Associative array in Delphi , array with string key is possible?

Question

If you work with php you can see the php have associative array (or array width string key) in programing lang. For example:

$server['hostname']  =  'localhost';
$server['database']  =  'test';
$server['username']  =  'root';
$server['password']  =  'password' ;    

// 2d array
$all['myserver']['hostname'] = 'localhost' ;

But can't find any default way to use associative array in delphi.

First I want find default way with out any output component or class . Second if really I cant find with internal way I force choose output classes only.

I use Delphi XE3 , many thanks for your help.

edit: I found one class here : http://www.delphipages.com/forum/showthread.php?t=26334 same as php , but any better way?

A very nice implementation of Associative Array in Delphi can be found here: stackoverflow.com/a/15854846/1022219 . It is closest match to PHP's Assoc Array — iPath ツ
– iPath ツ, Commented Apr 13, 2013 at 10:21

David Heffernan · Accepted Answer · 2012-12-07 15:19:09Z

19

You can use TDictionary<string,string> from the Generics.Collections unit.

var
  Dict: TDictionary<string,string>;
  myValue: string;
....
Dict := TDictionary<string,string>.Create;
try
  Dict.Add('hostname', 'localhost');
  Dict.Add('database', 'test');
  //etc.
  myValue := Dict['hostname'];
finally
  Dict.Free;
end;

And so on and so on.

If you want a dictionary that contains a dictionary, you can do use TDictionary<string, TDictionary<string,string>>.

However, when you do that you'll need to take special care over the lifetime of the dictionary items that are contained in the outer dictionary. You can use TObjectDictionary<K,V> to help manage that for you. You'd create one of these objects like this:

TObjectDictionary<string, TDictionary<string,string>>.Create([doOwnsValues]);

This TObjectDictionary<k,V> operates the same was as a traditional TObjectList with OwnsObjects set to True.

edited Dec 7, 2012 at 15:19

answered Dec 7, 2012 at 15:04

David Heffernan

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7 Comments

A1Gard Over a year ago

here is not complete way i found better in here : delphipages.com/forum/showthread.php?t=26334 , but i want complete class , but Thank you David :)

David Heffernan Over a year ago

I don't understand that comment. What you are looking for are the classes described in my answer.

Ali Avcı Over a year ago

tDictionary was introduced in newer Delphi versions. This solution is far better than the one that I gave with tStrings. Because the implementation of tDictionary is better than tStrings.

Max Carroll Over a year ago

I envy those of you using Delphi 2009 onwards.... I am forced to used TStringList

David Heffernan Over a year ago

@MaxCarroll Yes, that's not very much fun at all!

|

AlexV · Accepted Answer · 2019-10-16 17:56:44Z

14

You can use tStrings and tStringList for this purpose, but 2d arrays are out of the scope of these components.

Usage;

var
  names  : TStrings;
begin
  ...
  names := TStringList.Create;
  ...
  ...
  names.values['ABC'] := 'VALUE of ABC' ;
  ...
  ...
end ;

edited Oct 16, 2019 at 17:56

AlexV

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answered Dec 7, 2012 at 15:06

Ali Avcı

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1 Comment

Max Carroll Over a year ago

should be := (the assignment operator) not = which compares two values/ objects

Maxi-Hard · Accepted Answer · 2016-05-05 11:49:11Z

I had solved the problem that simple way (example):

uses StrUtils;

...

const const_TypesChar : array [0..4] of String =
    (
      'I',
      'F',
      'D',
      'S',
      'B'
    );
const const_TypesStr : array [0..4] of String =
    (
      'Integer',
      'Float',
      'Datetime',
      'String',
      'Boolean'
    );

...

Value := const_TypesStr[ AnsiIndexStr('S', const_TypesChar) ];

// As an example, after execution of this code Value variable will have 'String' value.

//

Then in program we are using two arrays const_TypesChar and const_TypesStr as one associative array with AnsiIndexStr function.

The plus is that it's simple and that we don't need to change code in different places in program every time when we add elements to our arrays.

Ivan Z · Accepted Answer · 2020-03-15 16:37:50Z

0

Look at ArrayS. You can use associative arrays which stores predefined type of data (integer, string, boolean, float), or any of them. For example, below I define an associative array of floats:

uses ArrayS;

var floats : IFltArray;

floats := CreateArray;
floats['first'] := 0.1;
floats['second'] := 0.2;
writeln( floats['second'] );

And so on.

Updated at 2020-03-15

Zipped source code

Ussage example in Russian

edited Mar 15, 2020 at 16:37

answered Aug 13, 2018 at 21:38

Ivan Z

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2 Comments

djdance Over a year ago

404 unfortunately

Ivan Z Over a year ago

The zipped source code and ussage example in Russian.

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