在c++中“[这]”是什么意思?

When I was reading the Cocos2dx 3.0 API, I found something like this:

当我阅读Cocos2dx 3.0 API时，我发现了如下内容:

auto listener = [this](Event* event){
    auto keyboardEvent = static_cast<EventKeyboard*>(event);
    if (keyboardEvent->_isPressed)
    {
        if (onKeyPressed != nullptr)
            onKeyPressed(keyboardEvent->_keyCode, event);
    }
    else
    {
        if (onKeyReleased != nullptr)
            onKeyReleased(keyboardEvent->_keyCode, event);
    }
};

What does [this] mean? Is this new syntax in C++11?

(这)是什么意思?这是c++ 11中的新语法吗?

1 个解决方案

#1

What does [this] means?

[这]意味着什么?

It introduces a lambda - a callable function object. Putting this in the brackets means that the lambda captures this, so that members of this object are available within it. Lambdas can also capture local variables, by value or reference, as described in the linked page.

它引入一个lambda -一个可调用的函数对象。把它放在括号中意味着lambda捕获到这个对象，因此该对象的成员可以在其中使用。Lambdas还可以根据值或引用捕获局部变量，如在链接页面中描述的那样。

The lambda has an overload of operator(), so that it can be called like a function:

lambda具有操作符()的重载，因此可以像函数一样调用:

Event * event = some_event();
listener(event);

which will run the code defined in the body of the lambda.

它将运行lambda中定义的代码。

Is this new syntax in C++11?

这是c++ 11中的新语法吗?

Yes.

是的。

#1