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Swift Trim Strings
Use Foundation to trim strings. Trim many characters in a set from the start and end of strings.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.
NSCharacterSet: 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.
Swift program that trims string
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)
Output
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.
SubstringA review. In Swift, strings are manipulated in many ways. With convenient methods like stringByTrimmingCharactersInSet, we avoid writing complex logic to eliminate characters.
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