Qt and finding partial matches in a QList

Question

I have a struct viz:

struct NameKey
{
    std::string      fullName;
    std::string      probeName;
    std::string      format;
    std::string      source;
}

which are held in a QList:

QList<NameKey> keyList;

what I need to do is find an occurence in keyList of a partial match where the search is for a NameKey that only has two members filled. All the keyList entries are full NameKey's.

My current implementation is , well, boring in the extreme with too many if's and conditions.

So, If I have a DataKey with a fullName and a format I need to find all the occurences in keyList which match. Any useful Qt/boost things available?

Answer 1

Just a note: any solution that uses a list has O(n) time complexity, at least.

One option is to use QString, instead of std::string, and take advantage of their regular expressions built-in support.

Example:

#include <QList>
#include <QString>
#include <QRegExp>

struct NameKey
{
    QString    fullName;
    QString    probeName;
    QString    format;
    QString    source;
};

QList<NameKey>  keyList; // <--

void Foo() {
   QRegExp  reg("pattern"); // <-- prepare a regular expression (format)
   NameKey  nk;
   foreach (nk, keyList) {
      if (nk.fullName.contains(reg)) {
         // a match ...
         break;
      }
      // ...
   }
}

Answer 2

Similar to Nick D's answer:

#include <QList>
#include <QString>
#include <QRegExp>

struct NameKey
{
    QString    fullName;
    QString    probeName;
    QString    format;
    QString    source;

    bool containsPattern(const QRegExp &pattern) {
       return fullName.contains(reg) ||
              probeName.contains(reg) ||
              format.contains(reg) ||
              source.contains(reg);
    }
};

QList<NameKey> matches(const QList<NameKey> &keyList, const QString &pattern) {
   QRegExp  reg(pattern);
   QList<NameKey> matches;
   foreach (NameKey nk, keyList) {
      if (nk.containsPattern(reg))
         matches << nk;
   }
   return matches;
}

There are obviously many ways to do this. I like to put as much intelligence into data structures as possible.

Answer 3

QList is compatible with STL. So you can use it with STL algorithm:

struct NameKeyMatch {
    NameKeyMatch(const std::string & s1, const std::string & s2, const std::string & s3, const std::string & s4)
    : fullName(s1), probeName(s2), format(s3), source(s4) {}

    bool operator()(const NameKey & x) const
    {
        return  fullName.size() && x.fullName == fullName &&
                probeName.size && x.probeName == probeName &&
                format.size && x.format == format &&
                source.size && x.source == source;
    }

    std::string fullName;
    std::string probeName;
    std::string format;
    std::string source;
};

QList<int>::iterator i = std::find_if(keyList.begin(), keyList.end(), NameKeyMatch("Full Name", "", "Format", ""));

I don't know if Qt will actively maintain STL compatibility though.