What is IoC (Inversion of Control)? Two pictures to help you figure it out!

The dependencies of component dependencies are provided by constructing injection, function calls or attribute settings. It's that simple.

Simple understanding of Inversion of Control (IOC, (Inversion of Control))

At first, our code dependencies may look like this, here are just examples There are cross-dependencies between three objects and three classes. The actual dependency relationship of our code is actually much more complicated. I can imagine the intersection of more than ten objects, and even horizontal intersection.

Now comes the problem , due to irresistible reasons, PHP version upgrade, requirement changes, etc., we need to replace the α object and delete the β object. How many code changes do we need to make?

It’s time to come up with the IOC .

Instantly refreshing.

The IOC container maintains a collection of object instances and class names globally. When we write a class, we The dependent objects are registered in the container, and are instantiated when the class is called.

This is the idea of ​​​​IOC. A system achieves "inversion of control" by completely separating organizational control and objects. For Dependency injection, which means achieving decoupling by controlling and instantiating dependent objects elsewhere in the system.

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