从函数返回对象的引用，并修改std :: list中的（原始）对象 [英] Return a reference to object from function, and modify the (original) object which is in a std::list

问题描述

我不习惯C ++。我试图找到（通过函数），然后操作std :: list中对象内的值



有人可以帮忙吗？谢谢。

I'm not used to C++. I'm trying to find (via a function), then manipulate values inside an object that is in a std::list

Can anybody help? Thanks.

MyObject getObjectByMyValue(MyValue value)
{
	for (MyObject object : _objects)
        {
		if (object.value == value)
		{
			return object;
		}
	}
	throw("");
}

void otherFunction()
{
	try
	{
		MyObject& object = getObjectByMyValue("something");
		object.someValue = "something else"; // it doesn't change the value
	}
	catch (...)
	{
		//object not found
	}
}

我的尝试：



我尝试过使用指针并在找不到时返回NULL，但这不起作用。



我也理解退货对象;在其他函数获取它的时候，引用可能超出了这个范围。



我试过谷歌搜索并找到人们使用new来创建另一个对象的例子，但是如果可能，我不想这样做。

What I have tried:

I've tried using pointers and returning NULL when it isn't found also, but that doesn't work.

I also understand that return object; reference may be out of scope here by the time the other function gets it.

I've tried Googling and found examples where people use new to create another object, but I don't want to do that if possible.

推荐答案

在for循环中使用对MyObject的引用：

Use a reference to MyObject in your for loop:

for (MyObject& object : _objects)

避免了问题超出范围的对象变量。



但请允许我说这通常不是一个好习惯为未找到条件抛出异常。这使您的代码更难以使用，并导致相当常见的情况不必要的麻烦。在未找到对象的情况下，返回指针和NULL的方法可能更好。通过上述for循环的修正，它将起作用。

That avoids the problem with the object variable going out of scope.

But allow me the remark that it is usually not a good practice to throw an exception for a "not found" condition. This makes your code more difficult to use and causes unnecessary headaches for a rather common situation. Your approach returning a pointer and NULL in the case that the object has not been found is probably better. And with the above correction of the for loop it will work.

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