Editing values of a Map

I have inserted some values in a C++ Map, now I want to edit the value associated with a key. I can insert and delete but how to edit?

Any hints?

I have tried this:

Code:

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map <unsigned int, QTcpSocket*> :: iterator objTempIter;

objTempIter = mapName.end ();
(*objTempIter).first = 22;

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This gives me an error:

Code:

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error: assignment of read-only data-member ‘std::pair<const unsigned int, QTcpSocket*>::first’

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Code:

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yourMap["keyName"] = newValue;

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Or something like that.

Thanks for replying,

Q: Can I edit the key itself?

Q: The value associated with the key is a socket pointer, so even if I exchange the positions of the current key and its value somehow, then how will I write the keyname according to your example in post 2?

Sorry, i don't have any experience with C++'s map class.

What i can tell you is that in the code you've tried it says that "first" can't be changed. That's your problem.

Quote:

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Originally Posted by AnishaKaul

Thanks for replying,

Q: Can I edit the key itself?

Q: The value associated with the key is a socket pointer, so even if I exchange the positions of the current key and its value somehow, then how will I write the keyname according to your example in post 2?

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Just like every other container, .end() is not an actual element of your map, but rather "one past the last valid item".

If you want to change the key value, you will have to map the QSocket* to the new int, then remove the previous map element (with something like remove()).

Thanks TabStop, but I didn't understand the following:

Quote:

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map the QSocket* to the new int

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Basically, it just means that you add a new element to the map and remove the old one. In this case, adding a new element means that your new integer key will map to the same QTcpSocket pointer as the old integer key.

I am sorry if I am missing your point again, but did you mean that the previous entry which I want to be edited should be removed and then a fresh entry with the fresh data should be made?

Quote:

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Originally Posted by AnishaKaul

did you mean that the previous entry which I want to be edited should be removed and then a fresh entry with the fresh data should be made?

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Yes, if you want to change the key.

Thank you for that, if I have further queries I'll post here again.