Index: src/Makefile
==================================================================
--- src/Makefile
+++ src/Makefile
@@ -40,10 +40,11 @@
        OFXMLElementBuilder.m	\
        OFXMLParser.m		\
        unicode.m
 
 INCLUDES := ${SRCS:.m=.h}	\
+	    OFCollection.h	\
 	    ObjFW.h		\
 	    asprintf.h		\
 	    ${ATOMIC_H}		\
 	    macros.h		\
 	    objfw-defs.h	\

Index: src/OFArray.h
==================================================================
--- src/OFArray.h
+++ src/OFArray.h
@@ -10,10 +10,11 @@
  */
 
 #include <stdarg.h>
 
 #import "OFObject.h"
+#import "OFCollection.h"
 #import "OFEnumerator.h"
 
 @class OFDataArray;
 @class OFString;
 
@@ -22,11 +23,12 @@
 #endif
 
 /**
  * \brief A class for storing objects in an array.
  */
-@interface OFArray: OFObject <OFCopying, OFMutableCopying, OFFastEnumeration>
+@interface OFArray: OFObject <OFCopying, OFMutableCopying, OFCollection,
+    OFFastEnumeration>
 {
 	OFDataArray *array;
 }
 
 /**
@@ -112,15 +114,10 @@
  * \return An initialized OFArray
  */
 - initWithCArray: (id*)objs
 	  length: (size_t)len;
 
-/**
- * \return The number of objects in the array
- */
-- (size_t)count;
-
 /**
  * \return The objects of the array as a C array
  */
 - (id*)cArray;
 
@@ -180,15 +177,10 @@
  * \param separator The string with which the objects should be joined
  * \return A string containing all objects joined by the separator
  */
 - (OFString*)componentsJoinedByString: (OFString*)separator;
 
-/**
- * \return An OFEnumerator to enumarate through the array's objects
- */
-- (OFEnumerator*)objectEnumerator;
-
 #ifdef OF_HAVE_BLOCKS
 /**
  * Executes a block for each object.
  *
  * \param block The block to execute for each object

ADDED   src/OFCollection.h
Index: src/OFCollection.h
==================================================================
--- src/OFCollection.h
+++ src/OFCollection.h
@@ -0,0 +1,31 @@
+/*
+ * Copyright (c) 2008 - 2010
+ *   Jonathan Schleifer <js@webkeks.org>
+ *
+ * All rights reserved.
+ *
+ * This file is part of ObjFW. It may be distributed under the terms of the
+ * Q Public License 1.0, which can be found in the file LICENSE included in
+ * the packaging of this file.
+ */
+
+#import "OFEnumerator.h"
+
+/**
+ * \brief A protocol with methods common for all collections.
+ */
+@protocol OFCollection
+#ifdef OF_HAVE_PROPERTIES
+@property (readonly) size_t count;
+#endif
+
+/**
+ * \return The number of objects in the collection
+ */
+- (size_t)count;
+
+/**
+ * \returns An OFEnumerator to enumerate through all objects of the collection
+ */
+- (OFEnumerator*)objectEnumerator;
+@end

Index: src/OFDictionary.h
==================================================================
--- src/OFDictionary.h
+++ src/OFDictionary.h
@@ -10,10 +10,11 @@
  */
 
 #include <stdarg.h>
 
 #import "OFObject.h"
+#import "OFCollection.h"
 #import "OFEnumerator.h"
 
 @class OFArray;
 
 #ifdef OF_HAVE_BLOCKS
@@ -30,22 +31,18 @@
 /// \endcond
 
 /**
  * \brief A class for storing objects in a hash table.
  */
-@interface OFDictionary: OFObject <OFCopying, OFMutableCopying,
+@interface OFDictionary: OFObject <OFCopying, OFMutableCopying, OFCollection,
     OFFastEnumeration>
 {
 	struct of_dictionary_bucket **data;
 	uint32_t size;
 	size_t count;
 }
 
-#ifdef OF_HAVE_PROPERTIES
-@property (readonly) size_t count;
-#endif
-
 /**
  * Creates a new OFDictionary.
  *
  * \return A new autoreleased OFDictionary
  */
@@ -154,20 +151,10 @@
  * \param key The key whose object should be returned
  * \return The object for the given key or nil if the key was not found
  */
 - (id)objectForKey: (id)key;
 
-/**
- * \return The number of objects in the dictionary
- */
-- (size_t)count;
-
-/**
- * \returns An OFEnumerator to enumerate through the dictionary's objects
- */
-- (OFEnumerator*)objectEnumerator;
-
 /**
  * \return An OFEnumerator to enumerate through the dictionary's keys
  */
 - (OFEnumerator*)keyEnumerator;