问题描述

我正在尝试编写一个静态回调函数，该函数经常从同一类中的另一个静态函数调用.我的回调函数需要 emit 一个信号，但由于某种原因它根本无法这样做.我把它放在调试器下，slot 永远不会被调用.但是，当我将用于 emit 数据的代码放置在非静态函数中时，它可以工作.有什么原因我不能从静态函数发出信号吗?我曾尝试声明该类的一个新实例并调用发射函数，但没有成功.

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代码来演示我正在尝试做什么.我会根据要求发布完整的代码.

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

我发布了完整的代码，因为这是一个奇怪的场景.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

那是行不通的，因为您每次进入该静态函数时都会创建一个新的 Foo，并且您没有将信号连接到插槽.

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.

因此，修复方法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);
    }
};

另一种选择是使用 postEvent，但我不会不推荐.

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

既然你不能修改回调的签名，你可以这样做:

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);
    }
};

但是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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