add abstract factory

README.md

@@ -15,7 +15,7 @@ A curated collection of idiomatic design & application patterns for Go language.
 
 | Pattern | Description | Status |
 |:-------:|:----------- |:------:|
-| [Abstract Factory](/creational/abstract_factory.md) | Provides an interface for creating families of releated objects | ✘ |
+| [Abstract Factory](/creational/abstract_factory.md) | Provides an interface for creating families of releated objects | ✔ |
 | [Builder](/creational/builder.md) | Builds a complex object using simple objects | ✔ |
 | [Factory Method](/creational/factory.md) | Defers instantiation of an object to a specialized function for creating instances | ✔ |
 | [Object Pool](/creational/object-pool.md) | Instantiates and maintains a group of objects instances of the same type | ✔ |

creational/abstract-factory.md

@@ -0,0 +1,66 @@
+# Abstract Factory Pattern
+
+Abstract Factory creational design pattern provides an interface for 
+creating families of related or dependent objects without specifying
+their concrete classes.
+
+## Implementation
+
+```go
+package afactory
+
+import "fmt"
+
+// Coin hierarchy
+type Coin interface {
+    name() string
+}
+
+type Etherium struct {
+}
+
+type Bitcoin struct {
+}
+
+func (c Etherium) name() string {
+    return "Etherium"
+}
+
+func (c Bitcoin) name() string {
+    return "Bitcoin"
+}
+
+// Abstract Factory implementation
+type AbstractCoinFactory interface {
+    createCoin() Coin
+}
+
+type EtheriumFactory struct {
+}
+
+type BitcoinFactory struct {
+}
+
+func (c EtheriumFactory) createCoin() Coin {
+    return Etherium{}
+}
+
+func (c BitcoinFactory) createCoin() Coin {
+    return Bitcoin{}
+}
+
+```
+
+## Usage
+
+```go
+
+func printNewCoinName (factory AbstractCoinFactory) {
+    coin := factory.createCoin()
+    fmt.Printf("%s\n", coin.name())
+}
+
+printNewCoinName(EtheriumFactory{})
+printNewCoinName(BitcoinFactory{})
+
+```