Blog / Go Language Spec

Third rule of selectors

October 26, 2023

Selectors

…

  1. As an exception, if the type of x is a defined pointer type and (*x).f is a valid selector expression denoting a field (but not a method), x.f is shorthand for (*x).f.

I find this wording to be confusing. That probably means some of you do, too. So here goes my best attempt at explaining it.

“if the type of x is a defined pointer type” refers to something like this:

type Person struct { // Person is a defined type
  Name string
}

var x = &Person{} // x is of type *Person, not Person, thus it is a "defined pointer type"

Since x is a pointer, the complete, canonical way to access the Name field on x as defined above would be:

name := (*x).Name

That is to say, we have to dereference x to get at its pointed-to value. That’s what (*x) does. Then we can access the field.

What the spec is telling us is that as a shorthand for this, we can use x in place of (*x):

name := x.Name

Quotes from The Go Programming Language Specification Version of August 2, 2023

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Illegal selectors

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