The code:
type ByteSlice []byte
func (p *ByteSlice) Append(data []byte) {
slice := *p
slice = append(slice, data...)
*p = slice
}
func main() {
x := ByteSlice{1, 2, 3}
y := []byte{4, 5}
x.Append(y)
fmt.Println(x)
}
Ok, I understand why and how pointer works, but I've always wondered why we use * operator to pass pointer to function.
*ptr is to deference the ptr and return the value saved in the pointer ptr.&var returns the address of the variable var.Why we do not use &ByteSlice to pass pointer to function?
I am confused. Isn't this function passing pointer?
According to Go spec (http://golang.org/ref/spec#Pointer_types)
PointerType = "*" BaseType .
BaseType = Type .
This also confuses me. Why we use star(*) operator both to get the pointer of variable and dereference pointer? Looks like we don't use & for this case both in C and Go...
The * in func (p *ByteSlice) Append(data []byte) { is simply declaring that p is of type *ByteSlice.
The passing of a pointer takes place here:
x.Append(y)
As the Specification says (my emphasis):
A method call x.m() is valid if the method set of (the type of) x contains m and the argument list can be assigned to the parameter list of m. If x is addressable and &x's method set contains m, x.m() is shorthand for (&x).m():
In your case, x.Append(y) is a shorthand for (&x).Append(y). There you have your &-sign.