[go-nuts] easy way to create and traverse two-dimension container/list in golnag

On Friday, September 27, 2013 1:27:43 PM UTC+8, Steven Blenkinsop wrote:


That's called a type assertion. It lets you unwrap the value inside an
interface by saying what type it has. If you're wrong, your program fails
at runtime. You can use the comma-ok notation to get a boolean indicating
whether you were right or not rather than failing: `v, ok :=
e.Value.(*list.List)`. A type assertion doesn't let you change the type of
the value in the interface; the type you assert it to be has to be
identical to the type of the value that was put into the interface. The
exception is that you can assert that the value in an interface also
implements another interface, giving you a value of the second interface
type, or failing at runtime if you're wrong (which you can still avoid by
using the comma-ok notation).

Conversions are for when the compiler knows you can turn a value of one
type into a value of another type, so it fails at compile time if you're
wrong, rather than at runtime.