Put your methods on *MyTokenizer.
On Wednesday, 3 January 2018 14:52:41 UTC+11, Tong Sun wrote:
>
> I gave it a try, but unfortunately, it doesn't work for me.
>
> To begin with, this works,
>
> type MyTokenizer struct {
> *html.Tokenizer
> }
>
> func NewMyTokenizer(i io.Reader) *MyTokenizer {
> z := html.NewTokenizer(i)
> return &MyTokenizer{z}
> }
>
> However,
>
> On Tue, Jan 2, 2018 at 10:26 AM, <matthe...@gmail.com <javascript:>>
> wrote:
>
>> You want different tokenizer types to be used in the same WalkBody
>> implementation. Interfaces abstract the implementation from the calling
>> computation.
>>
>> I think Ian did answer your question.
>>
>> type TokenVisitor interface {
>> VisitToken()
>> }
>>
>> func WalkBody(of TokenVisitor) {
>> // here you call of.VisitToken()
>> }
>>
>> type MyTokenizer1 struct {
>> *html.Tokenizer
>> }
>>
>> func (the MyTokenizer1) VisitToken() {
>>
>> }
>>
>> type MyTokenizer2 struct {
>> *html.Tokenizer
>> }
>>
>> func (the MyTokenizer2) VisitToken() {
>>
>> }
>>
>> // call WalkBody somewhere with either MyTokenizer1 or MyTokenizer2
>>
>
>
> As soon as I tried above and turned
>
> type MyTokenizer struct
>
> to
>
> type TokenVisitor interface
>
> everything started to break down. Here is the code that I've put together
> so far:
>
>
> https://github.com/suntong/lang/blob/master/lang/Go/src/xml/htmlParserTokens2.go
>
> I got:
>
> ./htmlParserTokens2.go:82:10: z.Next undefined (type TokenVisitor has no
> field or method Next)
>
> So let me reiterate what I hope to achieve,
>
>
> 1. extend the `html.Tokenizer` with new methods of my own
> 2. while still able to access all existing html.Tokenizer methods in
> the mean time
> 3. define a function `WalkBody()` (or an interface method)
> 4. in which an interface method of `VisitToken()` is used, which will
> behave differently for different types
>
> The first two goals can be achieved by "type MyTokenizer struct", but as
> soon as I change that to the interface type to act as the base for the
> two different extended types, goal#2 breaks.
>
> So far this is only a small test example, in which
> only z.Next(), z.Err(), z.TagName() etc are currently used. But in real
> life I'll using all the html.Tokenizer methods, and published variables.
> I.e.,
>
> I'm not seeing the light at the end of the tunnel where all above 4 goal
> can be achieved together.
>
> Seem to me some compromise has to be made, what is the least compromise to
> make?
> Anybody can help please?
>
> Again, the code that I've put together so far is at:
>
>
> https://github.com/suntong/lang/blob/master/lang/Go/src/xml/htmlParserTokens2.go
>
> Thanks
>
>
> On Tuesday, January 2, 2018 at 8:45:56 AM UTC-6, Tong Sun wrote:
>>
>>>
>>>
>>> On Mon, Jan 1, 2018 at 9:46 PM, Tong Sun <sunto...@gmail.com> wrote:
>>>
>>>> Hi,
>>>>
>>>> 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?
>>>>
>>>
>>>
>>> Thanks to Jason Phillips' help, the above part is solved:
>>>
>>> type MyTokenizer struct {
>>> *html.Tokenizer
>>> }
>>>
>>> func NewMyTokenizer(i io.Reader) *MyTokenizer {
>>> z := html.NewTokenizer(i)
>>> return &MyTokenizer{z}
>>> }
>>>
>>> What's remaining is,
>>>
>>> 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?
>>>>
>>>
>>> I've found this afterward,
>>>
>>> http://hackthology.com/object-oriented-inheritance-in-go.html
>>>
>>> I'll digest and try it out, and see how that can solve the above
>>> problem, because it builds bottom up (not mid-way up).
>>>
>>> Meanwhile, if someone can explain how to think and solve such problem in
>>> Go, that'd be much appreciated. Only at the architectural level would be
>>> fine for me, I can try it out myself. The real problem to me is that I have
>>> a *systematic *thinking in OO how to solve such kind of inherit &
>>> enhance problem, and there is a *practical *implementation in place for
>>> me, the virtual functions. But when it comes to Go, I still need help for
>>> how to *think*, and how to *do*.
>>>
>>> Thanks!
>>>
>>>
>>>>
>>>> For your convenience, you can use this as an easy start, when
>>>> demonstrating your architectural solution.
>>>>
>>>> https://github.com/suntong/lang/blob/master/lang/Go/src/xml/htmlParserTokens.go
>>>>
>>>>
>>>> Thx a lot!
>>>>
>>>>
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>>>
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