Method Set
A method set is the Golang feature where the compiler knows the set of the methods available for a type and this set is created based on the method receiver type.
Since a method receiver can be both a value or a pointer, the compiler decides the method set based on the variable type.
In case of regular methods, a T or T type can call a methods with T orT receiver. There is no restriction.
The restriction of T variable not being able to call methods of *T receiver applies only to interfaces.
Worry about method sets only when working with interfaces.
From Golang FAQ
This distinction arises because if an interface value contains a pointer *T, a method call can obtain a value by de-referencing the pointer, but if an interface value contains a value T, there is no safe way for a method call to obtain a pointer. Doing so would allow a method to modify the contents of the value inside the interface, which isn't permitted by the language specification.
Selector
A selector is the . operator which is used to call the method or access the field.
When the dot operator is used on a type, the compiler knows which methods are available for the type based on the method set.
Method Sets of interface
- Value receivers operate on the copies of the original value. So this can be called using a T or *T. This is because, if T is known then the compiler automatically gets the address (using &) to call the method.
- Pointer receivers can be called only using pointer types. So only type an interface type *T can call.
In all programming languages, we must understand the difference between a function and a method. All methods are functions. But not functions are methods.
A method is a function that's linked with the context of a type/struct/class.
Understanding Method Sets in Go (semanticreatures.com)
A detailed explanation of how method sets work in Go, including practical examples and diagrams.
Pointer vs Value Methods in Go (gronskiy.com)
A comparison of pointer and value receivers in Go, with code samples and best practices.