Swift Padding String Example (toLength)

Add padding to a String with the padding method and the toLength, withPad, startingAt arguments.

Padding. Sometimes a String needs to be a certain number of characters long. It must fill an entire text field. With padding methods, we can add characters to a String.

In Foundation, we find a method called padding() with 3 arguments. We specify a string that is added to fill the desired length. This pads a string.

First example. To begin, we introduce a String that has 4 characters (cats). We then invoke the padding() method. We use 3 arguments.

ToLength: We pass 10 to expand the string to a width of 10 characters. The resulting string will have 10 chars in its padded form.

WithString: This string is used to create the padding. It is repeated to fill the desired length.

Swift program that uses padding on string import Foundation // An example string. let cats = "cats" // Pad to length 10. let padded = cats.padding(toLength: 10, withPad: " ", startingAt: 0) // Write result. print("Padded = |\(padded)|") // Print before and after lengths. print(cats.endIndex) print(padded.endIndex) Output Padded = |cats | Index(_base: Swift.String.UnicodeScalarView.Index(_position: 4), _countUTF16: 0) Index(_base: Swift.String.UnicodeScalarView.Index(_position: 10), _countUTF16: 0)

Different characters. With the padding() method, we can pad with different characters. A space is a common padding char, but here we use a hyphen to pad a string.

Swift program that pads with hyphen character import Foundation // A string. let id = "X1" // Pad with hyphens. let padded = id.padding(toLength: 4, withPad: "-", startingAt: 0) // Uses hyphen as padding character. print(padded) Output X1--

Some notes. In Swift, strings can be hard to manipulate. But we usually do best by choosing the most specific Foundation method possible.

And: We could apply padding by adding space chars, but this is more complex. A single Foundation call is clearer.

Swift 3 changes. In Swift 3 we use padding() instead of stringByPaddingToLength. The method call is simpler, and the arguments are labeled differently.

A review. Padding increases the length of a String to fill a field. This can be used to ensure a string meets a length requirement. It can be used sometimes for text justification.

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Swift Padding String Example (toLength)

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