Example code for article about ArgumentParser - Validation

Validation.swift

// 1
func validate() throws {
    let filePathWithExtension = "\(filePath)\(fileExtension)"
    // 2
    if FileManager.default.fileExists(atPath: filePathWithExtension) && force == false {
        // 3
        throw ValidationError("Given file already exists. To override it, please add `--force`.")
    }
}