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, <matthewju...@gmail.com> 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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