the difference between type and type address in struct

[Mandel]

the difference between type  and  type address in struct

type dog struct {

 age int 

 name string

} 

type A struct {

     d *dog

}

type B struct {

     d dog

}

the difference between struct A and struct B.

[jake...@gmail.com]

The terminology we would generally use is '*dog' is a pointer, not a "type address".

The difference really has nothing to do with structs, but is the difference between a value and a pointer to a value. If you understand pointers in general, then this more complicated case will make sense. I suggest searching "pointers in go explained", which will give you a number of tutorials that explain pointers.

In this case, the biggest difference is that each instance of B will always contain its own 'dog' value, but instances of A may share a 'dog' value, if d points to the same 'dog' value. Seehttps://go.dev/play/p/NlSsMc8b7To for a demonstration.

[Brian Candler]

Another difference is that the *dog value in type A may be nil, meaning "no dog" - indeed, this is the default (zero) value of a pointer.

Attempting to follow (deference) such a nil pointer, in other words trying to access the dog value that it points to, will result in a panic.