Class, constructor and inherance.

[Rikki Cattermole via Digitalmars-d-learn]

On 15/10/15 8:15 AM, holo wrote:
>>>>>
>>>>> I want to ask you for  advises what i could do with that class to make
>>>>> it looks more "pro"/elegant/build in "proper way". Probably there are
>>>>> lot of mistakes which all beginners are doing.
>>>>>
>>>>> eg.: Did i use interface correctly?
>>>>
>>>> You are reasonably close:
>>>> credential sig = new sigv4();
>>>
>>> Why are you creating sigv4 object with type credential? How in your
>>> opinion should look interface for such class?
>>>
>>>>
>>>> Although go is not really doing what I expect it to do.
>>>> To me go should be dedicated to performing a request given what ever
>>>> you need for just that request. The class sigv4 is your global state
>>>> aka what doesn't change per request.
>>>> To me what go returns is whatever is the common denominator for what
>>>> you need from it is.
>>>
>>> Not sure if i correctly understood that. Do you propose to take out eg
>>> signing process from go function and let it only to make requests?
>>> Signature is depending on kind of request and accurate time when request
>>> is send. That is why i all that things put to it.
>>
>> The implementation such as sigv4 can be configured with as much detail
>> as possible extra that you need.
>> The method go can for instance do what ever it needs to, to for fill
>> it's goal.
>>
>>>>
>>>> From what I can see, you probably want go to take the payload as an
>>>> argument.
>>>> That way you can reuse an instance of sigv4. Which is the ultimate
>>>> goal.
>>>
>>> In plan i wanted to change variables per request that why i left that
>>> public variables and created that arguments for constructor - to have
>>> possibility to change that  values durring creation of object.
>>>
>>> On example, im expecting it will be behaving like that:
>>>
>>> sigv4 obj = new sigv4();
>>> content =  obj.go();    //will get instances list
>>> obj.request_parameters = "Action=DescribeRegions&Version=2013-10-15"
>>> content2 = obj.go();    //will get list  of regions
>>> destroy(obj);
>>>
>>> so that go will get me back what i need per request not per one object
>>> live, or it wont work like that?
>>
>> It indeed should not.
>> Also remember go is currently returning an integer. Not data from the
>> request.
>
> I test it with such code:
>
> void main()
> {
>      SigV4 sig = new SigV4();
>      writeln(sig.go);
>      sig.requestParameters = "Action=DescribeRegions&Version=2013-10-15";
>          writeln(sig.go());
> }
>
> Actually it is working, first it returned to me default request
> DescribeInstances and right after that request DescirbeRegions. I
> understand that, before i will start parsing it with xml lib i need to
> convert it to string. Should it be solved in other way?
>
>>
>>> go method returns xml form (need to find out how force AWS to return
>>> JSON cos i saw xml module in dlang is deprecated) with structures
>>> depends on query - in default query that will be list of instances with
>>> all  parameters. That xml file i want to parse in higher
>>> classes/functions (different class for different request).
>>
>> If you need to use std.xml use it. We don't appear to be replacing it
>> any time soon.
>>
>> So here is the thing. You are tieing your usage of the API to SigV4
>> standard. This is bad bad bad. Any updates or changes to it, will
>> cause problems. If you want to tie yourself to said standard, then you
>> don't need OOP.
>
> How it could be solved in that case to not be tied to SigV4? If there
> will came some other request signing process it will need to be
> implement in that "go" function. Is there possibility to make it
> universal for all kind of signing processes? How it should be done in
> OOP (some example, pseudo code)? Or i missed what you are pointing to?
>
>>
>> Another thing, you may want to consider to use an interface as the
>> return type of go. That way your implementation of it can have extra
>> fields/methods which if you know that it is sigv4 you can cast to, to
>> get access to, should you need it.
>
> It interesting what you wrote. Can you show me some example (pseudo
> code) how it can be implemented and how it could be used? It think that
> it is what you wrote in previous post:
>
> Credential sigv4 = new sigv4();
>
> Remember im really beginner and some obvious things are not necessarily
> such for me. :)
>
>
>> Also classes start with a capital letter, like Credential or SigV4.
>> And D prefers camal casing aka requestParameters for variables/functions.
>
> Updated my code according to those directions.
>
> //holo

Just some ideas:

interface RequestResult {
	...
}

RequestResult go(string[string] requestParameters)