CODEWITHSUNDEEP
c++qtsignals-slots
Umesha MS
Umesha MS

Reputation: 2921

Updating pointer using signals and slots

I am very new to Qt; please help me to solve the problem.

I am using a thread to perform intensive operations in the background. Meanwhile I want to update the UI, so I am using SIGNALS and SLOTS. To update UI I emit a signal and update UI.

Let us consider below sample code,

struct sample
{
    QString name;
    QString address;
};

void Update(sample *);

void sampleFunction()
{
    sample a;
    a.name = "Sachin Tendulkar";
    a.address = "India"
    emit Update(&a);
}

In the above code we are creating a local object and passing the address of a local object. In the Qt document, it says that when we emit a signal it will be placed in the queue and late it will be delivered to the windows. Since my object is in local scope it will be delete once it goes out of the scope.

Is there a way to send a pointer in a signal?

Upvotes: 2

Views: 2841

Answers (2)

Josh Knauer
Josh Knauer

Reputation: 1754

Unless you've determined that this code is a performance bottleneck you would be better to just pass a copy of the object rather than a pointer.

Really, I mean it.

However, if you must use pointers then use a boost::shared_ptr and it will delete itself. 

void Update(boost::shared_ptr<sample> s);

void sampleFunction()
{
    boost::shared_ptr<sample> a = boost::shared_ptr<sample>(new sample());
    a->name = "Sachin Tendulkar";
    a->address = "India"
    emit Update(a);    
}

Upvotes: 4

MSalters
MSalters

Reputation: 179907

You're insisting on doing the wrong thing, why? Just send the Sample itself:

void Update(sample);
//...
sample a("MSalters", "the Netherlands");
emit Update(a);

Upvotes: 5

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