to involve working with numbers in one way or another. ![]()
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