Apa iku pola Command?

Question

IT Interview Practice · Accepted Answer

Pola **Command** ngenkapsulasi **njaluk minangka obyek** — ngowahi aksi dadi obyek mandiri sing duwe kabeh informasine. Iki ndadekake bisa antri, ngelog, undo/redo, lan mbutsake panjaluk saka sing ngleksani.

## Apa sing ditindakake pola Command

```text
COMMAND → encapsulate an action/request as an OBJECT (with its data and an execute method):
  → a command object knows WHAT to do and has the info to do it
  → the invoker triggers commands without knowing their details
  → decouples the object that INVOKES from the object that PERFORMS the action
→ "turn an action into an object" → store, pass, queue, log, undo it
```

## Conto

```js
// commands encapsulate actions
class AddTextCommand {
  constructor(doc, text) { this.doc = doc; this.text = text; }
  execute() { this.doc.add(this.text); }
  undo() { this.doc.remove(this.text); }   // commands can support undo
}
// invoker executes and tracks commands (for undo/redo)
const cmd = new AddTextCommand(doc, 'hello');
cmd.execute();
cmd.undo();   // reverse it
```

## Apa sing diwenehake

```text
✓ UNDO/REDO → store executed commands; call undo()/redo() (each command knows how to reverse)
✓ QUEUING → queue commands to execute later; schedule; batch
✓ LOGGING → log commands (e.g. for replay, audit, transactions)
✓ DECOUPLING → invoker doesn't know the command's implementation (just calls execute())
USES → undo/redo (editors), task queues/jobs, transactional operations, action objects
  (e.g. Redux actions), macro recording, GUI buttons/menu items triggering commands
```

## Mengapa iki penting

Ngerteni pola Command kuwi berharga amarga iku **pola behavioral sing migunani** sing ndadekake kemampuan penting kaya undo/redo lan antri, mula iku pengetahuan desain sing relevan.

Pola Command ngenkapsulasi njaluk minangka obyek — ngowahi aksi dadi obyek mandiri sing duwe datane lan metode execute, mbutsake panjaluk saka sing ngleksani.

Ngerteni apa sing ditindakake (makili aksi minangka obyek sing ngerti apa sing kudu ditindakake, karo invoker ngatak perintah tanpa ngerti detaile) iku pengetahuan intinya.

Ngerteni **apa sing diwenehake** iku nilai utamane: **undo/redo** (nyimpen perintah sing wis ditindakake lan manggil undo/redo, saben perintah ngerti cara balik dhirine — kasus paling klasik lan kuat kanggo editor lan aplikasi), **antri** (antri perintah kanggo ditindakake mengko, jadwal, utawa batch), **logging** (nolog perintah kanggo diputar maneh, audit, utawa transaksi), lan **mbutsake** (invoker ora ngerti apa implementasine perintah).

Kemampuan-kemampuan iki — utamane undo/redo lan antri — bener-bener berharga lan susah diwujudake kanthi apik tanpa pola Command.

Ngerteni **panggunaan** — undo/redo ing editor, task queue lan background job, operasi transaksional, action object (kaya Redux action, conto modern sing luwes), macro recording, lan elemen GUI ngatak perintah — iku njlentrehake diterapno ing dunyo nyata.

Pola Command iku cara sing apik kanggo ngewujudake undo/redo, antri, lan arsitektur berbasis aksi.

Kamroa pola Command ndadekake kemampuan penting (undo/redo, antri, logging, mbutsake) sing berharga lan susah diwujudake kanthi apik ing cara liyane, lan amarga iku tampil ing sistem nyata (editor, task queue, Redux action), lan amarga ngerteni apa sing ditindakake lan diwenehake iku relevan kanggo ngewujudake kemampuan-kemampuan iki, ngerteni pola Command iku pengetahuan desain sing berharga lan praktikal — pola migunani sing ndadekake undo/redo, antri, lan arsitektur berbasis aksi (kaya Redux action), cara apik kanggo ngewujudake kemampuan berharga iki, lan pengetahuan desain penting kanggo aksi sing kudu disimpen, diatur antri, dilog, utawa diundeni.

Apa sing ditindakake pola Command

Conto

Apa sing diwenehake

Mengapa iki penting

Pitakon sing gegandhengan