CReason

This class is necessary to link two CThing instances to give the link an explaination. This enables us to link the same CThing’s multiple time.

• thing1 - reason - thing2

For example:

• Heinz - wrote - ‘Trees of Estonia’
• Heinz - signed - ‘Trees of Estonia’

Links are unidirectional. Meaning if it’s true that

• Heinz - wrote - ‘Trees of Estonia’

it may not be true that

• ‘Trees of Estonia’ - wrote - Heinz

But to ensure thing2 feels the link, it will be informed that a link to it became established. The linked thing registers which thing is linking to it only ones. In our example ‘Trees of Estonia’ registers, that Heinz links to it.

If some process/entity needs to know how often and for which reasons, it has to go to Heinz and ask. The linking thing is resonsible for correct management of links, reasons and backlinks.

CReason registers each link it is used for

Demostration

#include <iostream>

#include "odb.h"
#include "thing.h"

int main()
    {
    // generating the objects
    auto oOdb    = odb::COdb();
    auto pThing1 = oOdb.MakeThing("Ulrich");
    auto pThing2 = oOdb.MakeThing("Fred");
    auto pReason = oOdb.MakeReason("pays");
    // create a connection
    pThing1->Link(pThing2, pReason);
    // let them explain the situation
    std::cout << "thing: " << *pThing1 << '\n';
    std::cout << "thing: " << *pThing2 << '\n';
    }

Output:

thing: Ulrich
   => linked to: "Fred" for reason: "pays" = Ulrich pays Fred
thing: Fred
   <= linked from: Ulrich

class odb::CReason

A Reason to link two Things (Unidirectional)

Inherits from Identifiable< CReason >

Public Functions

CReason()

Forbidden.

CReason(CReason const&)

There is no reason to copy a CReason.

CReason(CReason&&)

make_shared<T> moveconstruct

CReason(std::string const &crsName)

Normal constructor, receiving the name of the reason.

CReason(size_t nId, std::string const &crsName)

Load constructor, receiving the ID and name of the reason.

operator std::string const&()

Conversion operator will return the name of the instance.

void RelationAdd(PThing &poThingFrom, PThing &poThingTo)

Add the information about a link from one CThing to another regarding ‘this’ reason.

void RelationSub(PThing &poThingFrom, PThing &poThingTo)

Removes a link between two CThing’s.

Removes the information about a particular link from one CThing to another regarding ‘this’ reason

Parameters

• poThingFrom: The thing the link is claimed to be made from
• poThingTo: The thing the link is claimed to be made to

void print()

Prints an informational output to std::cout.

Public Static Attributes

constexpr auto s_csNameUnnamedReason = {"unnamedReason"}

The name of an unnamed reason.

Protected Attributes

std::multimap<PThing, PThing> m_mRelations

A map containing links from one thing to another.

Friends

std::ostream &operator<<(std::ostream &ros, CReason const &croReason)

Output operator to do an output of the instance.