Apa iku pola Singleton?

Question

Accepted Answer

Pola **Singleton** mesthikake sawijining kelas mung duwe **siji instance** lan nyedhiyakake titik akses global kanggo melu. Digunakake nalika persis siji obyek kudu ngatur samubarang (konfigurasi, connection pool, logger), sanajan uga dadi kontroversi.

## Apa sing ditindakake Singleton

```text
SINGLETON → guarantee a class has only ONE instance, with global access to it:
  → the class controls its own instantiation (private constructor)
  → returns the SAME instance every time it's requested
→ for: things there should only be ONE of, accessed from many places
```

## Conto

```js
class Config {
  static #instance;
  static getInstance() {
    if (!Config.#instance) {
      Config.#instance = new Config();   // create once
    }
    return Config.#instance;             // always return the same instance
  }
}
// Config.getInstance() always returns the same object
```

## Panggunaan umum lan kontroversi

```text
USES → configuration objects, loggers, connection pools, caches (one shared instance)
⚠️ CONTROVERSIAL → Singletons are often criticized:
  → GLOBAL STATE in disguise → hidden dependencies, hard to TEST (can't easily mock/replace),
    tight coupling, issues with concurrency
  → often better: DEPENDENCY INJECTION (pass the single instance in) → same "one instance"
    benefit but testable and explicit
→ use sparingly; consider DI as an alternative; valid for genuinely-single resources
```

## Mengapa iku penting

Pamahaman babagan pola Singleton iku berharga amarga iku salah sijining **pola desain sing paling dikenal** (sering ketemu lan dirembug), lan pemahamane — kalebu kontroversinipun — nggambarake keputusan desain sing apik.

Singleton mesthikake kelas mung duwe siji instance kanthi akses global, digunakake nalika kuwi bener-bener kudu ana mung siji saka samubarang (konfigurasi, logger, connection pool, cache) sing diakses saka pirang-pirang papan.

Pamahaman apa sing ditindakakake (kelas kontrol inisiasinipun dhewe kanggo menggae instance sing padha saben wektu) iku kawruh dhasar.

Nanging, pamahaman babagan **kontroversinipun** uga penting lan nggambarake keputusan kang mature: Singleton sering dikritik amarga dheweke iku sejatine **global state sing kamuflase**, nggawa **hidden dependencies** (kode nggunakake Singleton duwe dependensi sing ora dideklarasikake), nggawe kode **angel ditesting** (ora bisa gampang mock utawa ngganti single instance), nyebabake tight coupling, lan nggawa masalah concurrency.

Pamahaman manawa **dependency injection sering dadi alternatif sing luwih apik** (njajal single instance, nyedhiyakake benefit "siji instance" sing padha nanging cara sing testable, eksplisit) nggambarake keputusan desain kanggo milih DI tinimbang Singleton ing pirang-pirang kasus.

Pamahaman seimbang iki — ngerti pola nanging uga probleminipun lan alternatif sing luwih apik — iku sing beda pamakean sing atine saka cargo-culting.

Suwene Singleton iku salah sijining pola sing paling dikenal lan sering dirembug, lan suwene pemahamane ing karo kontroversi signifikan (global state, masalah testability) lan alternatif dependency-injection nggambarake keputusan desain mature sing bedakake developer sing atine, lan topik sing sering ketemu lan dirembug ing desain software.