Can Pointer Methods Be Called on Non-Pointer Types in Go?

Pointer Methods on Non-Pointer Types: Unraveling the Confusion

Despite the notion that pointer methods can only be invoked on pointers, it is possible to execute them on non-pointer values. This apparent discrepancy requires clarification.

The Rule of Receivers

The principle states that value methods can be called both on values and pointers, while pointer methods are restricted to pointers only.

The Case in Point

In the given example, the car.fourWheels() method has a pointer receiver. However, we can invoke it on a car value using the expression c.fourWheels().

The Truth Unveiled

This is possible because Go's specification allows calling a pointer method on a non-pointer value if the latter is addressable. In the example, the car variable is addressable, so it can be converted into a pointer using the & operator. The expression c.fourWheels() is, therefore, equivalent to the shorthand:

(&c).fourWheels()

Clarifying the Rule

The "receiver rule" should be interpreted as follows:

• Value methods can always be called on values or pointers.
• Pointer methods can be called on pointers, and in some cases on values that are addressable.

Non-Addressable Expressions

However, it is important to note that not all expressions result in addressable values. For example, function return values and map indexing expressions typically yield non-addressable values. In such cases, pointer methods cannot be directly invoked on those expressions' results.

Conclusion

Calling pointer methods on non-pointer values is possible due to Go's addressability rule. This allows us to leverage pointer methods in a more flexible manner, but it is essential to be aware of the limitations imposed by non-addressable expressions.

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