CODEWITHSUNDEEP
c++vectorstruct
smyslov
smyslov

Reputation: 1275

Search for a struct element in vector by id and return name

I have a struct as follows: 

struct deviceDescription_t
{
    std::string deviceID;
    std::string deviceDescription;
};

I have defined a vector as follows: 

std::vector<deviceDescription_t> deviceList

Let's say the vector deviceList is made up of the following elements:

ID    Description
=================
one_1  Device 1
two_2  Device 2
three_3 Device 3
....

I need to search through the ID field in deviceList and get the description for this. Let's say I have one as the predicate (search string). I now have to look through the ID field in the deviceList to find a match which I am doing by using 

std::string temp = deviceID.substr(0, deviceID.find("_"));

but I am not sure how to use the find_if mentioned in this question.

As one answer, it is advised to use

auto iter = std::find_if(deviceList.begin(), deviceList.end(),
            [&](deviceDescription_t const & item) {return item.deviceID == temp;});

Using the above in my function, throws the following error

Local class, struct or union definitions are not allowed in a member function of a managed class.

Could anyone please guide me on how to use find_if to find the element matching the search criteria and return the description?

Upvotes: 3

Views: 1717

Answers (1)

Andy
Andy

Reputation: 30418

Based on the error message, it sounds like you have a C++/CLI project.

When a lambda is used inline like you have in the call to find_if(), it is really creating a small class for you that overrides operator (). Unfortunately the only way to call find_if() from a managed class is to do that yourself:

struct DeviceFinder
{
public:
    DeviceFinder(const std::wstring& temp)
    : m_temp(temp)
    {
    }

    bool operator() (const deviceDescription_t& item) const
    {
        return item.deviceID == m_temp;
    }

private:
    const std::wstring& m_temp;
};

And then you would call find_if() like this:

auto iter = std::find_if(deviceList.begin(), deviceList.end(),
                         DeviceFinder(temp));

Upvotes: 2

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