Replace. A string has a range of characters we want to change. With replaceSubrange we can replace them with another string. We use index() to create a range.
Method notes. When replacing strings in Swift, we often combine multiple methods. We combine index() and replacement methods like replaceSubrange.
Example program. In this program we first declare a string. This string has a substring "red" in it. We next call replaceSubrange with a range.
Detail We pass a range to replaceSubrange. We use index() on the string to get the bounds. We advance 6 chars.
Detail We use a range operator to advance to 9 chars into the string. We base the end also on the startIndex.
Result ReplaceSubrange changes the string "red" in the string to "yellow." The string remains colorful.
var value = "green red blue"
print(value)
// Replace range at positions 6 through 9.// ... Specify a replacement string.
let start = value.index(value.startIndex, offsetBy: 6);
let end = value.index(value.startIndex, offsetBy: 6 + 3);
value.replaceSubrange(start..<end, with: "yellow")
print(value)green red blue
green yellow blue
Change chars. This program loops through the chars in a string. It then uses an if-else block to change some chars in the string. The value "1" is changed.
Detail This method adds a char to a string. We build up a new string in the for-loop.
var value = "123abc123"
var result = String()
// Replace individual characters in the string.// ... Append them to a new string.for char in value.characters {
if char == "1" {
let temp: Character = "9"
result.append(temp)
}
else {
result.append(char)
}
}
print(result)923abc923
ReplacingOccurrences. In Foundation we find some string replacement methods. With replacingOccurrences we replace all occurrences of one substring with another.
Here We change the word "cats" to "birds." This might make the "dogs" part happier.
import Foundation
let text = "cats and dogs"// Replace cats with birds.// ... Use Foundation method.
let result = text.replacingOccurrences(of: "cats", with: "birds")
// Print result.
print(result)birds and dogs
ReplacingCharacters. Here we use replacingCharacters. This may have the same effect as the replaceSubrange method in Swift. It replaces a range with a substring.
import Foundation
let letters = "zzzy"// Replace first three characters with a string.
let start = letters.startIndex;
let end = letters.index(letters.startIndex, offsetBy: 3);
let result = letters.replacingCharacters(in: start..<end, with: "wh")
// The result.
print(result)why
A review. Strings in Swift are accessed through ranges, along with startIndex and endIndex. To replace chars, we access a range and invoke replaceSubrange.
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.