On 15-4-2015 21:05, Keith Gardner wrote:
> QPropertyGuard g{this};
> g.addProperty("a"); // use QObject::property
> g.addProperty("b", m_b); // take value member by reference
> g.addProperty(m_c, &cChanged); // ...and also slot address
There's type erasure going on, so it will allocate memory.
Allocating memory
in a setter that might just change an int is what I call inefficient.
Would something like this be better?
// constructor
// Provide an initial value and a std::function to notify about the change
Property<bool> m_example = Property<bool>(false, [&](bool value){
emit exampleChanged(value);
});
// getter
bool *::example() const {
return m_example;
}
// setter
void *::setExample(bool value) {
m_example = value;
}
The working code for this example can be found
https://github.com/kreios4004/Property_Class.
Thank you for posting that.
I took a look at it, but I am not sure it actually solves much. It moves
the check if something changed to the wrapped variable, but it makes
using that value then more complicated. Instead of using the variable
directly, one now has to go through m_example.getValue() everywhere. Not
pretty, I think. The case of modifying more than one property in one go
is also not solved. On the one hand, dependent properties (such a
isValid property) are not updated unless you manually write that code
again, and on the other hand if you use this to set more than one
property in a method, you still are sending signals at the point the
class is in an inconsistent state.
One nice side effect of my implementation is that the notification is
actually only send once. Even if the property value is changed multiple
times in the meantime, you still get only one notification. That can be
very convenient, even if you don't use it much.
André
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