User:Nhollm

Basic syntax

program Example;

uses
Generics.Collections;  //import the generics-library of the RTL

type
TStringStringDictionary =  specialize TDictionary<string, string>; //specialize a new dictionary and set the data-type of key and value

var
  MyDictionary : TStringStringDictionary;
begin
  MyDictionary := TStringStringDictionary.Create;
  try
    //do stuff with your dictionary..
  finally
    MyDictionary.Free;
  end;
end.

Source Code

{$mode objfpc}

program Example;

uses
Generics.Collections  //import the generics-library of the RTL

type

TStringStringDictionary =  specialize TDictionary<string, string>; //specialize a new dictionary and set the data-type of key and value

var
  MyDictionary : TStringStringDictionary;
  TestClass : TmyCoolClass;
  //
  KeyString: string;
  KeyValuePair : TStringStringDictionary.TDictionaryPair;
  SearchedValue : string;
begin

   //create the dictionary
   MyDictionary := TStringStringDictionary.Create;

   //Add Element or update its value to new (key, value)
   MyDictionary.AddOrSetValue('Key1', 'Value1');

   //Remove Element
   MyDictionary.AddOrSetValue('Key2', 'Another Value');
   MyDictionary.Remove('Key2');


   //Clear entire dictionary
   MyDictionary.Clear;

   // Total number of Items in dictionary (count)
   writeln('Items in Dictionary: ' + IntToStr(MyDictionary.Count));

   //Get Value by Key
   writeln(MyDictionary.Items['Key1'].Name);  //If the provided key does not exist, this will throw a Error :'Dictionary Key does not Exist'


   //----------------------Trying------------------


   //TryAdd  returns True if added successfully, False otherwise
    writeln('TryAdd: ' + BoolToStr(MyDictionary.TryAdd('Key2',TestClass ),'True', 'False'));

   //'TryGetValue'takes two Arguments ->(key, value) and returns a boolean.
   //If found, it returns true and the provided 'value' variable becomes the value of the searched KeyValuePair
   //if not found,the function returns False and the provided 'value'-variable is nil
   writeln(BoolToStr(MyDictionary.TryGetValue('Key', SearchedValue)));
   if MyDictionary.TryGetValue('Key', SearchedValue) then
        writeln('Key found. Its Value is ' + SearchedValue.Name )
   else
       if SearchedValue = Nil then
          writeln('the provided Value is Nil now');


   //----------------------Loop through the Dictionary------------------

   //Loop Keys
   for KeyString in MyDictionary.Keys do
        writeln('Found key:' + KeyString);


   //Loop Values
   for TestClass in MyDictionary.Values do
        writeln('Found Value:' + TestClass.Name);


   //Loop Key-Value-Pairs
   for KeyValuePair in MyDictionary do
        writeln('Found a Pair: Key:' + KeyValuePair.Key + ' Value:' + KeyValuePair.Value.Name);



    //----------------------Check if.. exists in whole Dictionary------------------

   //Check if Key exists
   if MyDictionary.ContainsKey('Key1') then
      writeln('key exists')
   else
       writeln('key not found');


   //Check if Value exists
   if MyDictionary.ContainsValue(TestClass) then
      writeln('value exists')
   else
       writeln('value not found');


   readln() //for Windows-console-users
end.