Running methods with returned objects

I am brushing up on my non-framework Object Oriented PHP and decided to do a test. Unfortunately, while I understand the concept of calling methods from a class, this particular test is slightly more complicated and I don't know what the terminology is for this particular type of situation is.

Test

Create a PHP class that parses (unknown number of) text files in a folder and allows to extract the total value of amount field from the file and get filenames of parsed files.

File Format:

The files are plain text csv files. Let's assume that the files contain a list of payments changed in the last N days. There are 2 different types of line:

• Card payment collected - type = 1, date, order id, amount
• Card payment rejected - type = 2, date, order id, reason, amount

Example file:

1,20090313,542,11.99

1,20090313,543,9.99

2,20090312,500,some reason, 2.99

Usage Example:

The usage could be something like this:

$parser = new Parser(...);
$files = $parser->getFiles();

foreach ($files as $file) {
    $filename = $file->getFileName();
    $amount_collected = $file->getTotalAmount(...); 
    $amount_rejected = $fi开发者_如何学编程le->getTotalAmount(...);
}

My question is:

How can you do $file->method() when the class is called parser? I'm guessing you return an object from the getFiles method in the parser class, but how can you run methods with the returned object?

I attempted to Google this, but as I don't know the terminology for this situation I didn't find anything.

Any help is much appreciated, even if it's just what the terminology for this situation is.

The returned object could be of class ParserFile with getFileName and getTotalAmount methods. This approach would be quite close to the Factory pattern, although it would be a good idea to make the getFiles method static, callable without the parser class itself.

class ParserFile {
    public function getFilename() { /* whatever */ }
    public function getTotalAmount() { /* whatever */ }
}

class Parser {
    public static function getFiles() {
        // loop through the available files
        // and store them in some $arr
        $arr[] = new ParserFile('filename1.txt');
        $arr[] = new ParserFile('filename2.txt');

        return $arr;
    }
}

$files = Parser::getFiles();
foreach ($files as $file) {
    $filename = $file->getFilename();
    $amount_collected = $file->getTotalAmount();
    $amount_rejected = $file->getTotalAmount();
}

Although I'm pretty sure this is not the best design. Another approach would be:

$parser = new Parser();
$files = $parser->getFiles();
foreach ($files as $file) {
    $filename = $parser->getFilename($file);
    $amount_collected = $parser->getTotalAmount($file);
    $amount_rejected = $parser->getTotalAmount($file);
}

So you'll get the array of files into your $files but when you want to parse these files you'll ask $parser to do it for you by passing the current $file to its methods.

There's no 100% correct solution I guess, just use what's best for you. If you then encounter problems, profile, benchmark and refactor.

Hope that helped. Cheers :)

P.S. Hope this isn't homework :D