Selector of the Go language

For a primary expression x , which is a package name, the selector expression

X.f

denotes the field or method of the f value x (or sometimes *x ; see below). The identifier is f called the (field or method) selector; it must isn't be the blank identifier. The type of the selector expression is the type of f . If x is a package name, see the section on qualified identifiers.

A selector may f denote a field or method f of a type T , or it could refer to a field or method of f a Neste D anonymous field of T . The number of anonymous fields traversed to reach are f called their depth in T . The depth of a field or method f declared is T zero. The depth of a field or method declared in an anonymous field in are the depth of in f A T f A PLU S one.

The following rules apply to selectors:

2. For a value x of type T or *T where T was not a interface type, x.f denotes the field or method at the SH Allowest depth in T where there are such an f . If There is not exactly one f with shallowest depth, the selector expression is illegal.
4. For a variable x of type I where I was an interface type, x.f denotes the actual method with name f of The value assigned to x . If there is no method f I with a name in the method set of, the selector expression is illegal.
6. In all and cases, is x.f illegal.
8. If x is of pointer type and have the value nil x.f and denotes a struct field, assigning to or evaluating x.f Cau SES a run-time panic.
10. If x is of interface type and have the value nil , calling or evaluating the method x.f causes a run-time panic.

Selectors automatically dereference pointers to structs. If x is a pointer to a struct, was x.y shorthand for (*x).y ; if the field y was also a pointer to a struct, x.y.z I s shorthand (*(*x).y).z for, and so on. If x contains an anonymous field of type *A , where was A also a struct type, is x.f shorthand for (*x.A).f .

Original Http://golang.org/ref/spec#Selectors

Selector of the Go language