Add Formatter abstract superclass (#132)

source/Buoy-Collections-Tests/CollectionFormatterTest.class.st

@@ -72,3 +72,9 @@ CollectionFormatterTest >> testFormatWithLastSeparator [
 	formatter := CollectionFormatter separatingWith: ', ' andLastWith: ' and '.
 	self assert: (formatter format: #(1 2 3)) equals: '1, 2 and 3'
 ]
+
+{ #category : 'tests' }
+CollectionFormatterTest >> testIsAbstract [
+
+  self deny: CollectionFormatter isAbstract
+]

source/Buoy-Collections/CollectionFormatter.class.st

@@ -6,7 +6,7 @@ Implementation Notes:
 "
 Class {
 	#name : 'CollectionFormatter',
-	#superclass : 'Object',
+	#superclass : 'Formatter',
 	#instVars : [
 		'separator',
 		'elementFormatter',
@@ -61,12 +61,6 @@ CollectionFormatter class >> separatingWith: aSeparator applyingToEach: anElemen
 		applyingToEach: anElementFormatter
 ]
 
-{ #category : 'formatting' }
-CollectionFormatter >> format: aCollection [
-
-	^ String streamContents: [ :stream | self format: aCollection on: stream ]
-]
-
 { #category : 'formatting' }
 CollectionFormatter >> format: aCollection on: aStream [
 

source/Buoy-Collections/Formatter.class.st

@@ -0,0 +1,29 @@
+"
+I'm an abstract class for formatters.
+
+A formatter is an object that knows how to convert a given object into a string representation.
+"
+Class {
+	#name : 'Formatter',
+	#superclass : 'Object',
+	#category : 'Buoy-Collections',
+	#package : 'Buoy-Collections'
+}
+
+{ #category : 'testing' }
+Formatter class >> isAbstract [
+
+  ^ self = Formatter
+]
+
+{ #category : 'formatting' }
+Formatter >> format: aCollection [
+
+	^ String streamContents: [ :stream | self format: aCollection on: stream ]
+]
+
+{ #category : 'formatting' }
+Formatter >> format: object on: stream [
+
+  self subclassResponsibility
+]