How are the 'Counter' function and 'notFound' function used to implement the 'Handler' interface?

Function Implementing Interface

The Problem

In the provided code, we define an interface "Handler" with a single method "ServeHTTP". Subsequently, two functions are presented:

1. An implementation of "Handler" with a "ServeHTTP" method called "Counter".
2. A function "notFound" that implements "HandlerFunc", which is then converted into an instance of "Handler" using "HandlerFunc".

The question arises: how do these functions fit together and implement the "Handler" interface?

The Answer

"Handler" Interface:

The "Handler" interface mandates that any type implementing it must have a "ServeHTTP" method with specific arguments.

"Counter" Function:

The "Counter" function adds a "ServeHTTP" method to the "Counter" type, fulfilling the interface requirements.

"HandlerFunc" Type and "notFound" Function:

"HandlerFunc" is a function type that matches the signature of "Handler"'s "ServeHTTP" method. The "notFound" function satisfies this function type.

Converting Function to Implement Interface:

To make the "notFound" function compatible with the "Handler" interface, it is assigned to an instance of "HandlerFunc". The "ServeHTTP" method for this instance invokes the "notFound" function with the appropriate arguments.

Result:

By converting "notFound" to "HandlerFunc" and creating an instance, it effectively implements the "Handler" interface, allowing "Handle404" to be used seamlessly with the interface.

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