In this first developer-themed post, I am going to describe some basic stuff, before I delve into some real-world applications.
Delphi 2009 brought Generics to the Delphi-World. And since then, they are found in all of my Applications. Especially Generics.Collections are heavily used by me.
Before Generics.Collections I had to implement a TList for each Class I would like to store a variable amount of Objects. (Or I could use Contnrs.TObjectList and cast to TAnimal everytime I need one, but I don't find that very desirable)
And this is just for TAnimal, if there are any other classes, I would have to copy&paste the code for the List and replace the data types.
With Generics.Collections the same thing looks like this:
And I don't even need the alias "TAnimalList", I could use "TList<TAnimal>" instead.
Also, it is not limited to Classes, it can hold every datatype like integer, double, boolean and even records. In my case it is even better to use TObjectList<TAnimal>, which automatically frees its containing objects if it is freed.
Since all the Generics.Collectionshave an Enumerator the following is possible:
Generics.Collections has more then some simple Lists up its sleeve. There are also TQueue, which uses FIFO and TStack which uses LIFO to store its contents.
TDictionary is a little different, because its taking two type parameters. One for the key, one for the Value.
A case that I often stumble upon is to store (and recieve) some object or value for a specific string. And then I always use a TDictionary<String,TValue>
There's also a TObjectDictionary, which takes care of memory of the keys, the values or even both.
That's it for today.
Delphi 2009 brought Generics to the Delphi-World. And since then, they are found in all of my Applications. Especially Generics.Collections are heavily used by me.
Before Generics.Collections I had to implement a TList for each Class I would like to store a variable amount of Objects. (Or I could use Contnrs.TObjectList and cast to TAnimal everytime I need one, but I don't find that very desirable)
interface
uses
Classes;
type
TAnimal = class
private
fName : string;
public
property Name : string read fName write fName;
end;
TAnimalList = class (TList)
private
procedure putAnimal(Index : integer; Value : TAnimal);
function getAnimal(Index : integer) : TAnimal;
public
property Items [Index : integer] : TAnimal read getAnimal write setAnimal;
end;
implementation
procedure TAnimalList.putAnimal(Index : integer; Value : TAnimal);
begin
inherited put(Index, Value);
end;
function TAnimalList.getAnimal(Index : integer) : TAnimal;
begin
result := (TAnimal) inherited get(Index);
end;And this is just for TAnimal, if there are any other classes, I would have to copy&paste the code for the List and replace the data types.
With Generics.Collections the same thing looks like this:
interface
uses
Generics.Collections;
type
TAnimal = class
private
fName : string;
public
property Name : string read fName write fName;
end;
TAnimalList = TList<TAnimal>And I don't even need the alias "TAnimalList", I could use "TList<TAnimal>" instead.
Also, it is not limited to Classes, it can hold every datatype like integer, double, boolean and even records. In my case it is even better to use TObjectList<TAnimal>, which automatically frees its containing objects if it is freed.
Since all the Generics.Collectionshave an Enumerator the following is possible:
var
fAnimals : TList<TAnimal>
procedure init;
var
a : TAnimal;
begin
for a in fAnimals do
begin
a.DoSomething;
end;
end;Generics.Collections has more then some simple Lists up its sleeve. There are also TQueue, which uses FIFO and TStack which uses LIFO to store its contents.
TDictionary is a little different, because its taking two type parameters. One for the key, one for the Value.
A case that I often stumble upon is to store (and recieve) some object or value for a specific string. And then I always use a TDictionary<String,TValue>
There's also a TObjectDictionary, which takes care of memory of the keys, the values or even both.
procedure init; var ownsKeys, ownsValues, ownsBoth : TObjectDictionary<TKey, TValue> begin ownsKeys := TObjectDictionary<TKey, TValue>.Create([doKeys]); ownsValues := TObjectDictionary<TKey, TValue>.Create([doValues]); ownsBoth := TObjectDictionary<TKey, TValue>.Create([doKeys, doValues]); end;
That's it for today.
