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Basics of Object Design - Part One

Oliver Mensah on January 29, 2019

In my previous post, Basics of Object Design Series, I shared about the book I have been reading on object design, Style Guide for Object Design by...

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Bajzáth Dávid • Jan 30 '19

Really nice write up, thank you! 👍
I have only one complaint, with the "Do nothing in the constructor function, Only assign properties" part.
I think in the first solution (extracting to a method) it could be called from the constructor, this is what I usually do if it is not a complicated task. This way it only runs once, and the constructor is the place where you should prepare all of your dependencies, like you said above.
The second method (expecting bootstrapping) adds a hidden dependency, as the logging will fail if the file is not present. Moving it out of the class can be a good idea (especially if it is complex), but I would move it to a Factory class, and make the FileLogger constructor only visible to that class.
I would love to hear your opinion on this.

Oliver Mensah • Jan 30 '19

Yeah. You can absolutely call that in the constructor as well to make it run once on the entire object. That would be a good approach to do a sanity check before logging. Thanks for the feedback.

For the second approach with bootstrapping, the dependency is still not hidden. Just that we pass it from the bootstrap face. There are some exceptions that might happen with this, so you will need to throw some exception depending on the issue that might occur. The article just focussed on only one exception type but there are others that we can also look at.

Great feedback.

Bajzáth Dávid • Jan 30 '19

Thank you for your answer!

I meant hidden as you can create a FileLogger instance without error even if you do not create the file for it, and it will only fail when the first logging takes place, not at creation time.

Oliver Mensah • Jan 30 '19

Thank you for the explanation. Very much appreciated

Oliver Mensah • Jan 30 '19

Can you show your proposed solution in code? I mean that of the second method, bootstrapping.

Bajzáth Dávid • Jan 30 '19 • Edited

I wrote PHP code years ago, but I forgot it does not have nested classes like Java, that is what I was referencing with "make the FileLogger constructor only visible to that class", but you can do a similar thing if you make the constructor protected and move the Factory class to the same package.

final class FileLogger{
    private $logFilePath;
    protected function __construct(string $logFilePath){
        $this->logFilePath = $logFilePath;
    }
    public function log(): void{
        $this->ensureLogFileExists();
    }

}

final class FileLoggerFactory {

    public function create(string $logFilePath): FileLogger {
        ensureLogFileExists($logFilePath);
        return new FileLogger($logFilePath);
    }

    private function ensureLogFileExists(string $logFilePath): void{
        if (is_file($logFilePath)) {
            return;
        }
        $logFileDirectory = dirname($logFilePath);
        if (!is_dir($logFileDirectory)) {
            // create the directory if it doesn't exist yet
            mkdir($logFileDirectory, 0777, true);
        }
        touch($logFilePath);
    }
}

Also, I am new here and I have no idea how to have syntax highlight :(

Oliver Mensah • Jan 31 '19 • Edited

I have seen the approach as well. Thanks. So allowing the Factory object to new up the object.

For the code highlighting, you can use
3start-backticts
langauge(php, js, py, etc)

3end-backticks

Aleksi Kauppila • Jan 29 '19

Very nice post! 👍 👍 these are very important practices to keep the program understandable and consistent. I also think that emphasizing reusability is not that important compared to introducing MEANING into the application.

I wrote about setters a while ago and it touches this same subject: dev.to/aleksikauppila/discarding-s...

Oliver Mensah • Jan 29 '19

I will have a look at your work as well. Thanks for the feedback.
I think both would be well achieved having the fundamentals right. Also, think introducing the meaning into the application is really important.

Aleksi Kauppila • Jan 29 '19

Yes, both reusability and meaning are achieved with the examples in this article 👍

Bet Vill • Nov 22 '21

Great article and very handy to have it broken down in parts, easy to read because everything is constructed in a logical way. All content is approved just like in read this article and you will be convinced of the quality of the content itself as well as of your programmes))

Alex Jones • Jul 31 '20

A good article, although this is not really my specialization, but it became a source Top Online Casinos in Australia site reworking, under the principles you described, I will not say that it was easy, but we managed it.