inserting data in nested STL maps

Code:

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std :: map <QString, std :: vector <std :: pair <QString, QString> > > configFileDataVector;

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The examples on Google show the insertion techniques on non-nested maps, I tried this:

Code:

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configFileDataVector.insert (std::make_pair ("fdsf", ("Peter Q.","5328")));

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It shows a warning:

Quote:

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left-hand operand of comma has no effect

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It may be simple, but somehow nothing is striking me at this moment,
Please guide.

Quote:

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left-hand operand of comma has no effect

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that's because

Code:

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("Peter Q.","5328")

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is basically meaningless to the compiler.

think about it. you are inserting into a std::map<QString, std::vector<std:: pair<QString, QString> > >. the value portion of the map is a std:: pair, so you need to insert it as such. the compiler cannot automatically deduce that ("Peter Q.","5328") is a std:: pair.

you're very close, but you need to be explicit (like always) about what you're inserting as the value of the std:: pair.

Thanks for replying,

Code:

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configFileDataVector.insert (std::make_pair ("fdsf", std::make_pair ("Peter Q.","5328")));

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Is this what you mean? I can try that out tomorrow morning only!

yes, that's exactly what I mean. that should solve your problem.

That wont quite work. The mapped type is a vector of pairs, not just a pair by itself. You'd need:

Code:

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configFileDataVector.insert(std::make_pair("fdsf", std::vector(1, std::make_pair("Peter Q.", "5328"))));

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However, I'd suggest simply doing this instead:

Code:

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configFileDataVector["fdsf"].push_back(std::make_pair("Peter Q.", "5328"));

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Note that this assumes that the key value doesn't currently map to a non-empty vector, or that you actually intend to insert multiple items into the vector in this manner.

Quote:

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Originally Posted by iMalc

That wont quite work. The mapped type is a vector of pairs, not just a pair by itself.

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good catch... I didn't see the vector in there.

typedefs are your friend when working with the STL. Using them will alleviate a lof of confusion.

Quote:

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Originally Posted by iMalc

You'd need:

Code:

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configFileDataVector.insert(std::make_pair("fdsf", std::vector(1, std::make_pair("Peter Q.", "5328"))));

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However, I'd suggest simply doing this instead:

Code:

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configFileDataVector["fdsf"].push_back(std::make_pair("Peter Q.", "5328"));

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This did the trick, than you for bothering, this was simple but I probably was not putting much effort in figuring it out, thanks again. I followed your second way.

I also got some error messages which I couldn't even read properly, leave alone understanding, :rolleyes:

Thanks to all others who responded.