如何根据类属性在向量中找到对象? [英] How can I find an object in a vector based on class properties?

问题描述

I have a class Attribute with the property std::string attributeName. I would like to develop a simple function that returns the index of the Attribute that has an attributeName matching a provided string. Unfortunate restrictions include: I do not have c++0x at my disposal, and I have already overloaded the Attribute == operator for something more complex. Any help would be appreciated, thanks!

edit- I'm very sorry, I realized it is not clear that there is a vector of attributes I am searching in. vector<Attribute> aVec.

解决方案

Use std::find_if with a custom function object:

class FindAttribute
{
    std::string name_;

public:
    FindAttribute(const std::string& name)
        : name_(name)
        {}

    bool operator()(const Attribute& attr)
        { return attr.attributeName == name_; }
};

// ...

std::vector<Attribute> attributes;
std::vector<Attribute>::iterator attr_iter =
    std::find_if(attributes.begin(), attributes.end(),
        FindAttribute("someAttrName"));
if (attr_iter != attributes.end())
{
    // Found the attribute named "someAttrName"
}

---

To do it in C++11, it actually not that different, except you obviously don't need a function object, or have to declare the iterator type:

std::vector<Attribute> attributes;

// ...

auto attr_iter = std::find_if(std::begin(attributes), std::end(attributes),
    [](const Attribute& attr) -> bool
    { return attr.attributeName == "someAttrName"; });

Or if you need to do this multiple times with different names, create the lambda function as a variable, and use std::bind in the call to std::find_if:

auto attributeFinder =
    [](const Attribute& attr, const std::string& name) -> bool
    { return attr.attributeName == name; };

// ...

using namespace std::placeholders;  // For `_1` below

auto attr_iter = std::find_if(std::begin(attributes), std::end(attributes),
    std::bind(attributeFinder, _1, "someAttrName"));

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