Objective-C转Swift遇类型转换错误：Range<String.Index>?无法转为NSRange

Got it, let's sort out this type conversion problem you're hitting when porting your Objective-C code to Swift.

Why the Error Happens #

In Objective-C, [NSString rangeOfString:] returns an NSRange directly—even when no match is found, it gives a range with location = NSNotFound and length = 0.

But in Swift, the String.range(of:) method returns a Range<String.Index>? (an optional value). This optional is nil if no match is found, and a valid Range if it does find a match. You can't directly assign this to an NSRange variable because they're incompatible types.

Solution 1: Convert Swift Range to NSRange (if you need NSRange for other logic) #

If you specifically need to work with NSRange, use the NSRange(_:in:) initializer to convert the Swift range, and handle the optional properly with guard or optional binding:

func combinedName() -> String? {
    // First check if we found a valid range
    guard let swiftRange = name.range(of: brand) else {
        return "\(brand) \(name)"
    }
    // Convert the Swift Range to NSRange
    let nsRange = NSRange(swiftRange, in: name)
    if nsRange.length > 0 {
        return name
    }
    return "\(brand) \(name)"
}

Solution 2: Use Swift's Native Range Logic (Simpler Approach) #

You don't actually need to convert to NSRange for this specific logic! Since a non-nil Range<String.Index> already means a match was found (so "length" is implicitly greater than 0), you can simplify the code entirely:

func combinedName() -> String? {
    // If the brand exists in the name, return the name as-is
    if name.range(of: brand) != nil {
        return name
    }
    // Otherwise, combine brand and name
    return "\(brand) \(name)"
}

Or even more concise with a ternary operator:

func combinedName() -> String? {
    return name.range(of: brand) != nil ? name : "\(brand) \(name)"
}

This matches the intent of your original Objective-C code perfectly, but follows Swift's optional handling best practices.

内容的提问来源于stack exchange，提问作者Siva