What\'s the Difference Between a Receiver and Parameters in Go Methods?

The Receiver in Go: Understanding the Difference with Parameters

When encountering method signatures like func (p *Page) save() error, one may wonder about the distinction between parameters and the receiver. This article clarifies this concept, explaining the role of the receiver in method declarations.

The receiver, denoted by (p *Page) in this example, is a unique parameter that every receiver method must have. Unlike regular parameters, it is declared before the method name and is not explicitly included in the parentheses of the method call. The receiver allows methods to access and manipulate the data associated with the type they are attached to.

The save() method described in the question takes a pointer to a Page struct as its receiver. This means that the method can operate on the specific instance of Page that was passed as the receiver. In contrast, regular parameters, if any, are passed to the method and can be used within its body.

To differentiate further, consider the following alternative signature:

func save(p *Page) error

This would result in a function instead of a method. It behaves differently since it receives a pointer to a Page instance as a parameter and does not have inherent access to the receiver's data or methods.

It's noteworthy that the receiver is essentially a syntactic sugar mechanism. One can achieve the same effect by manually calling the method:

(*Page).save(p)

Here, *Page refers to the type, and p is the receiver instance.

In summary, the receiver in Go is a special parameter that provides methods access to the data and functionality of the type they are attached to. While they resemble parameters, receivers are unique and serve a specific purpose in method declarations.

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