Class, constructor and inherance.
holo via Digitalmars-d-learn
digitalmars-d-learn at puremagic.com
Mon Oct 12 21:17:40 PDT 2015
On Tuesday, 13 October 2015 at 02:03:46 UTC, Rikki Cattermole
wrote:
> On 13/10/15 5:56 AM, holo wrote:
>> @Rikki:
>>
>>> If you didn't need to make it easily changeable I would say
>>> not even
>>> bother with OOP at all.
>>
>> Basically that what i had was enough for me and on top of that
>> i could
>> build my app. It need to just periodically check for new
>> instances and
>> if they are started or stopped and count "up and running time"
>> for
>> billing purpose. But like i said i want to learn programming
>> in D and
>> basically OOP too so i want to make it "proper way".
>>
>> BTW: i think right now i understand what tuple is, but still
>> don't know
>> for what to duplicate struct functionalities :). Those
>> Templates still
>> don't understand but i hope that will came naturally with time
>> and
>> practice. eg.. they are very similar to normal functions but
>> you can
>> call it with types not only attributes.. strange ;)
>>
>> I red yours advises and try to create according to it my own
>> first class.
>>
>> I moved time functions and variables to method "go" they need
>> to be
>> current as possible when im sending request, if wont
>> authorization could
>> not pass.. so i think they shouldn't be in constructor.
>>
>> I moved some other variables too, and created interface.
>>
>> From all that things came out such monster which is working
>> and doing
>> its job :)
>>
>> module sigawsv4;
>>
>> import std.stdio, std.process;
>> import std.digest.sha, std.digest.hmac;
>> import std.string;
>> import std.conv;
>> import std.datetime;
>> import std.net.curl;
>>
>> interface credential
>> {
>> int go();
>> }
>>
>> class sigv4 : credential
>> {
>> //could be changed to take some structure as parameter
>> instead of
>> such ammount of attributes
>>
>> this(string methodStr = "GET", string serviceStr = "ec2",
>> string
>> hostStr = "ec2.amazonaws.com", string regionStr = "us-east-1",
>> string
>> endpointStr = "https://ec2.amazonaws.com", string payloadStr =
>> "",
>> string parmStr = "Action=DescribeInstances&Version=2013-10-15")
>> {
>>
>> this.method = methodStr;
>> this.service = serviceStr;
>> this.host = hostStr;
>> this.region = regionStr;
>> this.endpoint = endpointStr;
>> this.payload = payloadStr;
>> this.request_parameters = parmStr;
>>
>> this.accessKey = environment.get("AWS_ACCESS_KEY");
>> this.secretKey = environment.get("AWS_SECRET_KEY");
>> }
>>
>> public:
>> string method;
>> string service;
>> string host;
>> string region;
>> string endpoint;
>> string payload;
>> string request_parameters;
>>
>>
>> int go()
>> {
>> //time need to be set when we are sending request
>> not before
>> auto currentClock = Clock.currTime(UTC());
>> auto currentDate = cast(Date)currentClock;
>> auto curDateStr = currentDate.toISOString;
>> auto currentTime = cast(TimeOfDay)currentClock;
>> auto curTimeStr = currentTime.toISOString;
>> auto xamztime = curDateStr ~ "T" ~ curTimeStr ~
>> "Z";
>>
>> canonicalURI = "/";
>> canonicalQueryString = request_parameters;
>> canonicalHeadersString = "host:" ~ this.host ~
>> "\n" ~
>> "x-amz-date:" ~ xamztime ~ "\n";
>> signedHeaders = "host;x-amz-date";
>>
>> auto canonicalRequest =
>> getCanonicalRequest(canonicalURI,
>> canonicalQueryString, canonicalHeadersString, signedHeaders);
>>
>> string credentialScope = curDateStr ~ "/" ~
>> region ~ "/" ~
>> service ~ "/" ~ "aws4_request";
>>
>> string stringToSign = algorithm ~ "\n" ~ xamztime
>> ~ "\n" ~
>> credentialScope ~ "\n" ~
>> sha256Of(canonicalRequest).toHexString.toLower;
>>
>> auto signingKey = getSignatureKey(secretKey,
>> curDateStr,
>> region, service);
>>
>> string signature =
>> hmac!SHA256(stringToSign.representation,
>> signingKey).toHexString.toLower;
>>
>> string authorizationHeader = algorithm ~ " " ~
>> "Credential=" ~ accessKey ~ "/" ~ credentialScope ~ ", " ~
>> "SignedHeaders=" ~ signedHeaders ~ ", " ~ "Signature=" ~
>> signature;
>>
>>
>> auto client = HTTP(endpoint ~ "?" ~
>> canonicalQueryString);
>> client.method = HTTP.Method.get;
>> client.addRequestHeader("x-amz-date", xamztime);
>> client.addRequestHeader("Authorization",
>> authorizationHeader);
>> auto content = client.perform();
>>
>> return content;
>> }
>>
>> private:
>> const algorithm = "AWS4-HMAC-SHA256";
>>
>> string accessKey;
>> string secretKey;
>>
>> string currentClock;
>> string currentDate;
>> string curDateStr;
>> string currentTime;
>> string curTimeStr;
>> string xamztime;
>>
>> string canonicalURI;
>> string canonicalQueryString;
>> string canonicalHeadersString;
>> string signedHeaders;
>>
>>
>>
>> alias sign = hmac!SHA256;
>>
>> auto getSignatureKey(string key, string dateStamp,
>> string
>> regionName, string serviceName)
>> {
>> auto kString = ("AWS4" ~ key).representation;
>> auto kDate = sign(dateStamp.representation,
>> kString);
>> auto kRegion = sign(regionName.representation,
>> kDate);
>> auto kService = sign(serviceName.representation,
>> kRegion);
>> auto kSigning =
>> sign("aws4_request".representation, kService);
>>
>> return kSigning;
>> }
>>
>>
>> auto getCanonicalRequest(string canonicalURI, string
>> canonicalQueryString, string canonicalHeadersString, string
>> signedHeaders)
>> {
>> string payloadHash =
>> sha256Of(payload).toHexString.toLower;
>> string canonicalRequest = method ~ "\n" ~
>> canonicalURI ~
>> "\n" ~ canonicalQueryString ~ "\n" ~ canonicalHeadersString ~
>> "\n" ~
>> signedHeaders ~ "\n" ~ payloadHash;
>> return canonicalRequest;
>> }
>> }
>>
>> void main()
>> {
>> sigv4 sig = new sigv4();
>> writeln(sig.go());
>> }
>>
>> 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.
>
> 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?
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).
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