从迭代器返回对象的引用

问题描述

我想从向量返回对象的引用，并且该对象位于迭代器对象中。我怎么能这样做？

I want to return a reference of an object from a vector, and the object is in an iterator object. How can I do that?

我尝试了以下内容：

Customer& CustomerDB::getCustomerById (const string& id) {
    vector<Customer>::iterator i;
    for (i = customerList.begin(); i != customerList.end() && !(i->getId() == id); ++i);

    if (i != customerList.end())
        return *i; // is this correct?
    else
        return 0; // getting error here, cant return 0 as reference they say
}

在代码中，customerList是客户的向量，函数getId返回客户的id。

In the code, customerList is a vector of customers, and the function getId returns the id of the customer.

是 * i 对吗？如何返回0或null作为参考？

Is the *i correct? And how can I return 0 or null as a reference?

推荐答案

return * i; 是正确的，但是你不能返回0或任何其他这样的值。如果在向量中找不到Customer，请考虑抛出异常。

return *i; is correct, however you can't return 0, or any other such value. Consider throwing an exception if the Customer is not found in the vector.

在向量中返回对元素的引用时也要小心。如果向量需要重新分配其内存并移动内容，则在向量中插入新元素可能会使引用无效。

Also be careful when returning references to elements in vector. Inserting new elements in vector can invalidate your reference if vector needs to re-allocate its memory and move the contents.

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