Whats Magento Dependency Injection Doing? TRY THIS

A really complex area in Magento is the dependency injection layer. There's a lot going on. Object Manager does a lot of magic behind the scenes and it can be a little bit difficult to figure out what's going on at certain stages. Luckily, there's a little known tool built right in Magento in the Bin Magento script called Dev di Info and it does a lot of cool things. Let's take a look and see how it works. So I will open up Terminal and then just run bin slash Magento dev di info and then we need to pass a class or interface as an argument to this command and we need to pass it in as a string. So let's add some double quotes here and then pass in a class I'm going to pass in Magento Catalog UI Data Provider Product Listing Data Provider. Now if you guessed this is a class that provides data to the product Listing Magento Catalog UI component and if we go ahead and execute this command, the the result that we will get is the DI configuration for this class which includes the preference that is used, all of the constructor parameters and their configured default values, as well as any plugins that actually hook into this class or the preference that's related to this class. So let's confirm at least these constructor parameters by opening up this file. And we can do that with command O and and then we can just paste in this class and open it. And when we take a look at the constructor parameters, this has name reporting, search criteria builder and so on, and then two empty arrays for meta and data. So if we again look at the output of that command, it will exactly match those available constructor parameters. Next let's look at one of these plugins that's actually hooking into this class and we can grab this Magento wishlist plugin and that is the data provider for wishlist settings. So let's go ahead and copy this and go ahead and open up this class. And again looking at the command, it tells us that it's hooking into the get data method and it is an after plugin. So when we go ahead and look at this function, it is after get data. So it's definitely hooking in to this specific data provider. And we can see that this is simply adding a value to this result array. We can also take a look at how this command works with interfaces. So if we go ahead and inspect this class and then go to the etc di XML file, we will see a preference defined in this di.xml file and that is a preference for the wishlist provider interface and it's passing in this controller wishlist provider class. So let's go ahead and take this interface and copy it, open up terminal and then we will again run bin slash magento dev di info and pass in this interface as a string. So when we take a look at this command we will see that there are no plugins that hook into it, but we will find the preference for this interface which is this wishlist provider class. If you are looking at an interface and wondering what exact class is is taking precedence, this is a great method to use because it'll always return the corresponding class reference. This command can really help you out when you are knee deep in debugging a specific task and are just wondering what's going on with the DI layer. If you want to know about a few other neat dev tools for Magento, check out this video which has a few more in it.