Running a function depending upon multiple signals

Question

I have two signals which are NOT necessarily received at the same time.

First signal

First signal is emitted by MyClass and is handled by a slot of MyClass:

QObject::connect(this, &MyClass::ready, 
                 this, &MyClass::handleReady);

void MyClass::handleReady()
{
    qDebug() << "Ready to do next step";
}

// ... somewhere in MyClass implementation, signal is emitted:
emit ready();

Second signal

Second signal is emitted by a member object and is handled by a slot of MyClass:

QObject::connect(m_member, &MemberClass::enabledChanged, 
                 this,     &MyClass::handleEnabledChange);
//...
void MyClass::handleEnabledChange(const bool enabled)
{
    qDebug() << "Is member enabled?" << enabled;
}

I intend to run some code (like a function), depending upon two condition:

First signal, i.e. ready is received
Second signal, i.e. enabledChanged, is received and its Boolean parameter is true

I cannot figure out how to check for satisfaction of above conditions.

UPDATE

Now my signals count is increased to three. So my code execution depends on three conditions.

Are the signals always coming in this order or is the order irrelevant? — RoQuOTriX, Sep 18 '19 at 10:58

RoQuOTriX · Accepted Answer · 2019-09-18T11:07:40.560

Write a method in MyClass which checks if both conditions are true and call this methiod in both slots. Make the conditions member of myClass

bool MyClass::areBothConditionsTrue() {
    if(m_conditionA && m_conditionB)
        return true:
    return false;
}

void MyClass::handleReady()
{
    qDebug() << "Ready to do next step";
    m_conditionA = true;
    bool b = areBothConditionsTrue();
}

void MyClass::handleEnabledChange(const bool enabled)
{
    qDebug() << "Is member enabled?" << enabled;
    m_conditionB = enabled;
    bool b = areBothConditionsTrue();
}

The further code does depend on what you want to do with this information

Thanks =) let me try to implement this approach :) – Megidd Sep 18 '19 at 11:07 — Megidd, Sep 18 '19 at 11:07

score 2 · Answer 2 · answered Sep 18 '19 at 12:17

I do not have reputation enough to comment RoQuOTriX answer so made a separate one.

In case your handlers count will increase, you can create the state object in MyClass which stores all conditions by adding extra level of abstraction:

void MyClass::handleReady(State& state)
{
    qDebug() << "Ready to do next step";
    state.m_conditionA.setFlag(true);
}

...but then you will need to implement the State class and State's conditions holder class inherited from QObject to emit signal flagChanged when setFlag is called. Then just connect(m_conditionA, &Condition::flagChanged, this, &State::checkAllConditions) and store all conditions in some associative container.

Actually my handlers count is increased to 3 now! Thanks =) – Megidd Sep 18 '19 at 12:25 — Megidd, Sep 18 '19 at 12:25

Running a function depending upon multiple signals

First signal

Second signal

UPDATE

2 Answers2