On Mon, Jan 1, 2018 at 10:21 PM, Ian Lance Taylor <i...@golang.org> wrote:
> On Mon, Jan 1, 2018 at 6:46 PM, Tong Sun <suntong...@gmail.com> wrote: > > > > I think I generally understand how embedding > > (https://golang.org/doc/effective_go.html#embedding) works in GO. > > However, when it comes to the following problem, I'm at lost again. > > > > I'm trying to extend the `html.Tokenizer` with new methods of my own: > > > > type MyTokenizer struct { > > html.Tokenizer > > } > > > > > > func NewMyTokenizer(i io.Reader) *MyTokenizer { > > z := html.NewTokenizer(i) > > return *MyTokenizer(z) > > return &MyTokenizer{z} > > } > > > > > > > > so code like > > > > z := html.NewTokenizer(body) > > ... > > func parseBody(z *html.Tokenizer) { > > tt := z.Next() > > ... > > testt := z.Token() > > ... > > > > > > can become: > > > > z := NewMyTokenizer(body) > > ... > > func (z *MyTokenizer) parseBody() { > > tt := z.Next() > > ... > > > > testt := z.Token() > > ... > > > > > > > > > > However, I'm really struggling to make it work as I was expected. > > > > Somebody help please, what's the proper way to extend a type with new > > methods of my own, while still able to access all existing methods? > > The best way to get help for this is to show us precisely what you > did, ideally in a small complete, stand-alone, example, The *small complete, stand-alone, example *has been provided in OP as https://github.com/suntong/lang/blob/master/lang/Go/src/xml/htmlParserTokens.go and tell us > what you expected to happen, and tell us precisely what happened > instead. *What expected to happen*: adding the following would work: type MyTokenizer struct { html.Tokenizer } func NewMyTokenizer(i io.Reader) *MyTokenizer { z := html.NewTokenizer(i) return *MyTokenizer(z) return &MyTokenizer{z} } > In this case I don't know what to suggest because you didn't > say what you expect and you didn't say what happened. > Can't make it work. The return *MyTokenizer(z) return &MyTokenizer{z} Are just the last two attempts that I make, apart from many other failed attempts that I've lost track of, but *neither compiles*. > Further more, how to extend the above even further? -- > > > > - I plan to define an interface with a new method `WalkBody()`, in which > a > > "virtual" method of `VisitToken()` is used. > > - Then I plan to define two different type of MyTokenizer, with their own > > `VisitToken()` methods, so the same `WalkBody()` method defined in > > MyTokenizer will behave differently for those two different types. > > > > How to architect above in Go? > > First, think in Go terms, don't think in terms like "virtual method" > that do not exist in Go. > > What you want is something like > > type TokenVisitor interface { > VisitToken() > } > > Then your WalkBody function will take a TokenVisitor, and your > different types will implement different VisitToken methods. > > (I see that you said WalkBody method, but you probably want a WalkBody > function instead.) > I did meant WalkBody method. See: https://github.com/suntong/lang/blob/master/lang/Go/src/xml/htmlParserTokens.go#L54 -- You received this message because you are subscribed to the Google Groups "golang-nuts" group. To unsubscribe from this group and stop receiving emails from it, send an email to golang-nuts+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
