在Qt中从静态类方法发送信号 [英] Sending signal from static class method in Qt

问题描述

我试图编写一个静态回调函数，该函数从同一类中的另一个静态函数频繁调用。我的回调函数需要 emit 一个信号，但由于某种原因，它只是没有这样做。我把它放在一个调试器和插槽从来没有被调用。然而，当我放置代码我用来 emit 在非静态函数中的数据，它的工作原理。有没有原因，我不能从静态函数发出信号？我尝试声明一个类的新实例，并调用emit函数，但没有运气。

I am trying to code a static callback function that is called frequently from another static function within the same class. My callback function needs to emit a signal but for some reason it simply fails to do so. I have put it under a debugger and the slot never gets called. However when I place the code I used to emit the data in a non-static function it works. Is there a reason I cannot emit a signal from a static function? I have tried declaring a new instance of the class and calling the emit function but with no luck.

class Foo
{
signals:
    emitFunction(int);
private:
    static int callback(int val)
    {
        /* Called multiple times (100+) */
        Foo *foo = new Foo;
        foo.emitFunction(val);
    }
    void run()
    {
        callback(percentdownloaded);
    }
};

我已经发布了一些基本的代码，演示了我试图做什么。我将根据请求过帐全部代码。

I have posted some basic code that demonstrates what I am attempting to do. I will post full code upon request.

编辑：我发布完整的代码，因为这是一个奇怪的情况。 http://pastebin.com/6J2D2hnM

I am posting the full code since this is kind of an odd scenario. http://pastebin.com/6J2D2hnM

推荐答案

这不会工作，因为你创建一个新的Foo每次你输入静态函数，并且你不连接到一个插槽的信号。

That is not going to work, because you are creating a new Foo every time you enter that static function, and you do not connect a signal to a slot.

所以，修复是将对象传递给该函数：

So, the fix would be to pass the object to that function :

class Foo
{
signals:
    emitFunction(int);
private:
    static int callback(int val, Foo &foo)
    {
        /* Called multiple times (100+) */
        foo.emitFunction(val);
    }
    void run()
    {
        callback(percentdownloaded, *this);
    }
};

另一个选择是使用 postEvent ，但我不推荐。

Another option is to use postEvent, but I wouldn't recommend it.

由于您不能修改回调的签名，您可以这样做：

Since you can not modify callback's signature, you can do it like this :

class Foo
{
signals:
    emitFunction(int);
private:
    static int callback(int val)
    {
        /* Called multiple times (100+) */
        theFoo->emitFunction(val);
    }
    static Foo *theFoo;
    void run()
    {
        callback(percentdownloaded, *this);
    }
};

但您必须在某处初始化该静态变量。

but you'll have to initialize that static variable somewhere.

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