R – TDictionary – invalid key

delphidelphi-2009tdictionary

I have code like this:

type
  TMyDictionary = TDictionary<int, int>;

var
  myDict: TMyDictionary;
  k, v: integer;

  // code to fill the dictionary

  for k in myDict.Keys do
  begin
     v := myDict.Items[k];

     // other stuff
  end;

Randomly I see an exception thrown on 'v := myDict.Items[k];' which says k is invalid.

Anyone else seen this?

Best Answer

Are you modifying myDict inside the section labeled // other stuff?

Related Solutions

Delphi – How to List a TDictionary in Alphabetical Order by Key in Delphi 2009

The dictionary is a hash table, so it doesn't store items in sorted order. TEnumerator is simple - it just a means of iterating over items.

To get items in an order, you need to sort them. One way would be to put them into a list and sort the list, like this:

var
  list: TList<string>;
begin
  list := TList<string>.Create(Dic.Keys);
  try
    list.Sort;
    // process sorted list of items now
  finally
    list.Free;
  end;
end;

Delphi – How to get the key from a TDictionary

Use an enumerator.

for Key in MyDictionary.Keys do
  ShowMessage(Key.AStringProperty);

Since TDictionary is a hash table, you can't access it with integer indexing like an array or TList. But an enumerator works just fine.

Best Answer

Related Solutions

Delphi – How to List a TDictionary in Alphabetical Order by Key in Delphi 2009

Delphi – How to get the key from a TDictionary

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