QPushButton's shortcut not work when the text change

[SGaist]

That's the correct behavior following the text property

[ljc123456gogo]

@SGaist
Oh! I see:

Any previous shortcut will be overwritten or cleared if no shortcut is defined by the text.

This property is really easy to make puzzle.
Maybe I should reset the shortcut after the text change.
Thanks.

[SGaist]

If you want to keep the same shortcut then yes.

[ValentinMichelet]

@ljc123456gogo said:

2. I know it will use copy construct, but the argument is temp variable , so I can't use reference.

I don't get it. Did you assume that the compiler would complain, or did you actually get a compilation error with a const& variable? In fact I'm not sure to understand what you mean by "temp variable".

class A {
public:
  void methodA(QString const& p_string) {
    /* do stuff with p_string, even assign it to a private member... */
  }
};

int main(int argc, char *argv[])
{
  A a;
  QString qstr("My string");
  a.methodA(qstr);

  return 0;
}

This works perfectly fine, and I think that qstr is a temp variable, right?

Anyway, I didn't know that calling setText() would remove the previous shortcut. This is so unintuitive. Does anyone know the reason behind this strange behavior?

[ljc123456gogo]

@ValentinMichelet
I said temp variable that means like:

int main(int argc, char *argv[])
{
  A a;
  a.methodA(QString("My string")); //When the fuction call end, this QString was "dead", it's memory maybe change by other pragram

  return 0;
}

And when the QString getout of it's scope, it also will "dead". It belong C++ knowledge.
Your code run normally because the QString until the pragram end it still exist, it is not what I mean.

[ValentinMichelet]

I still don't get it, sorry.

#include <QDebug>

class A {
public:
  void setString(QString const& p_string) {
    m_string = p_string;
  }
  QString m_string;
};

int main(int argc, char *argv[])
{
  A a;
  a.setString(QString("My string"));
  qDebug() << a.m_string;

  return 0;
}

This works like a charm.

[ljc123456gogo]

@ValentinMichelet
I say: it's memory maybe changed by other pragram later. Not immediate be changed. It would not have complie error. If you want to see error, you can let it wait some minutes and see it's data, it maybe changed.

[ljc123456gogo]

@ValentinMichelet
you also can see http://stackoverflow.com/questions/10540157/c-temporary-variable-lifetime

[ValentinMichelet]

@ljc123456gogo said:

@ValentinMichelet
you also can see http://stackoverflow.com/questions/10540157/c-temporary-variable-lifetime

This is a completely different issue. First, the reference is constant in my code, not in your link. Then, it's a parameter, not something you create inside your constructor.
The code I provided is a classic way to call a method with some parameters that you won't modify (read only) which insures that no copy will be done. There won't be any issue if you simply read it. It won't be overwritten when you are inside of your constructor. This is C++ knowledge.

Two problems can occur tho:

1. You const_cast it and modify it, but whatever happens, you deserve it.
2. You store the address of the temp, leading to a potential segfault.

Other than that, there is nothing wrong. In fact, it's a good practice to pass a const ref in a method/constructor as long as you do not have to modify it inside your method/constructor.

[ljc123456gogo]

@ValentinMichelet
Okay, I make some misunderstand, I overlook the "const" in your codes before. If doesn't have const, it's danger.
I should use const reference.

[ValentinMichelet]

@ljc123456gogo
I'm glad we both agree on that =)