Trim. Often strings contain whitespace (like spaces or newlines) at their starts or ends. These characters are often removed or trimmed.
In Foundation, we locate a useful method called stringByTrimmingCharactersInSet. A character set is required. The result is a string with the specified characters removed.
An example. Let us begin with a simple example. We introduce a "source" string that contains a leading space, and a trailing period and space.
Detail We create a NSCharacterSet with three characters—a space, period, and a question mark.
Next We invoke the trim method, stringByTrimmingCharactersInSet. We pass the set instance as an argument.
Result The string returned has no leading or trailing spaces (and no period). The endIndex values indicate 3 characters were removed.
import Foundation
// The string we are trimming.
let source = " Areopagitica, John Milton. "// Create a character set of chars to trim.
let set = NSCharacterSet(charactersInString: " .?")
// Call func with character set.
let result = source.stringByTrimmingCharactersInSet(set)
// Write the result.
print(result)
// Print before and after lengths.
print(source.endIndex)
print(result.endIndex)Areopagitica, John Milton
28
25
An alternative. A custom pair of loops (for startIndex and endIndex) could be written. In these, we continue towards the center of a string as removable characters are encountered.
Then We take a substring (of the inner part of the string) to perform the trimming operation.
A review. In Swift, strings are manipulated in many ways. With convenient methods like stringByTrimmingCharactersInSet, we avoid writing complex logic to eliminate characters.
Dot Net Perls is a collection of tested code examples. Pages are continually updated to stay current, with code correctness a top priority.
Sam Allen is passionate about computer languages. In the past, his work has been recommended by Apple and Microsoft and he has studied computers at a selective university in the United States.