String.hasPrefix() / hasSuffix() / contains()

// Prefix match
string.hasPrefix("prefix")

// Suffix match
string.hasSuffix("suffix")

// Substring match
string.contains("search string")

// Range search
string.range(of: "search string")

// Case-insensitive search
string.localizedStandardContains("search string")

// hasPrefix and hasSuffix
let filename = "report_2026.pdf"
print(filename.hasPrefix("report"))  // true
print(filename.hasSuffix(".pdf"))    // true
print(filename.hasSuffix(".txt"))    // false

let url = "https://example.com/page"
if url.hasPrefix("https://") {
    print("Secure connection")
}

// contains
let message = "Swift is a type-safe language"
print(message.contains("type-safe"))    // true
print(message.contains("dynamically typed")) // false

// Getting the position with range(of:)
let text = "Hello, World!"
if let range = text.range(of: "World") {
    print("Found: \(text[range])")
    // Get the substring after the match
    print("Remainder: \(text[range.upperBound...])")
}

// Case-insensitive search
let html = "<a href='Link?lang=en'>text</a>"
if html.range(of: "link", options: .caseInsensitive) != nil {
    print("'link' found (case-insensitive)")
}

// Filtering multiple files
let files = ["photo.jpg", "doc.pdf", "image.png", "report.pdf", "video.mp4"]
let pdfs = files.filter { $0.hasSuffix(".pdf") }
print(pdfs)  // ["doc.pdf", "report.pdf"]

hasPrefix, hasSuffix, and contains all handle Unicode correctly and perform locale-independent comparisons. To ignore case, use range(of:options:.caseInsensitive) or localizedStandardContains.

range(of:) returns a Range<String.Index> for the matched position. Swift string indices are of type String.Index, not Int. You cannot access characters using integer offsets directly.

For string replacement and trimming, see string.replacingOccurrences() / trimmingCharacters().